Another Auto Transmission Problem [Merged]

[Dangermouse]

Well, my week has been going spiffingly :sad30:, so it now looks like I may be finally getting into this.:swear1:

I was down at my local RS picking up components, but the Tantalum caps they had in stock were the wrong ratings. (I assume that a 10uF 16V is no good)

They had the correct sizes in Electrolytic though. Is the recommendation for Tantalum for the technology or the physical size?

[Ron]

That would be correct for one of the two caps that give the most problem, but the other is 4.7uF.

See post 1, 2nd pic in 3rd row here (http://dmctalk.org/showthread.php?350-Automatic-Transmission-Governor) for part specs.

[WelmoedJ]

Well, my week has been going spiffingly :sad30:, so it now looks like I may be finally getting into this.:swear1:

I was down at my local RS picking up components, but the Tantalum caps they had in stock were the wrong ratings. (I assume that a 10uF 16V is no good)

They had the correct sizes in Electrolytic though. Is the recommendation for Tantalum for the technology or the physical size?

I replaced my electrolitic with tantalum at the time, using 35V versions.
Better a bit over-rated in the Voltage area than underrated like the originals.
Tantalum indeed is the way to go.

Are you also going to replace the transitors and the resistors that are in the transistor circuit?
Transistors are TIP41C and I used a bit more powerful resistors (2W instead of 1W).

[Dangermouse]

Sorry, my post was a little vague.

I picked up the following

10uF 35V Electrolytic cap
4.7uF 35V Electrolytic cap
TIP42 transistors (2 off) - 65W - based on Ron's note above that would make them TIP42B

I didn't get the resistors, as Elvis noted that they never need changing, but maybe I should go back and pick them up.

My concern is that they are this style and whether there will be physical room to mount them

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTrhhR_2YWmAGJw98oHv2lLvwW57zVe0 p1Ac6-M_rwe4RdNqRnc_A

They only had two tantalum sizes (0.1uF 35V and 10uF 16V) so I didn't buy those.

[Ron]

+1 on tantalum!

But be careful...a TIP41C is NPN and a TIP42C in PNP.
I have seen TIP41C on some of the old schematics but have never found one on a board.

EDIT: The parts list has some substitutes...
IMHO, if the resistors measure out, it isn't worth the risk messing with them on these crappy boards...

[Dangermouse]

My question is: are the Electrolytic ones OK to use, as my local RS doesn't stock the tantalum ones?

(btw - I want/need to look at this, this evening)

[Bitsyncmaster]

My question is: are the Electrolytic ones OK to use, as my local RS doesn't stock the tantalum ones?

(btw - I want/need to look at this, this evening)

Electrolytic should be fine since they were probably electrolytic in the first place but tantalum are more reliable. Tantalum caps get expensive when you need higher capacitance and higher voltage. We still use electrolytic in those locations.

[jawn101]

...(I assume that a 10uF 16V is no good)

Just don't end up with one of these :)

http://www.discovercircuits.com/dc-mag/Issue_4/Photos/FakeCapacitor1.jpg

[David T]

Electrolytic should be fine since they were probably electrolytic in the first place but tantalum are more reliable. Tantalum caps get expensive when you need higher capacitance and higher voltage. We still use electrolytic in those locations.

Tantalium is the better way to go because they do not seem to age and fail like an ordinary electrolytic. They are also not sensitive to polarity so you can't install them backwards. If the boards shift at all you should not replace the transistors or the resistors. Those components fail solid so if they work at all they are OK. Usually burnt up when the wiring gets melted and you short to ground. The caps just fail due to age making the shifting erratic. The thermal sensitivity is due to the bad solder joints.
David Teitelbaum

[Bitsyncmaster]

Tantalium is the better way to go because they do not seem to age and fail like an ordinary electrolytic. They are also not sensitive to polarity so you can't install them backwards. If the boards shift at all you should not replace the transistors or the resistors. Those components fail solid so if they work at all they are OK. Usually burnt up when the wiring gets melted and you short to ground. The caps just fail due to age making the shifting erratic. The thermal sensitivity is due to the bad solder joints.
David Teitelbaum

Tantalium is polarity marked. I've blown many installing them backwards. They do blow apart and make a mess.

[Dangermouse]

I decided to start afresh from deloumis's similarly named thread to keep them separate

Transmission is staying in 2nd or 3rd. Don't know which one.

Over the past couple of weeks it has occasionally started off in 2nd or 3rd (not first). My center console is out or the car so I initially put it down to selecting 2 instead of D (and perhaps I was) as there is really no way to tell if you aren't paying attention. No markings. Car gets up to speed and then starts to shift normally. Maybe a couple of days pass before it does it again.

Yesterday on the way to the tire shop, it starts off OK (1-2-3) but at some point it stops going into 1st completely.

I was convinced that it was the governor, so I stocked up on capactitors and transistors, ready to get stuck in tonight. Before I did, I put my light box on and found that both LEDs stay on all the time (P, D, 2, 1). They also stay on when I pull fuse 13. Based on previous threads I understand this to mean that the governor is not the problem.

Checked Fuse 13 for continutity and is OK.

Found a little oxidation in the L shaped connectors on top of the black box on the firewall (don't know what it is called). Also cleaned all the church window connectors on the passenger side. Nothing of real note.

Checked the routing of the three cables from the black connection box. (two large and one smaller) The large one to the GC is good - no signs of melting. The other large one to the sensor on the passengers side of the transmission is good also (what is this sensor?).The smaller one (with the blue/green/brown connectors on top) that goes to the sensor on the drivers side (again, what is this sensor?) has heat damage, but it was noted a couple of years ago and tied up out of the way. Not sure if that is relevant.

Recent background - Did a transmission drain and fill a couple of weeks ago. Put in 4.5 qts, so the level is to the bottom of the spiral. Maybe a little full? The occasional starting-in-second pre-dated this drain and fill.

Are there any other connections that I should look at? What's next in the likelihood of failure?

EDIT: I merged your posts to keep all the info together.
-Ron

[Dangermouse]

Wrong assumption:
To remove the GC you don't need to drop the tranny pan.
You need to remove the tranny's electrical connections box at the firewall and remove the connector to the tranny.
Remove the three connections art the top of the round box part (the tranny's electrical connections), note how they are connected.
Pull the disconneted cable back towards the GC (don't forget to loosen the clip at the tranny).
Then remove kick-down cable from the GC and remove the GC from the gearbox.
Make sure the axle comes out with the GC.
Now you can take the complete wiring and GC from te car for servicing.

:)

I went to follow this plan tonight but ran into a couple of problems/questions.

The "three connections at the top of the round box part" (brown/green/blue) are easily disconnected and this thinner cable goes to a sensor on the drivers side of the tranny. I understand that part.

What about the other two larger cables. They seem to be permenantly connected to this "connections box", so to remove the GC, you must also remove this connections box, the two cables and the additional sensor on the passenger side of the tranny? Which means draining the transmission? Am I missing something?

I hadn't realized this and hadn't any fresh fluid handy, so I stopped and regrouped. After review, it may not be my GC after all. New thread time......

[Chris Burns]

Sounds very strange! Hopefully your transmission isn't slipping!!

[Jonathan]

...Did a transmission drain and fill a couple of weeks ago. Put in 4.5 qts, so the level is to the bottom of the spiral. Maybe a little full?

Yes, maybe a little full.

The advice I got on changing ATF was this:


Changing the fluid is easy, just pull the drain plug and let it out, then put the new stuff in through the dipstick tube. Put in two quarts, start the engine, then add the rest checking the level as you go. A drain/fill like that will take just under a (US) gallon to refill. You should change the drain plug seal, it is the same as the one on the engine oil pan.

The dipstick is hard to read as the ATF is very thin and clear. You definitely have to measure it with the engine warm and running, if the engine is off it will look way over full.

[Dangermouse]

I will suck out 1/2 a quart today, but not sure if it is related to this problem. Maybe 200 miles since fluid change.

[Ron]

First, it's not from being overfilled, but remove any extra to prevent other problems.

Chase where the power is coming from that allows the two lights to stay on when you pull the fuse and I bet you will find the problem -- pulling the fuse should kill the circuit and make them go out (they, and thus the shift solenoids, have power on them at all times the key is on and the governor grounds them to make them activate ie they are ground controlled). This is why, normally, if you want to know if it is in 2nd or 3rd, you can pull the fuse and if it shifts up, you were in 2nd.
(fyi- 3rd is supposedly "limp mode", but I think it is coincidental rather than by design because everyone else uses 2nd, if possible, as it VERY hard on the clutch packs when starting off from a standstill).


I'm trying to remember a 3rd harness wire there...I'll post up shortly....

[Dangermouse]

In the absence of any other suggestions, that was my plan of attack this afternoon. If the GC is OK, then I don't want to fool with it until I get whatever else is screwed up fixed, otherwise I'll be chasing my tail.

I have all the parts, so I may just set aside some time and do it anyway.


aside - anyone know what the two sensors on the transmission are called (and which is which)?

[Ron]

...Check out this pic (http://dmctalk.org/attachment.php?attachmentid=960&d=1307761414) in the Governor Computer Section. I only see and remember 2 harnesses from the black block connector...???
There is a Chart (http://dmctalk.org/attachment.php?attachmentid=953&d=1307760396)I made for it there too..


The one on the driver side is for the shift override/request, reverse lights, and start inhibit combo switch. The other, passenger side, is for the governor computer, of course.

I must not be with you...ya have more info or a pic of the 3rd one/"sensors"?

You are only a couple of hours away....your turn dude LMAO!!!

EDIT: Do NOT try to unscrew the outer two brass screws...the 3 in the middle go to the solenoids and the outer two are molded in solid!

[David T]

In the absence of any other suggestions, that was my plan of attack this afternoon. If the GC is OK, then I don't want to fool with it until I get whatever else is screwed up fixed, otherwise I'll be chasing my tail.

I have all the parts, so I may just set aside some time and do it anyway.


aside - anyone know what the two sensors on the transmission are called (and which is which)?

In this application the caps are hooked up to an AC voltage so polarity is irrelevant. If you still have both lights lit even after removing the fuse and you are not in 1st gear something is very wrong (you are probably pulling the wrong fuse). With both lights out (fuse pulled) you are (or at least should be) in 3rd. You should have a card with the RPM V road speed so you can tell what gear you are in. Be sure it is for the automatic. Checking the fluid level properly is important. There is a whole procedure in the Workshop Manual explaining how to do it. Always check the final drive level too.
David Teitelbaum

[Ron]

$.02

David, note the caps have a set of diodes (1N1202C) between them and their feed from the signal generator(s)......

========

Electrolytic caps may work OK, but they "belong" in things like power supplies -- Tantalum are much better for switching circuits.

[David T]

$.02

David, note the caps have a set of diodes (1N1202C) between them and their feed from the signal generator(s)......

========

Electrolytic caps may work OK, but they "belong" in things like power supplies -- Tantalum are much better for switching circuits.

Agreed, but electrolytics were plentiful and cheap "back in the day" and Tantalium, if it was even available, would have been way out of the price range (something you heard of but never saw and was put into satellites). As you can see they spared no expense when they designed and built the shift controller, aka shift computer, aka governor. That particular cap you opened has diodes, the ones I use don't (at least I don't think so, I never opened them!). Heck, they didn't even include spike suppression for the IC. Or reverse polarity protection or overload protection for the output transistors. Today with semi-conductors being so cheap, if the IC package didn't have internal protection any good designer would include it. As for using the electrolytics, you can't really blame age, these things were blowing up pretty early. Probably the voltage rating is too low. Again, because they cheaped out. Maybe they were all defective and overrated. In any case the wrong type of cap used in the wrong place.
David Teitelbaum

[Bitsyncmaster]

Both tantalum and electrolytic caps have a low impedance powered backwards. If the voltage is high enough it can also puncture the foil inside the cap. In an AC circuit you would normally use two caps back to back to back and a diode to prevent excesive voltage when reverse biased.

I fixed one AUTO unit and the caps were damaged but the real problem was a broken solder joint. It's hard to see broken joints because the boards are conformal coated. Broken joints are a big problem with circuit boards without plated through holes.

[David T]

Both tantalum and electrolytic caps have a low impedance powered backwards. If the voltage is high enough it can also puncture the foil inside the cap. In an AC circuit you would normally use two caps back to back to back and a diode to prevent excessive current when reverse biased.

I fixed one AUTO unit and the caps were damaged but the real problem was a broken solder joint. It's hard to see broken joints because the boards are conformal coated. Broken joints are a big problem with circuit boards without plated through holes.

Yes, on top of the lousy quality and bad design the workmanship was also poor. Cold solder joints that fail over time because of vibration and thermal stress. When you think about it, it is impressive they worked as well and as long as they do! That is one reason I always thought it was an area ripe for further development. A programmable controller would make a lot of sense. Of course from an economic point of view it makes no sense at all. Much easier, faster, and cheaper to just keep repairing the old clunker.
David Teitelbaum

[Dangermouse]

Chase where the power is coming from that allows the two lights to stay on when you pull the fuse and I bet you will find the problem -- pulling the fuse should kill the circuit and make them go out ....

OK, I was dillusional late last night when I posted. Sorry.

Checked again, without doing anything else, and pulling the fuse does cause the lights to go out. Don't know what I was thinking.

Checked that I have power all the way though to the two L shaped connectors on the connector box.

Replaced the small piece of cable that showed heat damage, only to find that it was just cosmetic.

Back to square 1.

Here's possibly something (or nothing) Car's back wheels are on ramps, with the hand brake on. Turn ignition to the notch before 'Start" (but didn't start engine), so the dash lights go on, and the LEDs in my light box both light, as noted earlier.

Put foot on foot brake and moved the selector from P to D, and lights stay on. Move back to P, lights stay on. Take my foot off the foot brake and the car settles a little on the parking brake, and the lights go off. Foot brake on and move back to D, lights stay off. Back to P and the back to D, and one light comes on. Turn key off and then on, and both lights come back on.

Haven't been able to replicate this, though.

[Dangermouse]

Where are the switches S1 and S2 located?

[Ron]

As you know, one light is for 2nd gear. You should never see one light when the wheels are not turning (not like some cars or mostly trucks where you can select 2nd and pull off in it)....sounds more and more like the governor to me.

S1 and S2 are what is in the unit mounted on the drivers side (it is sealed). You have to drop the pan to get it out. I have never heard of that part being bad. I have one from a core just in case, IIRC...been a while since I rebuilt any of them...J came out with his replacement and the vendors all started having them...

[Dangermouse]

I worked out where the switches were and was able to test the operation of them, except 1B as it doesn't pin-out through the connector. All look good.

So we are back to the GC then?

Actually, don't pay too much attention to the 'one LED" situation I noted above. I found one of my LED cable probes had a dodgy connector, which would take out 1 LED but not both.

[Ron]

I worked out where the switches were and was able to test the operation of them, except 1B as it doesn't pin-out through the connector. All look good.

So we are back to the GC then?
Sounds like it...

fwiw- IMHO, on a DeLorean, when the fluid has been in there a while and it's still fairly clear and pink, if the trans is acting flakey, it is usually the GC, especially when the test lights are not acting as expected... And that is usually because of shorted harness (burnt), bad solder joints, then blown caps.

[David T]

Sounds like it...

fwiw- IMHO, on a DeLorean, when the fluid has been in there a while and it's still fairly clear and pink, if the trans is acting flakey, it is usually the GC, especially when the test lights are not acting as expected... And that is usually because of shorted harness (burnt), bad solder joints, then blown caps.

The test light rig (aka light box) is really meant to be used while the car is moving and shifting, not stationary on ramps. Drive the car and see how it shifts and how the lights light up. Generally shifting problems (especially if erratic) are most often caused by a flakey shift computer. Most common symptom is delayed or back-and-forth shifting on the 2-3 upshift. Most noticeable once the car gets warmed up. A damaged wiring harness usually will present as a solid and repeatable problem.
David Teitelbaum

[DMCMW Dave]

The test light setup works fine on ramps. Another good test is to pull the whole CG off the trans and spin it up with an electric drill (ignition on, test lights connected). At zero RPM the lights should be on, as the drill speeds up you'll see them go out in turn. Not a very absolute test as you can't really meter the RPM where it changes, but at least you can see it work.


The two switches are mounted on the passenger side. One of those is the backup light switch and one is the neutral safety (start interlock) switch. I have never seen either switch fail.


The connection on the driver side is the two shift solenoids.

-------------

Nobody has mentioned it here, and I typically don't use the forum to tout our products, but the DMCH Computer Governor upgrade is really a superior product for this. It is not as cheap as fixing the one in your car, and not a DIY install at the board level.You send us your governor assembly and we replace the entire internal board set with a new modern microcontroller-based device on modern circuit boards. (Advance core exchange option is available too but I happen to prefer upgrading the same one you send in.) When finished it looks 100% original with no outboard boxes or cut up wiring.

Shift points are better (slightly higher) and much more consistent.

We've been installing them for several years now with ZERO failures.

[DMC5180]

Nobody has mentioned it here, and I typically don't use the forum to tout our products, but the DMCH Computer Governor upgrade is really a superior product for this. It is not as cheap as fixing the one in your car, and not a DIY install at the board level.You send us your governor assembly and we replace the entire internal board set with a new modern microcontroller-based device on modern circuit boards. (Advance core exchange option is available too but I happen to prefer upgrading the same one you send in.) When finished it looks 100% original with no outboard boxes or cut up wiring.

Shift points are better (slightly higher) and much more consistent.

We've been installing them for several years now with ZERO failures.

If I had an Automatic, which I don't, It would be the FIRST thing on my list to replace with the IMPROVED DMCH UNIT. (piece of mind has a comfort value)

[Ron]

The two switches are mounted on the passenger side. One of those is the backup light switch and one is the neutral safety (start interlock) switch. I have never seen either switch fail.


The connection on the driver side is the two shift solenoids.OOPS! Sorry Dermont! I guess you found out by now since you were soldering already.
My turn to be delusional...actually, my memory forgot I was laying under the car or was in Chevy/Ford mode..


Dave, I can't remember if it was you or James I discussed it with long ago on .com, but you do agree the switches do more than run the backup light and start interlock, correct? (Just checking!)
Not worth the trouble!



Nobody has mentioned it here, and I typically don't use the forum to tout our products, but the DMCH Computer Governor upgrade is really a superior product for this. It is not as cheap as fixing the one in your car, and not a DIY install at the board level.You send us your governor assembly and we replace the entire internal board set with a new modern microcontroller-based device on modern circuit boards. (Advance core exchange option is available too but I happen to prefer upgrading the same one you send in.) When finished it looks 100% original with no outboard boxes or cut up wiring.

Shift points are better (slightly higher) and much more consistent.

We've been installing them for several years now with ZERO failures.

Well, I kinda hinted at it being one of the reasons I quit repairing them....:devil:

[DMCMW Dave]

Dave, I can't remember if it was you or James I discussed it with long ago on .com, but you do agree the switches do more than run the backup light and start interlock, correct? (Just checking!)
:

Yeah but I don't recall what (or worry about it any more) either.

[David T]

Yeah but I don't recall what (or worry about it any more) either.

Checking my notes, the only switches are the switch in the case that is for the starter interlock (Park and Neutral) and the reverse light. The other switch is the kick-down switch by the throttle spool. There is other functionality in the shift computer but is not used in the Delorean. As for bench-testing the shift computer, you can measure the speed you spin it at with a drill and measure the shift points as the lights go on and off. The up-shift points are different than the down-shift points and vary depending on the position of the quadrant arm (which is measuring engine load by throttle position). When I repair a S/C I bench test it before and after to make sure it is working before going through all of the trouble of putting it back into the car. BTW the shift points are also affected by the hydraulic valve, the line pressure and the vacuum modulator. As for testing on ramps, you can't because you can't spin the wheels. On jackstands you can but if the car can be driven it is just as easy to drive it as long as you made the wire to the light box long enough so you can have it alongside you as you drive.
David Teitelbaum

[Ron]

Yeah but I don't recall what (or worry about it any more) either.


There is other functionality in the shift computer but is not used in the Delorean.
...
The up-shift points are different than the down-shift points and vary depending on the position of the quadrant arm (which is measuring engine load by throttle position).
...
BTW the shift points are also affected by the hydraulic valve, the line pressure and the vacuum modulator

The selector switches also affect the shift.
See:
Table- http://dmctalk.org/attachment.php?attachmentid=959&d=1307760816
Schematic (S1 & S2 lower left) -http://dmctalk.org/attachment.php?attachmentid=957&d=1307760737

[Dangermouse]

Update time:

I have had this damn GC off so many time today I could do it in my sleep :). Leaving the various plugs connected I am able to get the GC out from under the car and determinate the 8-wire connector there before bringing the boards into the air conditioned house.

Replaced the transistors with TIP42B and capacitors with 4.7uF and 10uF (35V) respectively. I must say that it is trickier than it looks as the traces are pretty fragile. First attempt was a bust as one of the transitors wasn't seated right, so when I put it back in the car, only one light came on. Out again and repairs, but this time the other light wouldn't light. WTF. Out again and redid the connections on the other transistors. Re-installed and the light was still out. Only then did I think about checking the LED, and what do you know, it was faulty. WTH.

Switched leads and it lit. Need to fix the lightbox tomorrow.

Checked the continuity of the wiring from the bulkhead to the black connector box. All OK

All wiring was inspected when it was out of teh car with no signs of damage (otehr than the above mentioned repair)

Checked the resistance of the solenoids. One was 28 ohms and the other 26 ohms, which seems twice what they should be based on the schmatic (12V, 10W). Can anyone confirm what they are/should be? (edit: just dawned on me that this includes the cable from teh connector box, and this is the cable with two butt connectors in each conductor which will probably affect the resistance)

I had been proceeding on the basis of Dave S's comment above about the light-check being OK while the car is on the ramps but after a PM that I need RPM to get the lights to change, I got all excited that it was fixed and drove it for a few hundred [yards]. Still no gear change, but I have no faith in what my one remaining LED was telling me (it was connected to Solenoid A, 1st gear - it was lit at the start and when the revs got to a certain point, it went out,and slowing down turned it on again, but no corresponding gear change. But then it went out and stayed out, so I don't know any more)

Assuming that a repaired light box will show me lights changing (on/off) but no corresponding gear chanes, am I going back inside the GC? I only replaced the components mentioned above (being the most likely candidates for a problem), as well as re-doing the connection points, but the majority of the other connections were left as-is. They all "looked" OK, or at least they all looked the same, undisturbed in 32 years.

If I need to "re-do" them, to what extent? Scrape off the coating and melt the existing solder, or remove all the existing solder, clean and resolder, with the inherent risk of FUBARing the trace. (yes, Dave S's option is certainly more attractive than doing all that, but at present this is my DD, so I would really like it to be mobile by tomorrow night)

Any suggestions or advice gladly taken.

[Bitsyncmaster]

If you find the bad solder joint, use some solder-wick to get the coating and solder removed. Then you have a clean pad to resolder the connection.

[Ron]

If you blew a LED you can use mini lamps.

You have to let the wheels spin before the lights will change...they show you when the solenoids are in fact receiving power to energized them, not what is requested or demanded by you (via the selector) or any other part in the system.
The lights are simply in parallel with their solenoid. So, to include your other question, if the lights work correctly but no shifts, it means that the solenoid(s) are bad (NOT likely), or, you have a bad connection to the solenoid(s).
EDIT: ...assuming there is nothing physically wrong with the valve body, clutches, etc...

FWIW- I'd guess you have a bad trace, solder joint, or maybe got one of the parts too hot when installing it (easy to do).

[David T]

If you blew a LED you can use mini lamps.

You have to let the wheels spin before the lights will change...they show you when the solenoids are in fact receiving power to energized them, not what is requested or demanded by you (via the selector) or any other part in the system.
The lights are simply in parallel with their solenoid. So, to include your other question, if the lights work correctly but no shifts, it means that the solenoid(s) are bad (NOT likely), or, you have a bad connection to the solenoid(s).
EDIT: ...assuming there is nothing physically wrong with the valve body, clutches, etc...

FWIW- I'd guess you have a bad trace, solder joint, or maybe got one of the parts too hot when installing it (easy to do).

I remember Dave S finding a car that didn't shift right, a blob of silicone was plugging up a shift solenoid. He found it when he removed the solenoids. My notes say 25 ohms, you are very close so that should rule out any wiring problem or a burnt solenoid. As Ron says the shift computer can only power the solenoids (or not) so if you have the lights working as they should and you still are not getting shifts the problem is internal to the transmission. Check the adjustment on the shift selector and make sure it is getting into the right spot on BOTH the gear selector AND the detents in the transmission. You do not need to get fancy with LED's, any small 12 volt bulb will do. Yes, you do have to trust your test equipment so it serves you well to check it before using it. As long as you are checking things you should do ALL of the external On-Car adjustments including a line pressure check.
David Teitelbaum

[Dangermouse]

I got all excited that it was fixed and drove it for a few hundred years. .

First of all, F’ing spell check.


Second of all, update and a final question, that I think I know the answer to.

Took the GC off again and scraped and re-soldered every damn connection on the boards.

Fixed my light box and connected a drill to the GC and it showed one light going out as the revs increase. (The second one never changed). Which is what I found when I drove it a few hundred YARDS earlier. Have only 50/50 confidence that the GC is operation and that I didn’t bugger anything up, so I elected to send it off to DMCMW and get the new microprocessor one. (followed that handy “How To (http://dmctalk.org/showthread.php?7648-How-To-Remove-the-Automatic-Transmission-Governor-Computer):” that someone posted recently – good job author ;) ).

Got it back (great turnaround guys) and fitted it on Saturday morning (no fun at all as it was done using jacks on the frame instead of ramps which really restricted access). Filled the tranny with fluid, and took it for that few hundred yard test run, confident that Dave had worked his long-distant magic on my problem, and no difference !!! First light turned off as the revs were a little higher, but no corresponding shift.

Feels like it is starting in 2nd , rather than 3rd, as it doesn’t seem overly stressed, or slipping too much, but pulling Fuse 13 does nothing.

So my assumption is as follows: my original GC was OK, I replaced components and re-soldered joints and it was still OK; replaced it with a tested unit from DMCMW and no change. (btw, I am certainly not complaining about Dave’s replacement part).

And my understanding of the system now is that the GC detects the speed, and calls for a solenoid to disengage, as it should, so it looks like the problem is (and probably always has been) in the tranny.

Are there any other checks I can do at this stage?


[Note on fluid level - when I took the GC off, I removed the drain plug and drained the transmission until fluid was just dripping out of the plug hole. I was just removing the switch connector, and not the solenoids, so I didn't remove the pan. I measured 4 qts of fluid came out. I replaced the drain plug and stuffed some paper towel in the connector opening.

A week later, when I went to refit the repaired unit, I originally planned on dropping the pan, so I thought I'd better drain whatever fluid was in there. I was surprised that a further quart came out. Is that normal? I am presuming that all the little amounts of fluid that coat the interior had just drained down to the pan, but at this stage I am looking at everything. ]

[DMCMW Dave]

A week later, when I went to refit the repaired unit, I originally planned on dropping the pan, so I thought I'd better drain whatever fluid was in there. I was surprised that a further quart came out. Is that normal? I am presuming that all the little amounts of fluid that coat the interior had just drained down to the pan, but at this stage I am looking at everything. ]

I find that if you drain the pan you'll get not quite a gallon out. If you leave it open over the weekend it will drip another quart, my assumption is that this is just the stuff coming off the clutches and out of the converter.

Check everything - I actually had one in here where for some insane reason somebody had reversed the solenoids. That was a pretty fun one to find. Also check the solenoids (you have to pull them out) for split O-rings where they go into the converter. I've seen that cause weird problems too.

You will note the service manual drawing that they show two different wire colors on the solenoids (actually clear and grey) - that is important and has to be correct.

For you binary thinkers, with two solenoids you could really run a 4- speed transmission:

Solenoids powered:
on - on (first gear)
on - off (second gear)
off - on (illegal)
off - off (third gear)

In the DeLorean case, the off-on case is an illegal condition and the transmission will not care for it at all. You can have this condition if the solenoids are physically reversed or the solenoid wiring is reversed at the junction box.

[David T]

I find that if you drain the pan you'll get not quite a gallon out. If you leave it open over the weekend it will drip another quart, my assumption is that this is just the stuff coming off the clutches and out of the converter.

Check everything - I actually had one in here where for some insane reason somebody had reversed the solenoids. That was a pretty fun one to find. Also check the solenoids (you have to pull them out) for split O-rings where they go into the converter. I've seen that cause weird problems too.

You will note the service manual drawing that they show two different wire colors on the solenoids (actually clear and grey) - that is important and has to be correct.

For you binary thinkers, with two solenoids you could really run a 4- speed transmission:

Solenoids powered:
on - on (first gear)
on - off (second gear)
off - on (illegal)
off - off (third gear)

In the DeLorean case, the off-on case is an illegal condition and the transmission will not care for it at all. You can have this condition if the solenoids are physically reversed or the solenoid wiring is reversed at the junction box.

Another weird thing I found once is the cable and the end thread into the transmission. It is possible to get the detent of the console so far off the detent of the transmission that you are "in between" gears. You have to make sure when you are in D3 on the gearshift the transmission valve body is fully in the correct detent too. That is why when you have transmission problems I advise to go over ALL of the external "On Car" adjustments.
David Teitelbaum

[Ron]

+1 Dave S

A lot of that fluid had to flow back through the filter...

Although I've never heard of one going bad, I'd check the multi-function switch first...
It is easy to do at the L shaped plugs using the Schematics in Resources (Post 1) (http://dmctalk.org/showthread.php?350-Automatic-Transmission-Governor).
Don't let the differences in the logic table I used and Dave's here bite you (arbitrary choice of solenoid A & B).

[Ron]

Another weird thing I found once is the cable and the end thread into the transmission. It is possible to get the detent of the console so far off the detent of the transmission that you are "in between" gears. You have to make sure when you are in D3 on the gearshift the transmission valve body is fully in the correct detent too. That is why when you have transmission problems I advise to go over ALL of the external "On Car" adjustments.
David Teitelbaum
+1

Back when, I was doing some cleaning and somehow got the cable out of its track. It didn't like it at all!
:slap:

[Dangermouse]

Another weird thing I found once is the cable and the end thread into the transmission. It is possible to get the detent of the console so far off the detent of the transmission that you are "in between" gears. You have to make sure when you are in D3 on the gearshift the transmission valve body is fully in the correct detent too. That is why when you have transmission problems I advise to go over ALL of the external "On Car" adjustments.
David Teitelbaum

Thanks, I'll try that. I presume you remove the pan and check the valve body that way. Are the detents marked?


+1 Dave S

A lot of that fluid had to flow back through the filter...

Although I've never heard of one going bad, I'd check the multi-function switch first...
It is easy to do at the L shaped plugs using the Schematics in Resources (Post 1) (http://dmctalk.org/showthread.php?350-Automatic-Transmission-Governor).
Don't let the differences in the logic table I used and Dave's here bite you (arbitrary choice of solenoid A & B).

I tested those switches earlier, via continuity and the L shaped plugs, and they checked out OK



I find that if you drain the pan you'll get not quite a gallon out. If you leave it open over the weekend it will drip another quart, my assumption is that this is just the stuff coming off the clutches and out of the converter.

Check everything - I actually had one in here where for some insane reason somebody had reversed the solenoids. That was a pretty fun one to find. Also check the solenoids (you have to pull them out) for split O-rings where they go into the converter. I've seen that cause weird problems too.

You will note the service manual drawing that they show two different wire colors on the solenoids (actually clear and grey) - that is important and has to be correct.
.

I intend to double check those wire colors again as I put a splice in. Even though I have been over it about 3 times.

Can anyone confirm which goes where on the connection box (green/yellow goes to the center and I have brown on the one closest to the front of the car, blue being at the back one).

[Ron]

Can anyone confirm which goes where on the connection box (green/yellow goes to the center and I have brown on the one closest to the front of the car, blue being at the back one).
The box can sit two ways...
Two Ds here have: (Clockwise) Gap, Stud, Blue, Yellow, Brown, Stud.
(I don't see Green on the Yellow one, but it could easily be on the underside.)

[Dangermouse]

Thanks,

that's what mine is.

Yes, the conductor is green/yellow. Equal width green and yellow, rather than a tracer. That 3 conductor cable is used as domestic appliance cable for 240Vac fridges, kettles etc in the UK, where the green/yellow is ground (earth), brown being the hot and blue being the neutral. Another exotic part of our car, eh?