Transmission forgets to down shift

[Magnus86]

Hey guys,

after a long time another post from me.
I had some issues with my automatic transmission with a lots of erratic shifting, not starting in first gear etc.
To fix this issue i removed the governor computer, replaced the two blown capacitors and resoldered a few of the solder joints (not all).
After that, there is no more erratic shifting like unexpected down- or upshifts, no slipping gears etc., already way better than before.

Unfortunately it seems like i still have some problems with the transmission.
When the car is cold it starts from the first gear and shifts as expected into 2nd and 3rd but then sometimes seems to forget to downshift again at the expected shifting points. That causes sometimes that i'm stopping on a red light and the car doesn't start in first gear when i want to continue driving. Instead it starts in 2nd or 3rd gear. When this happens, even the kickdown doesn't work. I can get it manually into first gear when i set the shift lever to 1 and do this when this problem occurs so that i don't burn the clutch pads. This behavior stays for around 3-4 minutes of driving until the problem stops and everything works as expected. After those 3-4 minutes of driving, i get nice up and downshifts without any problems.

Any idea what could cause this behaviour?
It seems like something needs to warm up first.
As i said i didn't resolder all solder joints of the circuit board. Of course i resoldered those of the new capacitors, the solder joints of the red wire that connects both circuit boards and a few other solder joints.
Should i have resoldered all solder joints or is there anything else that can cause the problem i described?

Almost forgot, what i also did:
- Transmission fluid level should be good. When engine is hot and running, the dipstick shows "hot" while the shift lever is set to "park"
- I also cleaned the contacts on the governor computer plugs, especially those three wires in the round plugs were a bit corroded
- I haven't checked the fuses yet, but when i got the car a few months ago, i replaced all the fuses with new ones

[David T]

I would suspect you still have some "cold" solder joints that need to be "reflowed". The factory did a lousy job soldering those boards. With time and vibration they often fail. When you have problems with the OEM shift computer, especially if they come and go, the first thing you should check is ALL of the solder joints.

[glowof1000suns]

You?re not alone! I?m having the same exact issue. I?m interested to know if fresh solder fixes it. Good luck?to both of us!

[Ron]

You could make up some Test Lights (https://dmctalk.org/showthread.php?350-Automatic-Transmission-Governor&p=26804&viewfull=1#post26804) to eliminate the governor computer...
But it does sound like bad solder joint(s).

[Magnus86]

Thanks for your replies.
I guess the first thing i?ll do (and the easiest one) is to hook up those test lights. As far as i can see i have to get the +12V from the C-Connection of the plug for the lights and then the ground for one light goes to B and the other one to D, right?
Which of the connections (B and D) belongs to which solenoid?🤔

@David:
I checked all the Solder Joints visually and they all looked good to me. I couldn?t see any suspicious solder joints (see attached pictures). So you recommend resolder all joints anyway? Then i have to get the governor out again when the light test will fail right? I didn?t want to resolder all of them because they looked good and it?s quite hard to get this nasty protection film off. One thing i noticed:
When i reinstalled the governors switch-thing and screwed it in place, at some point i could hear a loud ?click? noise. First i thought i broke something and removed that switch..but everything looked good. After reinstalling it again i got the same clicking noise at some point while screwing it in place. Is that normal?

Thanks a lot!

69600
6960169601

[mhanch]

I had exactly this behavior, and the cause for me was that both of the Throttle Microswitches were stuck. Unplug them and see if it gets better. you can also use a small screwdriver to push and verify that they open/close properly.

I cleaned mine with WD-40 and cycled them a few times and it all came back to normal.

[Ron]

Thanks for your replies.
I guess the first thing i?ll do (and the easiest one) is to hook up those test lights. As far as i can see i have to get the +12V from the C-Connection of the plug for the lights and then the ground for one light goes to B and the other one to D, right?
Which of the connections (B and D) belongs to which solenoid?
Yes, both bulbs will be fed 12V, waiting on the GC to ground the other side...
69602

[glowof1000suns]

I had exactly this behavior, and the cause for me was that both of the Throttle Microswitches were stuck. Unplug them and see if it gets better. you can also use a small screwdriver to push and verify that they open/close properly.

I cleaned mine with WD-40 and cycled them a few times and it all came back to normal.

I'm familiar with the microswitch located at the throttle spool. Where's the other one you mentioned? I see one listed in the parts diagram at the transmission, but it's unclear of where it's actually mounted.

[AugustneverEnds]

It's definitely worth checking the governor's circuit board again. Since you state that your transmission is having trouble downshifting you should check the kick down cable. The end might have popped out of the throttle spool or the quadrant arm on the governor.

[jangell]

Just to clarify: you mean the throttle cable that runs to the transmission is for to kicking the transmission down as you go slower? Not to be confused with the kick-down switch, which is for drooping to a lower gear for passing on the highway during WOT?

-- Joe

[Ron]

I'd be surprised if it were a cable, since it doesn't down shift at a stop sometimes by itself, but it will manually.

[AugustneverEnds]

Just to clarify: you mean the throttle cable that runs to the transmission is for to kicking the transmission down as you go slower? Not to be confused with the kick-down switch, which is for drooping to a lower gear for passing on the highway during WOT?

-- Joe

Yep, #10 here: https://store.delorean.com/parts/automatic-transmission/4-5-6-computer-modulator.html

Mine was disconnected once and the gearbox did some very scary stuff.

[David T]

Yep, #10 here: https://store.delorean.com/parts/automatic-transmission/4-5-6-computer-modulator.html

Mine was disconnected once and the gearbox did some very scary stuff.

Not likely it's the cable if the problem comes and goes. But it won't hurt to make sure it is properly adjusted. It does affect the shift points. As for switches, there is the multi-switch in the transmission for the reverse light and starter interlock, and there are three on the throttle linkage. One for the idle motor, one for the lambda override, and one for the kick-down. The 5-speeds only have 2 (they don't have a kick-down).