Auto transmission: Slipping when accelerating + shifting too soon

[Henrik]

I have had my engine and (auto) tranny out of the car for a while and after I had put it back together and started driving it I noticed two issues:
a) There is some slippage (while in first gear) when I accelerate hard from a stop. I guess my first check would be the filter in the auto transmission. Is the transmission oil filter accessible once you drop the pan? What is the part number? I don't see it in the exploded views in the parts manuals.
and
b) It shifts too early. Is there a way to adjust the shifting points?

I did not open up the transmission when I had the engine out but I did separate it and the torque converter from the engine. The transmission fluid level is good and clear.

[Chris Burns]

Your transmission governor could be bad as well.

[Iznodmad]

I can't answer all your questions, but it is my understanding the filter is not able to be replaced with a new one (unavailable part). You must remove it and clean it then re-install. Hopefully those with more knowledge will chime in soon.

[DMCMW Dave]

I have had my engine and (auto) tranny out of the car for a while ---I did not open up the transmission when I had the engine out but I did separate it and the torque converter from the engine. The transmission fluid level is good and clear.

And it was OK before? Look for something you did wrong before taking things apart.

Check the kickdown linkage (if disconnected it will shift VERY early). Low fluid will cause slippage, this trans is pretty picky about that.

The filter is in the pan. Generally you just clean it. There is a gasket. The filter is hard to come by and expensive. #33 on this page:

http://store.delorean.com/c-292-4-5-3-valve-bodyinternal-linkage.aspx

[Ron]

Check your governor harness for signs of exhaust burns, being cut, or pinched...

From a dead stop, does it slip when the selector is in 1st AND when in Drive? Reverse?
Does it slip when shifting, or any other time?
ANY other symptoms?

Did you happen to clean the trans while it was out and possibly remove/disturb the below?
7591

[David T]

Is there any debris in the pan? To clean the filter you must cut it apart. You cannot even inspect it unless you disassemble it, you cannot see inside to see how much junk is there. Before doing anything, do the following:
Check the level as per the Workshop manual on level ground
Do ALL external adjustments
Check the line pressure
Do not drive on a slipping transmission. You will destroy the internal clutches, they are not meant to slip much and will quickly wear out. If the line pressure is low and cleaning the filter does not improve it your only option left is to have the transmission rebuilt. The shift computer does not make the trans slip, it only decides when and what gear to shift the trans into. The only way to change the shift points is to adjust the cable from the throttle to the shift computer. If it still doesn't shift correctly then you have a problem with the shift computer. There is a procedure somewhere (probably in the archive) on how to open the filter, clean it, and reassemble it.
David Teitelbaum

[SIMid]

Low fluid will cause slippage, this trans is pretty picky about that.


+1

I discovered this with mine. Leaks a little, but enough over a period of time. Usually slips between third and forth. Most noticeable when climbing hills. Topping up resolves the slipping.

[nofear365]

Third to forth, huh? :tongue:

[Dangermouse]

Third to forth, huh? :tongue:

Overdrive option :wink:

j/k.

[Henrik]

Check your governor harness for signs of exhaust burns, being cut, or pinched...

From a dead stop, does it slip when the selector is in 1st AND when in Drive? Reverse?
Does it slip when shifting, or any other time?
ANY other symptoms?

Did you happen to clean the trans while it was out and possibly remove/disturb the below?
7591

I know for sure that it slips momentarily with the shifter in D but the actual gear is in first. I will check with the shifter locked in first, second and reverse as well and get back to you.

It is possible that the vacuum modulator has been accidentally adjusted - I will look into it. How do I check it?

[Henrik]

Is there any debris in the pan? To clean the filter you must cut it apart. You cannot even inspect it unless you disassemble it, you cannot see inside to see how much junk is there. Before doing anything, do the following:
Check the level as per the Workshop manual on level ground
Do ALL external adjustments
Check the line pressure
Do not drive on a slipping transmission. You will destroy the internal clutches, they are not meant to slip much and will quickly wear out. If the line pressure is low and cleaning the filter does not improve it your only option left is to have the transmission rebuilt. The shift computer does not make the trans slip, it only decides when and what gear to shift the trans into. The only way to change the shift points is to adjust the cable from the throttle to the shift computer. If it still doesn't shift correctly then you have a problem with the shift computer. There is a procedure somewhere (probably in the archive) on how to open the filter, clean it, and reassemble it.
David Teitelbaum

How do I check line pressure? What is the correct pressure?

[Ron]

+1 David T


I know for sure that it slips momentarily with the shifter in D but the actual gear is in first. I will check with the shifter locked in first, second and reverse as well and get back to you.

It is possible that the vacuum modulator has been accidentally adjusted - I will look into it. How do I check it?


How do I check line pressure? What is the correct pressure?
All the same thing...covered in the workshop manual G:05:03 (there is a copy in the resource section here).
Again, do yourself a favor -- PARK YOUR D and read through the entire section! Then do the tests and adjustments/checks in this thread.

[SIMid]

Overdrive option :wink:

j/k.

*LMAO* I didn't realise I had typed it! :tongue:

Shows how good my maths are.

[Henrik]

Well, both of my problems have been resolved. The car upshifts and downshifts beautifully and there is no slippage whatsoever. The fix? I fell stupid admitting it: I had checked the transmission oil level with the engine off. After I had read the auto transmission section of my Workshop manual last night I realized that the engine needs to run when you check the oil level. It makes a huge difference! Engine off showed plenty of oil on the dip stick, engine on showed gave me a dry dip-stick! :yesss:

My excuse.... well, having grown up around stick-shifts and motorcycles I have no experience with auto trannys. Sure, the family cars are all automatics but - heck - those are checked by my local Jiffy Lube....

Thank you all for your input:thankyou:

[opethmike]

Thumbs up for an easy fix! Now to figure out why the fluid leaked out.....

[Henrik]

Thumbs up for an easy fix! Now to figure out why the fluid leaked out.....

There never was a leak. The reason it was low was that when I had the engine + tranny out I had drained the transmission oil so I could fix the seal where the dip stick goes into the transmission. So all is well.

[SIMid]

It's amazing how a small loss of fluid can make the gearbox slip.

I need to get my leak sorted soon.

[DMCMW Dave]

It's amazing how a small loss of fluid can make the gearbox slip.
.

"Off the stick" > small

[David T]

If you had the tranny out you lost all of the fluid that would have been in the cooler and the hoses. More than "just a little". Now check the final drive. I repeat, go over all of the external "On Car" adjustments since you had the tranny out. It still won't hurt to check the line pressure if for no other reason than to set a baseline. Recheck the fluid level often for a while to make sure it is right. Not only do you check the level you also check the condition of the fluid. It should be reddish transparent and not smell burnt. If you put it between your fingers it should not feel gritty. Make sure the vacuum modulator is hooked up and the vacuum hoses are not leaking, cracked, etc.
David Teitelbaum