My 85 has had TC lockup quirks for a while now. I have seen other people post these same symptoms and now I am wondering how many others have had this happen. If so, would you respond with your remedy if solved.

Symptom: TC unlocks whenever I release (fully close) the throttle at speeds above about 35 mph. Then, as soon as I slightly open the throttle again, the TC locks up after about a second of rpm increase. I put an LED on the ALDL pins, and you can see the TC unlocking and relocking again. This started after putting a 2600 stall TC in the car. This is my second 2600 stall TC, and they both did the same. I really don't want to put a TC lockup manual switch in the car. Knowing that the ECM uses the TPS as part of its decision logic, I made sure that the TPS was properly adjusted. I really don't understand why it is important for the ECM to unlock the TC at highway speeds even if the throttle is closed. I would think it would help in engine braking if the TC was locked. Then when you got down to less than say 25-30, it could unlock to allow the engine to unload.

 

I am one of those people, but I have not yet solved my problem. If you hit the brakes and hold it when you go to hit the gas again, your TC unlocks. I do that usually until I can find the solution. I was told it could be a lot of different things, the TC itself, try to reset the computer and clear it, maybe it could be fuel related, flush the trans, etc. I would really like to know what the solution is, I hate this problem, I hate it when my car jerks a little bit when I hit the gas again. How hard is it to install a TC? I heard 7 hours! I will be doing this on my back also in my garage which will make it a lot harder! Any specific tools that I will need and that will help me install it easier, quicker, and successfully? Thanks, and if anyone knows a solution to our TC lock up problems, please help! Its driving me crazy! :crazy: :mad

 

If you're seeing the lock/unlock signal at the ALDL then it's purely an ECM issue as that's the command signal to the TC.

My '88 stays locked if I get off the throttle; it will unlock when I tap the brake or a hard downshift of course. Perhaps your '85 uses a different algorithm.

BTW I have noticed that the lockup doesn't happen till it's warmed up a little, so there may be a coolant temp factor in there too.

 

My 85 does the same thing ( always has ) with the original TC and the GM replacement I had put in with the rebuild. I have been told by a couple of trany guys that is the way it's supposed to be.

Rich

 

If this is normal, I hate it. The one second spin-up to lock is beaucoup annoying.

 

Go for the toggle switch. Mine works great and I leave it off for city driving.

 

I know this may be a trivial question but what exactly is TC lockup? I've been having some funny symptoms with mine lately and wondered this.

Regards,

Eric

 

Our A4s have a lockup clutch in the Torque Converter (TC) that is controlled by the ECM.

During light throttle and steady driving (never in 1st gear) this clutch is locked so there is no slippage in the TC. During acceleration and when you tap the brake pedle the ECM unlocks this clutch to allow normal TC slippage.

This term/function is not to be confused with TC stall/flash point, which is a characteristic designed into the TC and not thereafter controllable.

 

Is there any damage that can happen by running the converter locked all the time? And what if it is left locked around town, like if someone forgot to unlock it?

 

The TCC will lock up when the coolant gets to aboy 124-127...... then when it gets to any gear other than first and light throttle it will lock up. The brake pedal sensor will unlock it. It will lock up even if you manually shift the car. I have made a change to mine that only enables TCC in OVERDRIVE. I used a normally OPEN switch in the valve body that senses OVERDRIVE. Then I rewired the TCC to put that switch in series to the TCC. This way no matter what the computer says to the TCC it won't lock up 'till the trans conditions are correct .............in other words ...... in OD. :seeya

 

I've got a 91 with practically the same symptoms.

Mine seems to lock the converter way to quickly.
It'll lock at 22 mph if I'm accelerating gently.
Once locked it doesn't want to unlock. Depressing the brake WILL unlock it.

So... If I want to accelerate, I have to apply the brakes first.
This is driving me ba-zonkers trying to find the problem.
It's definitely not correct. It didn't do this when I first got it.

Mine likes to run through the gears quickly and lock the converter way too soon.
The result is the engine can't rev enough to make power and the thing falls flat on it's face.
I've got a 2700 RPM stall converter, also.

There is a temp switch in that keeps the converter from locking at all until the tranny temp reaches a certain temperature.

My Vette runs GREAT during the time the TC can't lockup.

Mine doesn't want to UNLOCK with a quick and moderate application of throttle. It SHOULD unlock so the engine can rev and pull.

It unlocks EVERY time with brake application. This is normal.
I think the TCC line is routed in series with one side of the brake pedal switch so this effectively unlocks it with brake application.
I believe this is to improve mileage.

I've replaced the ECM three times. Replaced the MEMCAL twice with used ones.
Ordered one NEW MEMCAL with the latest revisions and installed it.
Still no joy on the TCC action.

I have monitored the TCC line with my AutoXray and can see it command lock and unlock at various times.

In desperation, I put one of those "trick" TCC harnesses in the electrical cable to my transmission.

Now, the TC doesn't lock up at all. Sure DRIVES better, though.
Go figure.
I hope someone finds the answer to this.

 

Bowling Green, We have a problem! :(

 

Can I ask you how you managed to put a switch in the valve body that detects OVERDRIVE?
I have your old problem that it turns off as soon as I put the gear in from a standstill with a temperature of 120F. thanks