What causes a tranny to not lock up?

[OneLethal87GN]

The tranny worked fine before the fateful day I raced it. It locked up when it should and everything. During the race the second gear band burnt up badly and warped the drum. After the "experts" at Aamco rebuilt my tranny it would not lock up. They said they replaced the lock-up switch and installed a lock-up convertor. They said they put the car on some kind of "box" that tells if the tranny is locking up or not and they said it is. They told me something in the wiring must have messed up. I've tried the brake test and also have the manual lock-up switch installed on my car and neither will make it lock up. What outside the tranny could keep it from locking up? I believe the Aamco people are liars about the little "box" gadget but can't prove it. I think they installed a non-lock convertor. I will eventually have a totally new tranny installed with a high stall convertor but wanted suggestions on what to look for in the time being. What wires should I test? Thanks for your time.

 

[DavzGN]

The little box was probably some type of scan tool that indicates that the ECM is commanding TC lockup. Either a bad electrical connection or a out of adjustment brake switch will prevent the TC from locking up when the ECM commands it.

HTH
David

 

[2quiktocare]

If their "black box" shows it locking it proves the electrical is working and it is a physical problem. It could be as simple as someone not putting the o'ring on the input shaft, but that would not allow it to lock up even on a black box test. You could be looking at a bad brake switch or a bad signal from the computer for the lock up as well. Why is Aamco not not willing to get into it to find the problem? And more so, why would you have Aamco to do your trans to start with? Their lack of customer service has been well documented on this board for years.

 

[OneLethal87GN]

Why is Aamco not not willing to get into it to find the problem? And more so, why would you have Aamco to do your trans to start with? Their lack of customer service has been well documented on this board for years.

If you do a search you'll find many of my old posts discussing the long ordeal in detail. I had them do the tranny in my 85 GN back in the mid 90s and they did a good job. This, along with a 3 year warranty, made me go back. Believe me I have spread the word about these guys. It's not just that location either. My next rebuild will be by someone on this board. How do I check the brake switch? Wouldn't it still lock up with a bad switch if I had the manual O/D lock-up switch installed?

 

[WE4]

One lethal...

Give me a call at the shop and we will go over a "flow chart" to try to diagnois.
It will take a few minutes and have a pen and paper to take notes. We WILL WIN!!! We will figure this out.!
Bruce
WE4
www.PTSXTREME.com
916-739-0510

 

[OneLethal87GN]

I'll try to give you a call soon. I need to also talk with you about a possible pressure problem. The car will catch 2nd under about 1/4 throttle but anything over that just causes a soft shifting of gears. This especially happens under any amount of boost. There doesn't seem to be slippage, just softness. The tranny has the bigger Alto band, your shift kit and a 200 servo so a hard shift should occur every time I would think. Thanks for the help you've given me in the past too Bruce.