Maybe a stupid question, but is trhere a way to manually "switch" the converter into full lockup on the 4R70W? In some 80's GM transmissions, one could simply jumper two pins on the diagnotic port and lock the TC. I'm thinking that this might be beneficial when towing in OD. (Then again, I might be crazy.)

Andy

 

There is for the 4R100. Common for guys use it to lock second gear for sled pullin. I'll look up how to do it so you can give a try on your 70.

Adrianspeeder

 

Excellent! Thanks! I'll look forward to that.

I checked out in my manual in the mean time, and it looks like there's a violet/yellow wire from the PCM that controls the lockup. I imagine I'll need to find that for my connection. Think I might use a latching relay ckt that will auto-disengage when I hit the brakes. Whaddaya think?

Andy

 

Anybody had a chance to play with this idea, or am I gonna be the guinea pig?

Andy

 

Thought I'd pop this TTT.

Andy

 

Doh! Sorry bud, forgot to look for ya. This is for a 4R100.

http://www.forgotton.net/mods/tclock/index.htm

Adrianspeeder

 

Thanks, Adrianspeeder!

Wonder if I could put a relay in line such that the manual lockup will not work in 1st gear? I'm not going to be pulling 8,000# with this thing any time soon, and that would allow me to leave the switch in "lock" mode without worrying about getting to slow in 1st. My main concern is being able to lock up and stay locked in OD, as this seems to be my only "problem" area right now.

Ideas?

Andy

 

I would suspect that if you override the PCM's control of the lockup circuit, that the PCM will likely complain about it and set a DTC for the TC ratio out of parameters.

Depending on the PCM's programming there could either be no ill effects or the PCM might be thrown into a "limp" mode.

Just something to keep a eye out for in case you decide to go the guinea pig route.

Steve

 

It does set the check engine light on the diesels, but no operational problems. Sorry, I just havent fooled around researchin it as I haven't found a need.

Adrianspeeder

 

Lockup in first gear is not physically possible inside any of the aode variant transmissions. The valve blocks it. A proper tune is the best thing a switch allows for operator error and can be destructive. Remember the OEM converters are designed to modulate, they don't hold 100%.
Alan

 

Funny. I was looking back at old threads and saw your reply, Alan. Didn't see it before. I was still considering this mod, and am now curious about your statement. Can you expound on it a bit?

What can go wrong if the T/C is electronically locked up via manual switch?

Other than when stopping or in situations needing high torque (hard acceleration or starting out from a stop), when should the T/C not be locked? BTW, I was considering a brake-switch interrupt for the circuit, so that any time the brakes were applied, the trans would revert to PCM control.

I understand the T/C modulates due to variations in load, but that's what I'm trying to avoid under certain circumstances. I would like to eliminate "gear #3.5" when the T/C unlocks in OD before down-shifting. I prefer it to simply down-shift, instead. My thought is if the T/C is locked at this point, the PCM will see the increased load and shift. Maybe a tune is the "right way" to accomplish this, but that would be big $$. (Of course a trans repair would be expensive, as well, I suppose.)

Trying to understand these things better, and will appreciate your elaboration. Thanks.

Andy

P.S. This isn't a huge deal, especially given the few times a year that I tow the T/T. I now simply watch the tach and/or listen for the increased revs, then tap the O/D button. It would just be nice not to have to stay focused on that when there are so many other things to watch out for while driving.

 

Unlocking for the shift was done to protect the transmission. People have locked the tcc solenoid through a switch before but it was not meant for constant power. You'll find if you do this you will be replacing the solenoid often. No matter what you do in the end it will cost big $$.
Alan