OD Lock up question

[Sgt Hollywood]

Okay, so I've been searching and reading all over the interweb to diagnose the issue I'm running into.

87' SWB - 350tbi - 700R4 - 3.08

So, here's the issue, when I gently (low RPMs easy on the pedal) drive, it appears that the TC is locking up in 2nd (mostly) and 3rd. Locks up then disengages. This doesn't happen all the time however.

Like its hunting.

It actually happens in Drive and OD. If I go a bit harder with the gas it doesn't seem to happen, but that could just because the TCC isn't getting the signal.

Unplug the TCC and its gone. Runs and shifts fine, just no Lock Up.

TV cable is adjusted correctly. Fluids all check out, I had installed a new TCC about 2 years ago. My speedo does fluctuate a bit sometimes maybe 1 to 2 mph. so maybe the VSS is getting a funky signal.

Maybe the Replacement TCC is failing?

I am temped to just put a toggle on the TCC since I really only want 4th OD for highways.


Any Ideas?

Thanks.

[eray92]

I have a toggle on my 200-4r and I can lock it in any gear. It works well. The toggle is on the ground wire just make sure your double action brake pedal is working.
Posted via Mobile Device

[Katrina/10]

Do you have a laptop you can connect to your ALDL?

[TheApocalyptican]

You say it disengages. You also said it's like it's hunting. Does this mean it's engaging and disengaging almost constantly, or is it just every once in a while disengaging, then reengages and is fine again for a while? I had a problem with my 700r4 that it would constantly engage and disengage. I tried the switch method, but it was a pain, plus the stock way locks it up more, and will keep them temp lower more of the time. My actual problem was with the tcc switch in the trans. Once I replaced it, it locks up correctly. However, due to the problem I was having (at least I am pretty sure it's related), I now have a converter with a broken stator, that freewheels when it shouldn't.

[beamn7]

I would certainly address the speedo issue while you are at it since the ECM takes that into consideration when locking up the TCC. You may want to check the TPS as well since that is also an input that is considered into the logic. Low rpm's around town and a slight increase on the pedal will command the TCC to unlock and then it will usually lock back up shortly after that. I personally don't care for that. Being that the TCC is a face appplied clutch inside the torque converter, every time it applies, pressure is being put on the thrust bearing and I have replaced a fair share of them especially on mid 80s vehicles. Having said that, I wired up a relay with a plug on each end so that it simply plugged in-line at the trans and converted mine to 4th only lock-up yet still supplied the feedback to the ecm letting it know it was locked. (ecm reduces the egr flow when the tcc is locked to avoid detonation) 700's must have the converter locked in 4th or it will overheat. Doesn't effect them in 1,2 or 3 but 4th, yes.

[Sgt Hollywood]

Originally Posted by TheApocalyptican

You say it disengages. You also said it's like it's hunting. Does this mean it's engaging and disengaging almost constantly, or is it just every once in a while disengaging,

Yeah, so say I'm just rolling out easy, shifts into 2nd properly, then TC locks up, and then disengages, all within 10 seconds or so, sometimes repeating sometimes not.

However the fact I am getting this while in "D" is peculiar.

I'll be dropping the pan and checking the solenoid and prob swapping in a new one in case, not the finest quality parts these days. I also just ordered up a 4th lock up only relay. so least that will lessen the annoyance in the future.

TPS was recently replaced when I had a TPS / O2 error codes, but could check the resistance.

As for the speedo, cables look good, connections solid, I guess I can test from the furthest point back to determine which side has the play.

Thanks for the input!

And yes to laptop, no to usb to ALDL connector. maybe time to dig out an old USB and some micro spade connectors