luke4907

iTrader: (5)

I've got a 700r4 that's not locking up at all. never used to in my old transmission with old torque converter, and it doesn't now with my new transmission and new torque converter. I finally got around to monitoring the voltages of the 3 wires at the TCC connector, and all of them provided anywhere from 13.5-14.4 when the vehicle was running when grounding to the F connector of the ALDL. There was one wire which actually went to 0.0v when I was driving the car at 40mph steadily, so I assume that's what's supposed to cause the converter to lock. Before I installed the tranny, I made sure the connections were good by removing the pan and checking the wires to the solenoid or whatever it is inside the transmission. Does anyone have an idea why my torque converter doesn't lock up?

luke4907

iTrader: (5)

anyone? this one is really starting to get to me...

five7kid

iTrader: (14)

I found out I didn't actually have 12 volts going to the tranny, although I didn't monitor at the ALDL like you did.

The TCC is locked by the ECM grounding the solenoid. Power to the solenoid, however, has to pass through the brake light switch. When you had the pan off, did you check for voltage at the solenoid with the ignition switch on? There's a 4-3 pressure switch on the valve body that's part of the circuit, too.

So, you need power at the solenoid in the transmission, and the circuit needs to be grounded by the ECM. Anything isn't right in that path, and it don't happen.

3rdGenBlackBird

The one that drops to zero should be the feedback reading, meaning that the solenoid is supposed to be energized.

Since you already checked the wiring before, I'd say the next step is to test the solenoid itself.

When you say "new" trans, do you mean rebuilt? One from another car?

Scott

luke4907

iTrader: (5)

I never had the pan off while the tranny was in the car, so I never got to check for voltage at the solenoid itself, although the wiring all appeared to be good and hooked up when I had the pan pulled off before I installed the tranny. I suppose I just might have to check that...

I just want to doublecheck: are all the wires on the TCC connector supposed to have 12v (except for the one that drops to 0v when the tranny is supposed to lockup) or maybe something is screwed up there?

If I'm able to monitor the voltage from the ALDL between pins A and F (and therefore see it drop to 0v when it should be locked, and therefore "ground" the circuit via the ECM), would that mean I have a bad TCC solenoid or the torque converter's lockup isn't working? I really have no idea about transmission internals and how it is supposed to not slip just by an electrical connection which doesn't have any wires going to the torque converter itself. I suppose I have some reading to do in that case...

luke4907

iTrader: (5)

Right, so when the one drops to zero, that "should" complete the circuit to the ground, correct? If the one wire goes to zero, does that mean any of the other wires should also drop to zero?

Yes the tranny was rebuilt, and I pulled it from my friend's car since he maybe put 500 miles on it. I never rode in his car to tell if the tranny was locking up, unfortunately, and he probably never even took notice. Only questionable thing is the tranny did sit for sometime (full with fluid), but works great other than this issue, and my previous tranny wasn't locking up either. I suppose the solenoids could be FUBARed on both trannies?

five7kid

iTrader: (14)

Two wires have 12v going to them. One is the TCC lock power, the other is the 4th gear indicator.

The return will also have 12v when the ECM is not commanding lock-up. When commanded, it should drop to zero since it will be at the same potential as ground.

The 4th gear is a high impedance/low current 12v signal. When the tranny shifts to 4th gear, the normally-open single-pole switch closes to ground, which the ECM sees and knows the tranny is now in 4th gear.

Since 2 difference transmissions acted the same way, that isn't indicative of a transmission-located problem.

luke4907

iTrader: (5)

What you stated here is what I have noticed. I did not check to make sure the 4th gear circuit is operating properly since I had the tcc connector disconnected from the transmission when I was testing out these voltage readings. I know it stayed 12v (although it was a lower reading than the other 2 lines, is this because of the high impedance/low current?) the whole time since I didn't have the connector plugged in so that the normally-open single-pole switch could ground the circuit.

So both the transmissions and torque converters not locking up isn't indicative of a transmission-located problem, and as far as I can tell the wiring is operating properly (correct me if I'm wrong please). Is there anything else I should check for? and thanks for the help it is greatly appreciated