4R70W trans ?????

[kstones63]

The 4r70w trans in my truck has a problem with the torque converter cycling. It locks up when the truck is under a slight load but when the throttle goes back to a cruise position, the TC unlocks. It appears to be working backwards.
This has been happening since I put this engine and trans in the truck. I hadn't worried about to much until now because I didn't drive it very far. Well now I want to start driving it more so I need to get it fixed. I am hoping to drive it to SlickStock instead of having it in the trailer.
I have pinned out all of the wires going from the trans to the PCM and everything appears to be correct. Power where it is supposed to be and wires going to the PCM are correct.
My code reader shows that the brake on off switch was not applied during key on engine running mode and I did do that. I pulled the harness off of the PCM and tested the BOO switch and I do have power going to the correct pin on the PCM when the brakes are applied.
Could have a problem with the PCM? The sevice manual says that the throttle position sensor is the only thing that will cause this and I have replaced it but it did not help. This is an OBD1 system so the TPS is not adjustable.

ANY IDEAS,

Kevin

[Arrowhead]

Well I notice this on newer vehicles all the time, but I think it's a fuel saving strategy. By unlocking the converter on "coast" it doesn't slow the vehicle down when you let off the gas and the result is better fuel economy at the expense of constantly dropping the the converter lockup clutch. And then it locks up again on acceleration. That is a little different than what you describe anyway.

Being you say yours is an OBD-I then I doubt it has this strategy. I can't really think of anything you haven't tried.

[cooter]

the convertor unlocks under heavy acceleration and also wont downshift if still locked. With this thought is it possible that the tranny unlocks because it thinks you are pulling hard? does the convertor lock in 3rd or only in overdrive?

[PFM-64f100]

Well first a couple of questions. What PCM are you running (HUG2, etc)? Do you have it chipped, maybe one you can program - quarterhorse, tweeker, etc?

If the boo is getting 12V when the brake pedal is applied then that is not your problem.

We have the same version (ODB-I) computers.

You can slightly adjust your TPS it won't move very far but give a little bit of adjustment (at least the factory ones you could). You will need to use a meter to read it unless you can do some data logging (via the chip).

One other thing to try, on your OSS and VSS sensor make sure the negative side has a connection to ground. Yes these are suppose to be internal grounded to the computer but my OSS would not give the correct signal to the computer until I tied that one side to ground. It has worked ever since.

Other than the above you will most likely have to program that shifting to do what you want. Might even be an adjustment on your CT TPS voltage.

Let me know, heck give me a call and we can talk. I've been through a lot with my tranny and PCM (mostly because of a bad rebuild shop in KC).

More I think about it, connect ground to Pin 6 (VSS (-)) , Pin 29 (TSS(-)), Pin 46 (SIG-RTN). That is how I have mine setup and it corrected a lot of problems early on.

http://oldfuelinjection.packrad.net/truckpinouts.html

[kstones63]

the convertor unlocks under heavy acceleration and also wont downshift if still locked. With this thought is it possible that the tranny unlocks because it thinks you are pulling hard? does the convertor lock in 3rd or only in overdrive?

The torque converter appears to not be locking up in 3rd gear at all. When you let off of the throttle at all, it unlocks the TC.

Well first a couple of questions. What PCM are you running (HUG2, etc)? Do you have it chipped, maybe one you can program - quarterhorse, tweeker, etc?

If the boo is getting 12V when the brake pedal is applied then that is not your problem.

We have the same version (ODB-I) computers.

You can slightly adjust your TPS it won't move very far but give a little bit of adjustment (at least the factory ones you could). You will need to use a meter to read it unless you can do some data logging (via the chip).

One other thing to try, on your OSS and VSS sensor make sure the negative side has a connection to ground. Yes these are suppose to be internal grounded to the computer but my OSS would not give the correct signal to the computer until I tied that one side to ground. It has worked ever since.

Other than the above you will most likely have to program that shifting to do what you want. Might even be an adjustment on your CT TPS voltage.

Let me know, heck give me a call and we can talk. I've been through a lot with my tranny and PCM (mostly because of a bad rebuild shop in KC).

More I think about it, connect ground to Pin 6 (VSS (-)) , Pin 29 (TSS(-)), Pin 46 (SIG-RTN). That is how I have mine setup and it corrected a lot of problems early on.

http://oldfuelinjection.packrad.net/truckpinouts.html

The BOO switch has power going to the ECM. The code reader isn't recognizing it.
The VSS has a connection to ground, I have checked that. The VSS and the OSS are on different circuits. The OSS does not have a connection to ground but it is on the same signal return wire with the TPS, the TC lockup solenoid and several other things. That's what makes me wonder if the ECM is not completing the ground circuit completely or if the TC lockup solenoid is bad. According to my manual, these sensors signal return wires appear to be in a closed circuit. There is not an external ground shown. It appears that the ECM is supposed to make the ground circuit complete. I would assume that if it wasn't working at all that the engine wouldn't hardly run with this may sensors attached to that 1 circuit.
I did have the BOO switch hooked up backwards and had power going to it all times instead of only when the brakes are applied. This makes me wonder if I damaged the ECM.

Chris, Send me your phone number and I will call you over the weekend. I know that you have experience with electronic transmissions.

Kevin