TCU and 4L80e quesitons

[critter]

Russ, thanks to you and Chris for your help. The tip on doing the wide open TPS setting and checking pressure should help.

[critter]

I decided to ohm out the harness first. It passed with flying colors. So I guess I'm down to the TCU or the force motor (pressure control solenoid.). I'll ask the experts again and see what they think I should do next. Is there a way to bench test the TCU?

[critter]

I installed a 12V power supply and read amperage across the C and D poles of the transmission connector. It's feeding the information to the transmission. More to come.

[critter]

Tonight I managed to get back to the shop. I did what TCI had asked and started the car with the linkage to the TPS disconnected. Then I had an assistant pull the TPS open while I watched the pressure gauge. Sure enough, it came up to 100psi at idle with the TPS held at the WOT position.

I then loaded the fresh TCU file that they provided and then recalibrated the TPS. I took it for a short drive and I did feel it shift. I was data logging so I didn't look at the real time display. I was watching line pressure. It came up to 100psi off idle and seemed to stay in that range most of the time.

The car still feels mushy on the shifts but at least it shifted.

Tonight I managed to get back to the shop. I did what TCI had asked and started the car with the linkage to the TPS disconnected. Then I had an assistant pull the TPS open while I watched the pressure gauge. Sure enough, it came up to 100psi at idle with the TPS held at the WOT position.

I then loaded the fresh TCU file that they provided and then recalibrated the TPS. I took it for a short drive and I did feel it shift. I was data logging so I didn't look at the real time display. I was watching line pressure. It came up to 100psi off idle and seemed to stay in that range most of the time.

The car still feels mushy on the shifts but at least it shifted.

Chris,

I need you to load up the File that I had sent to you. I do not want you to drive the car with low line pressure or you will be tossing money out the window. There should be some line pressure at idle with the TPS calibrated correctly. At part throttle it would be 150-220psi range at WOT it should be 250+psi.

So if you can load up the file that i sent to you and check the line pressure at 2000rpm with the vehicle warm. and then check it at 2000rpm with the TPS at WOT.

thank you

Russ

[critter]

Can do Russ. Sorry for the scattered approach. Your advice was spot on with the TPS so I'll follow these instructions and get back to you. It might be a few days but I see this as progress.

[critter]

Per your instructions the tests revealed the following pressures:

idle - 20 psi

2000rpm, part throttle - 90-100 psi

2000rpm, TPS at WOT position - 150 psi

What's next?

[critter]

OK, per your instructions our transmission builder went back through and looked. We can find no mechanical issues with the transmission. He did suggest that a TransGo HD2 shift kit would bump pressures slightly and we intend to do that but he said to do the following.

Disconnect the transmission harness and put it in "limp mode".

Read the pressures in P D and R at 1500 rpm.

We did and got the following:

P, D - 170psi

R - 320psi

He indicated to me and I double checked using the ATSG guide that those numbers are correct. So if the transmission has the proper pressure in this test does it not indicate that we still have an issue with the computer telling the transmission what to do?

I'm sorry guys but I'm getting stuck in a finger pointing contest here.

[critter]

One more question. How important is the geometery of the cable setup on the TPS? I'm using a Quadrajet that was not designed for use with a kick down cable. I added the stud to attach the cable for the TPS to the throttle linkage, just ahead of the hole where the return spring is connected.

[Cameron@TCI]

OK, per your instructions our transmission builder went back through and looked. We can find no mechanical issues with the transmission. He did suggest that a TransGo HD2 shift kit would bump pressures slightly and we intend to do that but he said to do the following.

Disconnect the transmission harness and put it in "limp mode".

Read the pressures in P D and R at 1500 rpm.

We did and got the following:

P, D - 170psi

R - 320psi

He indicated to me and I double checked using the ATSG guide that those numbers are correct. So if the transmission has the proper pressure in this test does it not indicate that we still have an issue with the computer telling the transmission what to do?

I'm sorry guys but I'm getting stuck in a finger pointing contest here.

Critter,

Russ is out until Thursday.

Those pressures do not indicate any issue with the controller. This is not a matter pointer fingers, simply looking at other possible causes. When the transmission is connected with the TCU, the TCU simply works off of the duty cycle provided in the program. It then sends amperage to a force motor solenoid. If the line pressure changes through out the sweep of the TPS the TCU is working.

Since you have an ATSG book, I would suggest checking the line pressure per its instructions. Checking line pressure with line pressure gauge on an 80E is only half of the battle. You actually have to use something similar to a "Zoom Box". This allows full operation of the trans remotely. You are also then able to change the amperage to the force motor as needed to properly check the line pressure. If the force motor is not working properly, the transmission (when hooked to a controller) may not make the correct pressure.

I would personally say the the force motor solenoid is bad. When in LIMP MODE the force motor allows max line pressure because it has no amperage to it. As the amperage increases and decreases to the force motor, the line pressure will increase and decrease appropriately.

Have your trans guy look at that.

Thanks,