700R4 Lockup Issues After Rebuild

[RollinTurd]

Hey folks! Dont post much, but sure do learn a lot from all the other posts. Ive got an 88 C1500 5.7 with 190K on the clock. Also running EBL Flash II. Trans was slipping in lockup and had it rebuilt recently by a reputable local shop less than 100 miles ago. Overall, very pleased with the transmission. Got some upgraded parts in preparation for my 383 if that day ever comes.

Issues:

1. EBL Flash II no longer recognizes the gear that the tranny is in. Prior to rebuild would show P, N, D, and OD.
-EBL shows 0 for gear indicator
-How did the ECM know which gear the tranny was in??

2. Lockup only works in 4th, and seems to be on a short time delay engagement.
-had lockup in 3rd and 4th before rebuild
-lockup would disengage with engine load before rebuild not after
-lockup indicator in EBL Whats Up Display does not match what the tranny is actually doing

3. I think i got my transmission back, but not 100% sure.
-Going to check the codes per Nick's writeup to see if its close
-Any other ways to tell?

Talked to my transmission guy today to ask if any changes were made to alter lockup, and he said the only thing he changed was adding a jumper wire over the lockup temp switch.

Hoping one of you or @NickTransmissions can shed some light on this or give some ideas of where to start. I know I'm probably going to have to drop the pan but want to avoid it if possible. Should have went with a plugged drain pan...hindsight...

 

[scott2093]

lockup would disengage with engine load before rebuild not after

Does it disengage with brake pedal depressed? Not that it's relevant or if yours works like that, I don't know, but maybe the more clues the better until someone chimes in....

 

[RollinTurd]

Yes it disengages with brake pedal, but locks up immediately on release of pedal.

 

[Sean Buick 76]

Did you get a new torque converter? I would add a toggle switch to the lockup function so you can determine if the issue is the the solenoids inside the trans or if it’s the external electrical issue with lockup wiring. Once sorted go back to the factory setup, use the toggle switch to help diagnose it. I actually liked the toggle switch and left it using the switch for years.

 

[GoToGuy]

If your having problems, shouldn't your first choice be taking it to the rebuilder ? If you mess with it, will it void any warranty?

 

[NickTransmissions]

Hey folks! Dont post much, but sure do learn a lot from all the other posts. Ive got an 88 C1500 5.7 with 190K on the clock. Also running EBL Flash II. Trans was slipping in lockup and had it rebuilt recently by a reputable local shop less than 100 miles ago. Overall, very pleased with the transmission. Got some upgraded parts in preparation for my 383 if that day ever comes.

Issues:

1. EBL Flash II no longer recognizes the gear that the tranny is in. Prior to rebuild would show P, N, D, and OD.
-EBL shows 0 for gear indicator
-How did the ECM know which gear the tranny was in??

2. Lockup only works in 4th, and seems to be on a short time delay engagement.
-had lockup in 3rd and 4th before rebuild
-lockup would disengage with engine load before rebuild not after
-lockup indicator in EBL Whats Up Display does not match what the tranny is actually doing

3. I think i got my transmission back, but not 100% sure.
-Going to check the codes per Nick's writeup to see if its close
-Any other ways to tell?

Talked to my transmission guy today to ask if any changes were made to alter lockup, and he said the only thing he changed was adding a jumper wire over the lockup temp switch.

Hoping one of you or @NickTransmissions can shed some light on this or give some ideas of where to start. I know I'm probably going to have to drop the pan but want to avoid it if possible. Should have went with a plugged drain pan...hindsight...

Take it back to the builder, have him fix it. If he had the entire vehicle and your issues arose only after it was at his shop, its highly likely something impacting your TCC apply circuits (electrical and mechanical) either materially changed like diff/wrong parts installed or something may have been misassembled.

Everyone makes mistakes and/or stuff happens (nature of the beast when it comes to auto repair) but it's incumbent upon him to correct any issues related to his work. At the very least, let him take a look. If the cause of the problems lie outside of what he did, he'll need to document it and be able to show you exactly what went wrong and why it's something outside of his doing.

Dont mess with anything yourself unless you know exactly what to do (im guessing you dont given you're asking for help).

 

[RollinTurd]

Thanks for the replies!

I did figure out I had the EBL Flash II configured incorrectly. Indicator within the WUD is now displaying correctly. My "truck" laptop died and I missed the auto/manual setting when I reinstalled the Dynamic EFI software on the new laptop... The ECM must somehow read off of the pressure switch activations? ECM definitely knows when it shifts into OD.

I did get a new torque converter with the build. Not exactly sure what it is, but he said it was a better factory one with the Allison style bushing in it whatever that means.

@NickTransmissions , he did not have the whole vehicle. I pulled the trans and took it to him because he didn't have space/time to get me in with the whole vehicle. He did turn it around in 2.5 weeks with just the tranny to get me back on the road for deer season.

When I talked to him today his solution was to put a vacuum switch on it or a manual switch on the dash. He said the only changes he made to lockup was bypassing the lockup temperature switch with a jumper wire.

Not planning on messing with anything inside the trans, but just trying to verify work done. If that means dropping the pan, identifying the valve body, verifying the wiring, etc, Im 100% comfortable doing that.

 

[Erik the Awful]

When I talked to him today his solution was to put a vacuum switch on it or a manual switch on the dash. He said the only changes he made to lockup was bypassing the lockup temperature switch with a jumper wire.

That's not fixing it, that's a hack. I'd ask him to fix it right.

 

[RollinTurd]

@NickTransmissions , I know you told me to leave it alone, but Im trying to prove that I didn't get back what I took him or at least got a different valve body.

Can you take a look at these pics and let me know what you think? I dropped the pan and found what looks to be the hydraulic valve body not the electronic valve body... I think this confirms my suspicions... Same numbers as in your video of the early 87 valve body and the open port for the hydraulic TCC.

Also in your valve body video you called the switch beside the 4th gear pressure switch a 3/4 pulse valve(?). My trans guy called it a temp switch. You can see the jumper he made in one of the pics to remove the "temp switch". Is he calling the same switch by a different name?

@Erik the Awful , I feel kind of hacked right now...

 

[RollinTurd]

Also in your valve body video you called the switch beside the 4th gear pressure switch a 3/4 pulse valve(?). My trans guy called it a temp switch. You can see the jumper he made in one of the pics to remove the "temp switch". Is he calling the same switch by a different name?

I answered my own question here. Temp sensor and 3/4 pulse switch are two separate parts. The temp sensor sits in a sheet metal bracket in there just connected to the wiring not screwed into a port. The plugged port is where the 3/4 pressure switch would go.

Is the removal of the temperature switch and addition of the jumper wire enough to confuse the ECM?