700R4 Lockup Issues After Rebuild

[NickTransmissions]

@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...

You have a first design valve body with a 2nd design 1-2 shift valve train installed onto the transmission per your pics above...Tells me it's a 1987 valve body...Since you have a 1988, you should have a second design valve body but it's possible that

a) the shop swapped valve bodies because the builder felt there was issues with the original valve body (you can install a 1st design valve body onto an aux vb case but you cannot install a 2nd design valve body onto a non-aux case)

b) That is the original valve body, as installed at the factory simply due to those VBs still sitting on the shelf...

You can tell it's a first design valve body by the existing of the TCC control bore being cast into the valve body (2nd design valve bodies don't have it - the housing has nothing there on a later VB).

The temp sensor can trigger TCC apply if it hits a certain threshold since less heat is generated when the TCC is enabled. That said, I would have put a Rostra replacement harness vs reuse the original given it's age. Here's an example from a 1987 unit I just got done building; it has the same exact valve body that you have and replacement Rostra harness installed.

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[NickTransmissions]

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?

Yep, two separate parts as you mentioned...Why did he modify the set up to bypass the temp switch and install a 'jumper wire'?

Also, do you have a picture of your valve body prior to bring him the transmission? That's the only way any of us (and possibly you as well) are going to be able to tell if the VB was swapped while in his possession. As mentioned in my post above, sometimes I have to swap parts like that but the customer is always made aware of such a swap and why I'm doing it so they have an opportunity to voice any concerns...In the case of swapping a 2nd design vb for a first design vb, it's usually done in resto-mod vehicles where there is no on-board computer and the owner doesn't want to install any internal-external electromechanical lock up kit to work the converter clutch.

 

[PlayingWithTBI]

IIRC, there are 2 wires (among others) that tell your ECM the trans is in P/N or D on one and D or OD on the other. After you switched your bit in the .bin to Auto instead of Manual, does it now show that?

 

[RollinTurd]

Yep, two separate parts as you mentioned...Why did he modify the set up to bypass the temp switch and install a 'jumper wire'?

Also, do you have a picture of your valve body prior to bring him the transmission? That's the only way any of us (and possibly you as well) are going to be able to tell if the VB was swapped while in his possession. As mentioned in my post above, sometimes I have to swap parts like that but the customer is always made aware of such a swap and why I'm doing it so they have an opportunity to voice any concerns...In the case of swapping a 2nd design vb for a first design vb, it's usually done in resto-mod vehicles where there is no on-board computer and the owner doesn't want to install any internal-external electromechanical lock up kit to work the converter clutch.

Thanks @NickTransmissions for the responses! He said he bypassed the switch because they often go bad and cause problems.

I always take pictures except for this time. Feel pretty dumb for not doing it.

Does the 1st design VB override hydraulically what the ECM would be commanding? Said differently can the ECM still control lockup on a 1st design VB?

Rostra harness is already on its way!

They are closed today but will find out tomorrow if they switched cases and or valve body.

 

[RollinTurd]

IIRC, there are 2 wires (among others) that tell your ECM the trans is in P/N or D on one and D or OD on the other. After you switched your bit in the .bin to Auto instead of Manual, does it now show that?

Yep all good here now. Just the lockup issues now.

 

[NickTransmissions]

Thanks @NickTransmissions for the responses! He said he bypassed the switch because they often go bad and cause problems.

I always take pictures except for this time. Feel pretty dumb for not doing it.

Does the 1st design VB override hydraulically what the ECM would be commanding? Said differently can the ECM still control lockup on a 1st design VB?

Rostra harness is already on its way!

They are closed today but will find out tomorrow if they switched cases and or valve body.

You're welcome...They will 'compete' with each other to control the TCC Apply valve in the pump, which directly commands the torque converter's clutch on and off so I'd never install both in the same 700R4...The valve body in your transmission now has two 'inert' aluminum slugs that do nothing so as not to interfere with the electro-mechanical TCC control system.

If you wanted to, you can disconnect that system (simply unplug the connector at the transmission and install a Transgo or Superior Technologies mechanical TCC lock up kit which consists of a TCC apply and throttle valve - these two valves (one is in an aluminum sleeve and installed in the outboard position) will lock your converter once you're over 40 mph (there's different springs to change the lock up speed) and unlock once you put your foot into the throttle or hit the brakes and the trans downshifts.

 

[RollinTurd]

Transmission is fixed! Dad and I searched and found multiple wiring diagrams, but they didn't all agree. Then I remembered someone posted on here about charm.il and all of the online manuals on that site. BAM they had one that made sense to Dad and pointed to the jumper wire in place of the temp switch.

Pulled the jumper wire out of the connector, filled her up, test drive, and ECM is back in control of lockup!

There is conflicting info on that temp switch. Some say it's to prevent lockup to help the trans warm up, and others say it's to force lockup to help the trans cool down which is what @NickTransmissions said above. Mine was definitely the latter so the jumper was forcing it and overriding the ECM.

I suspect both are possibilities depending if it's a northern or southern climate intended vehicle. This is suspicion only not fact, but there are diagrams that show normally closed and normally open for that temp switch...

I got my temp sensor from the trans guy today and plan on testing how it works.

Dad is also going to write up how he realized what was wrong. The electrical stuff is a little over my head... I'm going to document the diagrams and the one post on a different forum that made it all click for him.

Thanks to everyone that helped on this!

 

[tayto]

putting a jumper wire on the temp sensor will cause it to lockup immediately when it shifts into 4th gear