Hi, rebuilding a 4x4 1990 700r4 this will be 2nd time in about 6 years. The transmission has no lockup or I should say no electrial wiring. I read some posts on here saying all 700r4's are lockup? Do some lockup without wiring? Anyway my question is what happens if I use a lock up torque convertor on a non lockup 700r4? Most new auto store converters say lockup.

 

They are all lock-up unless you install a non-lock-up converter. If the converter does not lock up in 4th gear, it will overheat (unless your rear-end gear ratio is extremely low) due to constantly spinning below the converter's stall speed.
If the vehicle does not have the factory ECM, an after-market lock-up system should be used, like the one I got from Monster Transmission...

 

Thanks for the info, it does have 1227747 ecm. 4:10 ratio that's normally driven offroad. I don't want to limit it to offroad though. I don't see how the computer can lock it up if there is no electrical wiring or even a place for electrical wiring on the 700R4. I could buy the transmission parts and wire into the ecm. If it will add reliability.

 

Painless Performance Lock-Up, Part #60109

 

Thanks for the info. I think the 700r4 also had a mechanical lock up version that has no wires but still locks up. I will know if that's the version I have in a couple hours. Once I get the pan off and look at valve body. I was pulling the trans out last nite. I have no third gear and torque convertor looks like it was hot and no paint on it. I'm definatly going to make sure it locks up. But also try to keep it cooler offroad where I can hopefully find room for a trans cooler with a fan that can handle mud/water or get out of the way somewhere.

 

I believe this is what your referring to:

https://transgo.com/product-details/...aulic-lock-up/

BUT !!!!

There appears to be one important caveat;

(Excerpt from the above link)

"This TransGo kit does not require any electric connection for lock-up operation. However, the kit requires the valve body to be factory machined for the inner and outer valve train that may be currently occupied by the OE dummy plugs or existing valve train."

 

Yes...

Many Early Valve-Bodies (1987 and Older) had Hydraulic Lock-Up Valve-Train or Dummy-Plugs.

None had both the Hydraulic Lock-Up Valve-Train and the Electrical Components for Lock-Up.
Dummy-Plugs were in some Valve-Bodies that had the Electrical Components for Lock-Up.

The TransGo Valve-Train can be used to replace the Dummy-Plugs.

 

Thank you both. So it doesn't have the machining in the valve body for the manual lock up. I wish I could use the numbers to ID this year but the numbers on tag don't make sense to me. I think that transgo lockup kit is my best bet.
I tore it most of the way down today and the 3/4 clutches looked like toast. I rebuilt this once about 10 years ago and for some reason thought it was an art car trans. But I can't remember why I thought that.

see if anyone can make sense of this ID plat

e.

 

You have a GM SRTA (Service Replacement Transmission Assembly)...

It is a Transmission that GM rebuilt and resold.

The Original ID Stamping has been ground down, then re-stamped with the STRA #.

There is no way to ID what it originally was.

 

I appreacite that nformation. Just my luck.. I'm close to getting another core just so I know what to buy for the rebuild. But if anyone has ways to identify which rebuild kit I would need or anything else that can help identify the year. That would be helpful. Reading the 700r4 ATSG manual and so many things depending on the year and different calibration sensitive 3/4 clutch stack up. Everything keeps referring to the trans codes.

 

You are most welcome!


I also have an Automotive Electrical Business...
Is JP Custom Controls actively in business? does not appear to be working.

...The Hyper-Link in your Signature (http://www.customswitchcontrols.com) does not appear to be working.

 

I probably need to update my signature here, ive been out of the hobby and not on here a long time. Many years ago I had a small side business making control panels and harnesses for mostly offroad vehicals. It helped me buy more parts and something to do. I now make microcontrollers and sometimes apps on the side but not much automotive and don't sell anything.
But my real day job is a commissioning engineer for Cummins. I work on large generator parallelling and switch gear systems for hospitals, data centers, etc. I will definatly check out you're site.

 

I’ve used this TCI piece and it works great. You have to redo the wiring on the valve body and add their sensor in place of the original at the 4th gear spot on the valve body. Super easy and quick to do. On the outside one wire to ignition and a vacuum hose to ported vac source. It locks up when in 4th gear and vacuum is above 10”. I raise it to around 14” and it feels like stock. It’s locked while cruising and will unlock as soon as you let the gas pedal go and let you coast instead of engine braking.

https://www.summitracing.com/parts/tci-376600

 

Thanks. I was just looking at that. So mine has no solinoid or anything in it for TCC. Not even a wiring connector in the case. I do belive its 87-92 though now. It runs the 1227747 ecm ASDU which should be capable and already programmed to lock it up. Looking though the Haynes manual it has 2 wires dedicated at ECM for TC lockup. I assume I will still need that solinoid with that kit but doable.

I found this rebuild kit from PATC which includes the master rebuild kit and TCC lockup says "included" but no pics or anymore details of what exactly included for the tcc lockup I mean 1k is pricy for a old jeep and mud But this transplant doing the same repair multiple times sucks I don't have many miles on this rebuild. I'm thinking it's a heat issue. I rarely drive highway but I want it to be rite. Here is the whole kit.

https://transmissioncenter.net/shop/...real-deal-kit/

I know this. Much. I will never not have a temp sensor in trans anymore. If I had one would've likely seen this coming. I'm going to add a sender and guage for temp. Hell maybe even pressure. Lol.

 

Well tore it the rest of the way down and I think I found the problem. But I also remember I didn't rebuild this last. When it failed I had a shop do It. So I'm not sure if this is the problem or some upgrade or update to the accumulator.
the 3-4 accumulater seems to have an extra piston and no 3-4 accumulater spring and one of them has no seal either. Behind it came out pure black fluid all grit. Here is a picture of how it was in there. Unless I did this by accident and the trans shop did it the same way. I have no idea. Here is a picture showing how it was in the bore. Can anyone tell me what would fail if anything when installed like this? And without the 3/4 spring?

 

That is a Lazy-Man's way to make the 3-4 Up-Shift a bit more firm.
As long as one of the Pistons Seals, than there is no issue.

Locations like that Bore in the Case always collect Debris because it has no where to go from that point.

 

Thanks again. I'll do something different with that. We'll I think we're good to go. I apprecaite everyone's help. I'm going to get some parts to make the tcc lookup with a toggle switch override the ECM. Definatly adding temp sender to make sure i can monitor temp.