Hello all, New here. I've got a 84 Z28 with the lg4 305 auto. My ccurrent transmission is about shot. I just bought a rebuild trans from a 91 truck.


My question is, what problems may I run into with the differences in years. My trans is the original trans the car came with, but it's about done. The guy I bought it from used to rev up and bump shift from first to drive. But I'm wondering if I'll run into any problems with it being a newer 700r4, mine does not have that arch but the New one does.

 

I believe the early transmissions use 1 wire to control the torque converter lockup then later on, some time in the late 80s GM to a multi wire setup.

 

That's one thing I have heard, but not sure.

 

They may have used up to 3 wires, one is ground, the other is power for the torque converter lockup and I do not recall what the third wire is for, maybe VSS signal.

 

I guess my real questions are, what all will I have to change over, and how much of a pain in the *** will it all be?

 

Should bolt right in, although you'll need to swap over your existing tailshaft housing for the torque arm mount and speedo connection.

The wire connector should be the same. It controls converter lock and provides a fourth gear signal to the ECM.

 

The change to the 91 trans is a big improvement. The 700R4 was redesigned in 87 with impovements for increased strength. The 87+ units allow for alot more aftermarket performance and strength upgrades. As already stated, the units are interchangeable. The gear ratios are the same. Just the tail housing needs to be swapped.

 

Some 87 transmissions were cross over models, with some of the upgrades but no secondary valvebody (like the one in my garage that was replaced by a T56).

 

That one of my concerns, I few people have told me the differences in electronics may be a problem.

 

Confirm the truck transmission did not come out of a 4x4. They're shorter than RWD models. You can make the 4x4 trans work but it's a lot of bench work to go through.

 

It came out of a rwd. That was my first question to the guy.

 

You haven't swapped it in yet?

Go do it.

 

Lol trust me I'd love to, But I got to wait for my next check. Still got to get a New torque converter, and a New shift cable. I'm sure it being a newer model it's a 30 spline on the input shaft.

 

[QUOTE=AmSerl;5898720]That one of my concerns, I few people have told me the differences in electronics may be a problem.[/QUOTE

There are no electronics in the 700R4. Only the TCC lockup for which your 84 should only use one wire. There are pressure switches and possibly a temp switch for TCC control but your 84 probably won't use them. I can double check on Monday to be sure how the 84 is set up. The only electronic issue you might have would be if this 91 was a 4L60E, which is physically similar but electronically controlled.

Vehicles with electronic speedometer used a VSS rather than cable but the parts are in the tail housing. I'll look into it Monday at the shop. You never want to reuse the converter from a high mile transmission anyway. It would be filled with crap that can only be cleaned out by cutting it apart.

Yes the upgrades I mentioned earlier were made mid year 87. The point is, the 91 will benefit from them. In fact there were numerous changes made throughout production and different setups for different applications. Many of the differences were in the 3-4 clutch. That's all subject to change in a rebuild too. There are as many possible variations in a 700R4 build as there are parts in the unit.

 

If there is any part of the TCC control that didn't convert, there are simple TCC lockup kits available to make it work.

 

By chance could someone point me in the direction of one of these kits.

 

Yea, Summit has them for about $80. Got one in my '64 Impala.

 

[QUOTE=ASE doc;5899061]Is there a chance of me running into problems with the tcc? I'm doing the swap soon because my trans is done.

 

If you cannot figure out the wiring to make it lockup, then go with the Painless vacuum lockup kit here. It will do everything that you want. It will lockup in the 3rd & 4th at part to medium throttle, will unlock when you floor it, will unlock when you let off the throttle and will unlock when you apply the brakes. Shop around for the best price on the Painless kit. Make sure that the TV cable is tight at WOT.