joe73vette

I just came back from a salvage yard that is going to get me a 700r4 tranny out of an 88-92 Z/28 IROC T/A, but the guy wasn't too clear on the differences, so I am a little leary. How can I tell that I will be getting what I asked for when I pick it up? The archived topics only say they have the better servos and valve body, but not how to tell them apart. Thanks, Joe

BSeery

They may have better valve bodies and servos, but they're not the best you can have.

Replace the servos with either Corvette servos or those made by companines like B&M / TCI / Bow Tie Overdrives. Same for the boost valve. Get one that will let the transmission upshift from 3rd to 4th at full throttle and won't down shift 4-3 until 2/3rds throttle. A new / improved pump is a must as well.
Plan on putting a Trans Go shift improver kit in whatever you get.

Make sure it is a 30 spline input shaft. Previous versions were 27 spline and were weaker transmission.

joe73vette

I thought the Z/28 IROC T/A trannys had the full throttle 4th gear valve too, is it just the vettes? Are Z/28's any better than run of the mill 700r4's? Would a truck tranny be as good a starting point then? I'd like to run this for the summer then rebuild over the winter. Joe




[Modified by joe73vette, 1:22 PM 5/23/2004]

joe73vette

ttt

BSeery

You might have to get the casting number / part number and do a cross reference to see what internal components it had (Corvette servo and better throttle valve). Or just go to a Chevy parts department, ask them to look up the throttle valve out of a 89 Corvette and see if it's the same part number as in a '89 IROC.
I would rebuild it before putting it into the car. It's a lot easier than pulling it back out. Besides, if not built right and then driven, much more expensive components can be trashed.

When rebuilding plan on addressing the following:
All new seals and gaskets.
New - and I would get high performance - friction material in all the clutch packs.
Replace the TCC solenoid (easier now than later).
A high performance pump.
Larger servo.
A larger boost valve.
Change the governor to get you higher shift points (especially if you get a truck transmission).
A pan with a drain plug and then put a temp gage on it.

Look at the Trans Go rebuild kit for a starter. Here is some more info to look at. http://www.drivetrain.com/700R4_eautotrans/700R4.html http://www.4wheeloffroad.com/techarticles/63498/ http://www.tciauto.com/service_kits/

page62

I don't think there are many success stories of taking ANY junkyard 700R4 and installing it. They just weren't that strong originally.

biggjimm

Joe the Iroc and TA tranny's have three bolt holes going through the tailshaft housing horizontally from left to right. This is where the torque arm bracket bolts up. If it doesnt have the bolt holes it is not out of a IROC or TA. Good luck. Biggjimm

joe73vette

Bseery thanks fo rthe websites, I can do this myself!

biggjimm, I forgot about that. So not all Firebirds and Camaros had that torque arm? Maybe I should get a truck tranny?

Thanks, Joe