Here's the deal, I want to swap my burned out 85 700r4 to a good 91 700r4. My car is an 85 z28 with a 5.0 TPI and the new tranny came from a 90 RS with a 5.0 TBI. What am I going to have to change in order for the newer tranny to work in my car? Thanks for any help.

 

A 1991 700R4 will have a lockup converter that is controlled (activated) by the ECM... Your 1985 unit and vehicle is not... I believe that there is a hydraulic circuit in the valve body on the '82-'86 units that control the converter clutch... This circuit is replaced by an aluminum plug in the 1991..

Simplest way would be to wire a manual switch to lockup the converter... Once you get on the highway, just flip the switch and enjoy the mileage.. Just make sure to run the circuit through your brake switch so the converter clutch disengages when you step on the brakes.. You can alter the wiring in the '91 unit to only allow the lockup solenoid to be activated in 4th gear by using a pressure switch in the valve body to provide ground for the solenoid.. Then use a relay and switch to provide power to the A terminal on the transmission wiring plug... Wire position D to ground and you'll be set... I think there is a more in depth article on configuring a manual torque converter lockup switch somewhere on this site...

Other than that the transmission will function just fine as a direct replacement for your '85 unit...

Someone correct me if I'm wrong about the hydraulic control vs ecm control years...

 

Put the 85 speedometer drive gear (requires removal of the tailhousing) on the 91 trans. Use the 85 speedo driven gear & sleeve. That's it.

I'm 99.9% sure the pre-88 700's had the same exact TCC wiring as the later ones & were ECM controlled. Matter of fact, the 86 IROC my TPI came from had the same lockup wiring as a 90 or 91, so I don't think you'll have to concern yourself with that at all.

 

okay, so who's right?

 

I'd put $ on me being right.

But just to appease the archival wonderfulness of this site, I'll try & get a pic of an 86 700-R4 and a 91 700-R4 this weekend.

Seems to me that you have an 85 700-R4 in your car. Go look at the TCC plug on the drivers side. It should be a 4 pin square weatherpak. Which is... just like 91.

 

85 tranny in my camaro......4pin weatherpack, even used a B&M lockup kit for it.....just for mech. speedo is the only difference. my .02.

 

Converter clutch system is the same. Same connector even. Speedo is the only difference, which can be transferred from one ot the other.

Ignore the post about different lockup control, it's wrong.

 

I'm running an 89 in my 85 and the shifting was never a problem other than the shift points. I would not get rid of the 85 trans too quickly as you may want to swap governors or mix and match springs on it to get it to upshift at 5000 instead of 4,500. 85 TPI had a little more cam than the 91 TBI.....

 

Perhaps it was just some of the early trucks that had no ECM control...

 

Yeah, a lot of truck stuff doesn't apply. Diesels and probably others used a lockup harness that wasn't used in cars. Their "part CCC" Q-jets are also unique to them also, although there were some TPS only Q-jets in the late 70's in cars.

I believe one year of the 200-4R was made with a hydraulic lockup circuit.

But f-bodies had ECM's since 81 at least; no reason for them not to run lockup off it.

 

Thanks for the help. One more question though. Are the splines going to be the same or are there different number of splines for the tc and ds between years 85 and 91?

 

Mid 84 is when they went to the higher # of splines so 85 and 91 interchange no problem.

Early 84 and before converters interchange with the 200-4R.