I have an 84' Firebird with the automatic 700r4 Transmission. So my question is will a trans from say a 1984-1987 work without modding anything? I know they started putting Electric speedo's on the newer models but wasnt sure what years. Thanks for the help.

 

It's very easy to swap the speedo drove stuff if you have the transmission on the bench so don't worry about that.

If you are looking for a more reliable, but used, stock transmission, then you are looking for the 87-93 700R4/4L60. You need to re-use your tailshaft housing for the torque arm hookup and your speedometer drive. You can use a transmission from most V8 applications in those years. The 4.3 V6 transmissions have some weaker guts (I think) and the Corvette has a different length tailshaft (I think) so I'd stay away from those. There are still plenty of cars and trucks that had those transmissions, though, so you should be able to get one easily.

You may need to take off the oil pan and remove your TCC solenoid. I think 84 used a positive signal to apply the solenoid and the later ones used a ground, but I can't remember now... I have seen people who put later transmissions in and then the torque converter stayed locked up all the time until they switched the solenoid and wiring plug. Just use the parts from your transmission now.

 

So i wouldnt have any problem changing them out? Is swapping the TCC solnoid and the tailhousing pretty difficult? Im most likely going with a good used transmission. Are these transmissions difficult to swap out in the thirdgens?

 

Im going through something similar. Easiest thing is to keep you mechanical speedo cable and use the old drive gear and bullet into the new transmission. You may have to change the speedo gear to correct the speed if the transmission originally came with a different rear.

Also the 700 from a 4.3 V6 usually is cheaper to buy and they have the same internal hard parts, only fewer friction plate count, which is easily corrected.

I seen a tranny guy say that all the 4.3 700r4 transmissions he rebuilt all had the v-8 clutch pack friction counts and smaller boost valves.

Here is a good read.

http://www.73-87.com/7387garage/drivetrain/speedo.htm