Originally Posted by canadamaro
Honestly we're not exactly sure what is in this thing. We got under there on the weekend and pulled this off the tranny '8MZM301B'
Are you sure that's not an 8YZM?
8 = 1988, MZM is the transmission ID code. 8YZM is a 1988 700R4.
The plug in the tail shaft doesn't really matter. It's the plug above the pan you're looking for. 700R4/4L60s have 4 pins, 93 4L60s have 5 pins, 4L60-E's have several more pins (12?). Look for the TV cable, and MD8 in large letters on the passenger's side of the bellhousing. If you have 4 pins, a TV cable, and the MD8 code, it's a 700R4.
Really, thirdgens are pretty limited when it comes to transmissions that will bolt in. Because the torque arm bolts to the transmission's tail shaft, only third and fourth gen transmissions will bolt up without aftermarket parts. It's a lot more likely you've got a 700R4 from a Firebird that had electronic speedometers starting as early as 1986, than a 4L60-E.
If it is a 700R4, you just need the mechanical speedometer parts. The tailshaft housings are the same, you just remove the clip holding in the sensor, pull out the sensor, and slide in the driven gear and sleeve, replace the clip, and screw in the speedometer cable. The only tricky part is getting the right drive gear, driven gear, and sleeve to match your rear gear ratio.