I have an '88 firebird with electronic speedo. I bought a '83 t-5 with a mechanical speedo. Could I have info on how to change this over. I dont care if I need to change the speedo itself or if I have to change the cable out of the tranny. Any help would be great! anything would be very much appreciated.

 

Does your 88 have an auto or manual trans in it right now? If it already has a manual trans, all you have to do is re-use your existing electric VSS unit in the other trans. They fit in the same hole as the cable drive. If you're switching from an auto to a manual, you'll need to locate a T5 VSS unit as they're totally different from the 700r4 VSS unit.
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I just noticed your other post stating that you currently have a 700r4, so you'll definitely need to get a T5 style VSS somewhere. You'll also need the correct driven gear for whatever your rearend ratio is right now. Come to think of it, you probably have 2.73 gears right now with the TBI and 700r4. You'll want to at least upgrade to a 3.08 ratio or better. 3.23 or 3.42 would be ideal. Your car will be a total dog taking off with 2.73's and a manual trans.

 

I actually have 3.73's in it right now. I have to find the vss. Do drive/driven gears from a mechanical speedo fit into a t-5 VSS??

 

If your mechanical drive gear has the metal driveshaft where the gear just fits on the d-shaped end of the metal shaft, then it should swap right onto the vss unit. I have an extra T5 vss unit if you're interested. If so, just PM me.