Hey guys, just picked up a used 1991 T-5, and am putting it in my 89 IROC that has a mechanical speedometer, but the 1991 T-5 uses an electronic speedo. Can I screw in a mechanical speedo into the trany from a older V6 non-WC T-5?

If not where can I buy the mechanical unit, or is it easier just to upgrade my guage cluster? And if so, where is the best place to buy a new guage cluster?

I understand that i'll have to replace the speedo gear on the output shaft to get an acurate speed, just not sure what the easiest path forward is. Thanks.

 

I'm surprised you couldnt find this answer in a search.
The mechanical and electronic speedo units in the trans are identical in size. They are a direct swap for each other. The speedo gear that goes on the units are different however.

 

Actually, if you get the mechanical speedo sender that uses the metal shaft, it's the exact same plastic gear w/d-shaped hole that the electric VSS unit uses. It's definitely way cheaper and easier to go this route rather than try to convert your gauge cluster to the electric speedo style. If you can't manage to find a metal shaft mechanical sender, you can also buy a brand new mechanical speedo bullet that uses the all plastic gear instead. The all plastic gears are still available just about anywhere, and the matching speedo bullet is the same one that the TH350's and old school 4 speed trannys use, so they're extremely easy to buy new as well. A lot of the original T5 mechanical speedo bullets used the metal shaft, so it really wouldn't be too hard to find a used one somewhere. I grab them out of 6 cylinder T5 cars all the time at the boneyards.