In my '82 Z28 I have the factory T10 4 speed.The car came original with 3.23's in the rear.I since have installed 3.73's into the car.My speedo is way off obviously and I have no idea where to start to correct it.I know it is a matter of changing speedo and driven gears..but to what?Has anyone done this gear swap with a T10??What is the formula to calculate how far off my speedo is?I am trying to figure out fuel mileage along with correcting the speedo reading and even with my speedo being off I am coming up with some pretty good numbers for my combo.They can't be right.Any and all help is much appreciated.TIA

 

It's the same gears as a T-5, except that the drive gear is the other inner diameter.

7 (blue) and 22 (red) IIRC are the gears you need. You probably already have the 7 blue drive gear, and a 19 white driven.

 

When I swapped in my latest motor I remember cleaning the gear on the end of the speedo cable (got some dirt on it from dragging on the ground when trans was out) and I am positive that one was red.That is the driven gear correct?That is the other part that confuses me.It was like 2 years ago now but for some reason I recall 11 teeth.I will have to pull it out again and recount to see for sure and get back to you.Only other question is..Where do I get the gears for this swap?Right at GM..or???Thanks again for all your help RB83L69..

 

AFAIK the dealer is the only place...