I changed my rearend gears from 273 to 342 in my 90 camaro. There is a drac unit located in the car that i can not fine. From what I understand to fix this problem i change a few wires. Thanks

 

on these cars I think it is on the back of the cluster


but I think you just need to change the speedo gears in the trans?

 

im not sure if its still there on the 90....but im leaning more towards the yes side.

look under the car and see on the driver side where the speedo cable goin into the trans. take off 1 bolt (10 or 12 mm i believe),take off a little "C" shaped bracket and pull the speedo gear straight out. youll have to find out what gear you will need to put back in accordoing to ur ratio (3.42 for u).

 

A 90 will be electronic, but I know the first fourth gen(93) still used the gears w/VSS(just like the 85+(?) firebirds)