I've got an 88 GTA that I bought without an engine or transmission. After installing a 305 TPI with a 700R4 in it the speedometer and Odometer are way off.

Using the highway mile markers, going 1 mile my odometer says 1.3 miles. This has an electronic pickup for the Speedomter. Do I need a smaller or larger gear?

is there a way to calculate how much different in size I need?

where is a good source to purchase this?

 

You'll need to determine what rear end gears you're running, then purchase the appropriate drive and/or driven gear(s).

The following company should have what you're looking for:

http://www.transmissioncenter.net/sp...n_______va.htm

JamesC