i just recently got my mustang and the guy told me it had 3.73's but i think its that low. it does about 1700-1800 at 60mph. is that right for 3.73's? thanks brandon

 

its a 5spd car by the way

 

It doesn't read like a 3.73, more like a 3.08. Anyway...if you want to be sure, use this calculator link to figure out which gear is really installed. Hope this helps.

 

It sounds like you have lower gears. My car w/ 3.73s runs at about 2000-2100 at 60 mph. A lower gear will mean lower rpms at a cruising speed like that.

 

your gonna have to do it the hard way, since you don't what gear, you don't know what the correct speedo gear combo is to make sure your mph is correct.

you'll need to count the rotations of the wheel to the rotations of the DS.

raise the backend , and chalk the tire, and DS......

1 complete revolution of the tire , and count the spins of the DS

3 1/2 = 3.55
3 3/4=3.73
etc.

if you have a '86 t5, it has a 7t drive gear for the speedo (the one in the tailshaft) and you need a 21t speedo driven gear (the one on the end of the speedo cable) for it to read correctly.