I'm getting ready to order a 145 mph speedo. The previous one I had was a 110. I had my tires replace when I got the car, from some little teeny lowrider lookin ones. THis made my speedometer 7-10mph off. What do I need to do to fix this? Then when I switch speedo's, is there anything I need to do or will the computer know that its a 145 and not 110?

 

89 camaros still have mechanical speedos, if its stock. What needs to be changed to correct for a different tire height is the drive/driven gear set in the tranny tailshaft. If its a 145mph speedo out of another 86-89 camaro it should just plug right in to the cluster, hook up the cable and go.

 

Try here

http://www.700r4.com/SpeedOCalc/

 

How hard/what do I have to do to change that gear set? Doesn't look too expensive.

 

changing the driven gear is extremely easy. one bolt, unplug the housing swap gears, smear some silicone, plug back in and bolt up....the drive gear is inside the tailshaft, and I've never had to do it, so I cant say for sure.

 

Yeah watch out when you pull that driven gear out, tranny fluid will flow out like a fountain. Now I don't know if only changing the driven gear will help. You might want to see if you have to change the drive gear cause that is a whole another problem. That is inside the transmission and I assume a rather long job. I got a 145mph speedo on my car from e-bay from a guy who had it new and in the stock box from GM. I didn't have different wheel sizes though or wheels so it just plugged right in.