Hey guys I've got 2:73 rear end and am going to get 3:42s.

Do you need to recalibrate the speedometer when you get them? Or is that included if you have the gears installed by a shop? If it's not how do you do it, if at all and more importantly how much? Been searching all day for this question.

 

As far as I know, you have to get your PCM tuned for the new gears to set your speedo right.

 

Tell us the specifics of your car.... year, model, engine, etc. Without that basic info, no one can answer your question accurately.

 

Sorry, its a 02 Trans am a4. What do you need to buy to change the CPU settings.

 

Yes, you do need to re-calibrate your speedo for 3.42s. Are you going to a rearend/differential shop...if so, they probably won't do the computer work for you. If you're going to an all around performance shop, they probably have the capabilities.

You have a few choices:

1. Buy a programmer and re-do speedo yourself. ~$300 for programmer.
2. Send out for a mail order tune and specifiy you want to calibrate speedo for 3.42s. ~$125 for mail order.
3. Find a local place that dyno tunes your car. They can re-program it as well. ~$100.

Prices above are just estimates to give you a ballpark range.

It would help if you told people that city/state you lived in....the locals on this board could help you find a shop near you.