I did a search and didnt find much on this. I have a 89 Firebird and I just did a rearend swap from the 10 bolt with 2.73 gears to a 12 bolt with 4.11 gears. And of course now my speedo is way off. It reads about 35 miles per hour too high(if I am doing 60 it reads 95.) My question is what do I need to do to calibrate my speedo??


Thanks in advance for any help.

Usually you'd change the speedometer gears in the transmission. Although with 4.11s there isn't a combination of speedo gears that will work, you'd probably need an external ratio adapter as well.

Thanks for your input Apeiron!