I need to calibrate my speedometer for my new 4.56 rear. The car is an 88 iroc z that had a 2.77 rear and 700R4 tranny. My question is in regards to the gear. Is their enough room on this to add enough teeth to handle the difference in rear, or do I need to get a reducer(new gear/adapter)? Any help would be greatly appreciated. Thanks Dennis

In the 700R4 there are two gears that are used to calibrate your speedometer. There is a drive gear and a driven gear. The drive gear is on the tailshaft of the tranny and the driven gear can be accessed on the side of the tranny where the speedo cable connects. These gears are all uniquely colored based on the the number of teeth on them. If you go into a chevy dealership and tell them the following information:

1) Tranny
2) Gear ratio
3) Wheel diameter and tire size

they should be able to give you the part numbers/colors for the two gears you need.

Jory

You'll need an adapter, there's no combination that will accomodate a 4.56 rear. You're pretty much out of luck with anything lower than 3.73.