Join Date: Aug 2006
BlazingSaddle is offline
Re: Ring Gear Size???
Of course they are diffferent. one is an eigth of an inch bigger than the other. The 91 probably has the bigger one. Carrier is determined by axle ratio. yours is a 3.73 so you have the series 3 carrier. Yes the axles have different splines. They are not neccesarily related to the size of the gear. A 7.5 can be installed with 28 splined axles if the carrier or posi is right.
What you need to know most of all is wether or not your truck has EVER had anything done to the rear end. If you cannot be sure, start from scrtch by determining your gear ratio without looking at rpo codes. there are mothods turning the wheel while counting how many times the driveshaft turns is one way. One wheel blocked other off the ground. Please look for an accurate descrption on how to do this on the web elsewhere. It can be found and its not hard.
The gear ratio determines the carrier. The axle spline count, if NOT known for sure, is best found by pulling an axle. of course the axle is held in by clips inside the rear, so if pulling the cover anyway, its best to just count teeth on the gears while there to get the ratio.
The reason no-one can tell you for sure is simple. WE don't know your truck. The early models all had 7.5 and later they went to 7.625 the problem is that they also changed spline counts and while al the changing was going on not all trucks were built the same. there is also a number stamped on the rear. I believe its on the front of the drivers side. this code should tell you what was the ORIGINAL setup of the rear. Since many parts interchange, someone can fix a rear by installing parts from different vehicles inside the pumpkin.
No one knows where that pumpkin has been unless you do. If you find the number, which requires lots of looking and cleaning, and you know for sure it has never been out, you'll be sure of what it means. Otherwise, I am with everyone else and suggest pulling the cover, a clip and an axle.
Hey, if you drive it everyday, why not leave it alone?