Originally Posted by 39chevy
what gm w/3.73 running gear measurement backing plate to backing plate 56 inches, 1/2 inch eather way? thanks, Dana
What is wrong with the one you have?
If you are getting a loud clunk when shifting from reverse to drive or get wining you are better off just replacing the gear set. If you want while you have the differental out just go ahead and replace the diff as well. You can upgrade to a POSI unit (clutch type) or go to a gear type like Eatons Detroit locker (no it's not a locked drag race spool) or a Torison just is a little more. Both are a gear type Posi so they don't have clutches to chatter or wear out and you do not need to add the posi additive that clutch type need to work correctly. There is no adjustments needed and work great on the street. For an additional amount you can get a kit that has ever bearing, bearing race, seals and rear cover gaskets. Every thing to rebuild your rear in one box. It even comes with a short acid brush and a little tube of gear mesh compound to use to set up the pinion/ ring gear.
To have this done runs around $1500 - $2000. The only additional money would be for pressing the pinion bearing on after you put the correct thickness of shims on the pinion gear. Have the old pinion gear bearing removed and sand the inside enough to allow the bearing to go on the new pinion snug, that way you can change the shims without having the new bearing pressed on and off 4 or 5 time (it will take at least 4 trys to get the shim thickness correct unless your real lucky or you have the tool which you can buy from summit racing).
The tool I just mentioned measures the distance from the center of the axle tube to the face of the pinion. That measurement is scribed into the face of the pinion gear and makes the set up way easyer than the old way of having to use a dial gauge on a magnetic base and a special tool to find the center of the axle tube. This you just slide a few shims onto the pinion then slide on the old bearing you opened up, put the pinion in the housing then put the tool in the axle tube, when you have to correct slim thickness the gauge tool will be aganist the face of the pinion with no play. It makes setting the pinion depth a lot easyer.