Where exactly am I measuring the depth relative to? from the diff. case, the ring gear? what I'm trying to say is basically where do I put the base of the depth. micro and I'm guessing I put the rod on the top of the pinion gear right?

 

It depends on the exact tool you have... but one way or another, it measures the distance from the center of the carrier bearings to the back face of the pinion. It sets where along the diameter of the ring gear the pinion sits.

 

I've got a starrett mic with a 2 1/2" or 3" base and a number of rods up to 9" thanks for any help you can provide!!!

 

The spec on the distance that I gave you is something like 2.45" or some such IIRC.... if you're looking for a number like that, then it's from the center of the bearing saddle. If you have a spec that's in the 1" neighborhood, it's from the bottom of the bearing saddle to the back of the pinion.

 

cool, thanks for the info, we're putting in some 4:10 gears into a 10 bolt, so forgive me if im wrong but with that gear the ring should be smaller; calling for a thicker pinion shim to get the gears to mesh right?

 

Since you don't have "the tool", you can do one of two things...

Keep adjusting via contact pattern....

or

Measure the bearing race OD and divide by two...keep the number for reference.

lay drill rod where the carrier bearings sit.

measure from the bottom of the drill rod, to the top of the pinion gear.

add the above "OD/2" number you saved earlier.

Adjust pinion shim accordingly.

Should put you darn close...to within one or two shim changes.

Then again, you could read you manual, look at the pinion marking on the old gear...look at the pinion marking on the new gear...and set accordingly...assuming you can still see the depth marking and the new gear has one too

 

The ring is the same diameter in a given model of rear no matter what the ratio; 7½" in this case. That's why it's a 7½", or a 9", or a 8.2" rear.

The pinion will be smaller with a 4.10 than it would with a numerically lower ratio. But its back surface will ned to be in exactly the same place.

The factory did a pretty good job on the pinion bore machining on these housings. If you're using about any gear besides a Richmond, use a .035" shim behind the pinion bearing. If you're using Richmonds (which are cut differently), you have no choice but to look up the spec and measure it.

 

i use a depth mike with the 2-3 rod. i made a piece to act as a datum surface to measure from. all it amounts to is a piece of aluminum bar stock .5x1 inch (i think) with holes drilled in each end to bolt to the bearing cap surface. measure from it and subtract .5 from the reading for the datum thickness and you have your pinion depth. my part works for gm 12 bolts and both sizes of 10 bolts.

 

well, I got the whole rear disassembled today, the pinion is totally gone...... I mean theres nothing but a flat surface where the teeth were! The inner pinion bearing was pretty much dissentigrated...... totally ripped apart. diff. housing with a bunch of metal filings inside I'll try and get some pics tomorrow