Gear Setup Question?

[02BLK_Limited]

Question for all of those out there that have successfully rebuilt your 8.8 rear end... I believe I already know the answer to my question, I will need to re-shim the pinion gear to bring it closer. However, in case I might be wrong - The two pictures are of drive and coast marks on a set of FRPP 4.10 gears with backlash set at .010 and pinion depth set matching original gears. Did not have access to pinion depth gauge and I'm doing this all in my garage. Do these patterns fall within the acceptable range by anyone with much experience building rear ends... or am I correct in assuming I need to re-shim. Thanks for your input!

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[Cobraguy]

Oh God no. That diff needs some work yet. Did you re-use the pinion shim from the old pinion? Ford to Ford normally works pretty well.

 

[IZwack]

Its hard to tell whats been marked with the yellow compound but it looks like you first need to put more on -- you need to paint a few teeth (of the ring gear) all the way from top to bottom and toe to heel. And then you can rotate the gearset to check for pattern.

But if you have marked the teeth properly with the marking compound and thats the pattern you get, then the gears need a bit more work.

The pattern is still "high" in the gearset below but once you've marked it from top to bottom, it should look something like this:

 

[02BLK_Limited]

Thanks for the replies - Didn't use shim from old pinion as I didn't have the correct tool to remove the old bearing from the pinion - I measured the old pinion, shim & bearing combo with a digital caliper and then measured the new and made them identical with shims.

I painted the whole surface of about 7-8 teeth, The paint you see in the picture is what the pinion gear picked up and re-deposited on other teeth. Pictures didn't come out well of the others. I was rotating the ring gear to produce resistance against the pinion which currently has 18 inch-pounds of preload.

Hindsight always being 20/20, I should have bolted the pinion up without the crush sleeve, using the old nut, to check this first.

Autozone / CSK don't seem to have bearing separators for rent - Anyone local in AZ that has one by chance?

 

[IZwack]

Well if the top image is the drive side of the teeth, then the two gears need to come together closer - the pinion needs to come "in" the differential housing more and the ring gear needs to move towards the pinion's rotational axis more.

But looking at the bottom image, is this gear set used? Because the inner tooth is beveled in such a way that kind of looks like its been abused or something. Maybe its just the gear manufacturer's standard but I have never seen that beveled inner corner on Yukons and stock gears sets.

 

[02BLK_Limited]

Brand new set of FRPP 4.10 gears with the part number ending in A (Actual ford product and not a Motive-made version)

This is the second set of these gears I've installed in the last year and they look identical to the first which I put in a friend's 2001 Mustang GT. I have a set of Motive 4.10 gears sitting in my garage which look quite different in terms of tooth shape and beveled edges. Seems that the design of the ford gears is what makes them silent compared to the others. Here is a picture of the other painted area.

Pictures of FRPP vs Motive gears

FRPP side view
Motive side view
OE Ford 3.55's showing beveled edge