Broke my R&P so I ordered a new set. Same ratio - 4.33 for 12 bolt.

Old pinion depth on gear is 2.566". New gear depth is 2.755"!

Maybe I'm missing something but I don't know how to remove what calculates to be .167"!
------------------Old--New
Pinion depth 2.566" -- 2.755"
Pinion thickness 1.908" -- 1.914"
Pinion shim .028" -- ?
Total 4.502" -- 4.669" + ?

Maybe this is not a fair way to look at it but it doesn't add up.

I don't have a depth checker, but this appears to be way off.

You need to check it with a depth checker, the face of the new pinion is probably thinner making it further from the carrier centerline...…..

Or stick a .030 shim in it, set the backlash look at the pattern and go from there.

Are you talking about the Check Distance marked on the gear?
Assuming same Mfr & P/N as your previous set, right?
I do not believe this is an issue to be concerned about, every set is unique.
As long as you are installing the matched set, which has been run-in together by the Mfr. the C/D is a reference point to get the same engagement depth of the pinion to ring gear as was used when they lapped them in together at the factory.
I recommend what The Bender said. Start with a .030, (honestly, this seems to get you in the ballpark most times). Install it correctly, check pattern, backlash, and shim as necessary.
BTW, for anyone working on 12-Bolt or Ford 8.8 stuff, I highly recommend using a solid spacer and shims, instead of a crush sleeve. Like this one from Just Differentials:
GM 12-Bolt Car Pinion Spacer & Shim Kit They are only around $30, and worth more than that in time saved and headaches avoided.
You can change pinion seals or yokes, and the preload never changes. And no more over-tightening the crush sleeve, and having to start over.

This message has been edited. Last edited by: FootbrakeJim,

quote:

Originally posted by "The Bender":
You need to check it with a depth checker, the face of the new pinion is probably thinner making it further from the carrier centerline...…..

New pinion is actually thicker. See chart above.

Nope, if the checking distance is a larger number on the new pinion that means the face of the pinion is further away from the carrier bearing centerline.

If you are measuring the "pinion thickness" the only meaningful measurement is from the bearing seat to the face of the pinion, where the pinion depth gauge would go. Just measuring the thickness of the gears is meaningless.

This message has been edited. Last edited by: "The Bender",

quote:

Originally posted by "The Bender":

If you are measuring the "pinion thickness" the only meaningful measurement is from the bearing seat to the face of the pinion, where the pinion depth gauge would go. Just measuring the thickness of the gears is meaningless.

Exactly. The "thickness" in above chart is the dimension from the bearing seat to the face of the pinion where the pinion depth gauge goes. The 2 pinions are only .006" different in "thickness" but .189" different in pinion depth spec (etched into the gear face). That .189" is causing my confusion. Thats 3/16" deeper in the housing. It just doesn't make sense.

I'm going to humor the number on the pinion. I went ahead and installed the bearing with the same .028" shim that came out and will see what it looks like. Ought to be interesting.

I would suspect that your pattern will look fine with the .028 pinion shim.

quote:

Originally posted by Brktracer:

quote:

Originally posted by "The Bender":

If you are measuring the "pinion thickness" the only meaningful measurement is from the bearing seat to the face of the pinion, where the pinion depth gauge would go. Just measuring the thickness of the gears is meaningless.

Exactly. The "thickness" in above chart is the dimension from the bearing seat to the face of the pinion where the pinion depth gauge goes. The 2 pinions are only .006" different in "thickness" but .189" different in pinion depth spec (etched into the gear face). That .189" is causing my confusion. Thats 3/16" deeper in the housing. It just doesn't make sense.

I'm going to humor the number on the pinion. I went ahead and installed the bearing with the same .028" shim that came out and will see what it looks like. Ought to be interesting.

Ok that clears it up. I just figured you were measuring just the gear thickness. It doesn't add up to be that much of a difference. Let us know how the pattern looks with the .028 shim.

Gears are installed. I ended up with .032" pinion shim. Backlash .005"

I was really disappointed with this gearset. The outter pinion bearing and the yoke fit were way too tight. I couldn't even get the yoke on enough to get the nut started with a big hammer and the gear on the floor, much less trying to put the pinion in the housing. The outter pinion bearing was the same way. It would have been necessary to press it on - not possible under the car. I had to do some polishing on the lathe and wire brushing on the splines to make them fit. It would've been impossible without a lathe.

Thanks for all the tips and advice!

One thing I noticed that surprised me. I've always heard that pro gears would wear excessively and would eventually need to be replaced for wear. The old gears have almost no wear after 10 years. The failure mode was a tooth completely ripped off the pinion. Most of the other pinion teeth are cracked. Ring gear looks fine.

Thanks again!

This message has been edited. Last edited by: Brktracer,

Matt, do you mind telling the gear brand?

Curtis

Maybe not the technically correct wat.. I have never worried too much about measurements as long as drive and coast patterns are correct at backlash I want then I ran them.End results. Dozens of rear ends over the years and none had issues. Might save some time with measurements I guess.