Pinion pattern

[jdalexa84]

I am installing a used gear set and carrier into my truck. Can someone tell me if my pinion is to deep. I am at .007 backlash and 16 in/lbs pinion preload on new bearings. Any help is greatly appreciated

[Eddie H.]

It looks too deep to me. I always try to set the contact pattern as close to the center of the tooth as I can .

[jdalexa84]

That is what I was thinking. I started with the factory shim. Thanks

[clinebarger]

Pinion Gear is too close to the Ring Gear, Reduce the thickness of the Pinion Shim.

If possible, Retrieve the Pinion Shim from the Original Pinion Gear, If thinner than the shim you are using now....Start with that thickness.

Most Corporate Cases are married to a Pinion Shim thickness When using OEM quality gears & Bearings.

Contact patterns for 2 & 5 Cut Gears http://www.demandaam.com/technical-s...ng-pinion-sets, If this is a 40 year old Gear Set I would guess 2 cut?

My 7.625" Diff in my Camaro, Using a Thick 3-series gear set & a 2-series Posi Carrier using the factory Pinion Shim to the case.

[jdalexa84]

Its out of a 80s blazer.

[Ironangel]

Originally Posted by jdalexa84

Its out of a mid 80s truck.

Pinon is to close to the ring. You can take .005" of shim(s) out of the left side carrier shim pack and reinstall them in the right side carrier shim pack to move the ring gear away from the pinion to gain clearance. Your backlash and preload are good, you just need to either install a thinner pinion shim or offset the ring gear carrier, I'm guessing .005"?...My 12T had a .027" pinon shim on it, the factory spec was .030"...I actually had to go back and install a .025" shim in order to get the preload and backlash to spec after installing a new posi carrier with new gears and bearings. You really need the shim that was on that pinon or at least know what was on it? I'm also wondering how much is on it now? Your close, thats the good news! Setting up a differential takes patience and if it's a 12-bolt, one or two extra crush sleeves takes the pain out of pulling a fresh installed pinion gear... ~Ghostrider~ PS. GM dropped production of the Truck 12-Bolt at the end of the 81 production run...Might not hurt to check the pinion thickness from bearing surface to the top of the gear head. My pinons were the same thickness but the new 3:73 pinion has a machined radius that required a slightly larger ID machined out of the factory pinon shim...

[jdalexa84]

It has the pinion shim that was originally on my truck before. I think it did look like the inside diameter was a little small

[mredd]

Originally Posted by jdalexa84

It has the pinion shim that was originally on my truck before. I think it did look like the inside diameter was a little small

You are assuming that the pinion gears are the same and that they are interchangeable without changing the shims. They aren't interchangeable. Each and every time you swap them out you must re-shim them. Set Pinion depth first then set backlash until the pattern looks like this:

[clinebarger]

Originally Posted by mredd

You are assuming that the pinion gears are the same and that they are interchangeable without changing the shims. They aren't interchangeable. Each and every time you swap them out you must re-shim them. Set Pinion depth first then set backlash until the pattern looks like this:

Sorry, Not true, I set-up 60-70 Gear-sets a year, 9 times out of 10....Corporate differentials go right together using the original Pinion Shim. Pretending that quality gears are being used of course. Set-up a '82 8.5" last week, Went from 3.08's to 4.11's....Perfect with the original shim.

Your guessing everyone has a Pinion depth tool, Probably not! I have one & hardly ever use it, Unless its a Dana.

[jdalexa84]

Everything I read says start with original pinion shim and adjust from there. Thats what I did. And since I have no experience doing this I mostly wanted to confirm what I was thinking as far as movement direction of the pinion. I have new shims to install so based on what I gather from the replies here I should lose about .005 to start and check again?

[clinebarger]

Originally Posted by jdalexa84

Everything I read says start with original pinion shim and adjust from there. Thats what I did. And since I have no experience doing this I mostly wanted to confirm what I was thinking as far as movement direction of the pinion. I have new shims to install so based on what I gather from the replies here I should lose about .005 to start and check again?

Yep, Start there, TIP.....Do not install the Crush Sleeve or Pinion Seal 'til your happy with the Pattern. Torque the Pinion Nut 'til the Rotational Torque is achieved.

[jdalexa84]

I bought a solid pinion spacer because I didnt want to mess up with the crush sleeve. I dont have anything in there right now. Im doing this under the truck in my brothers driveway hoping to get it done soon, snow will be here soon and I definitely dont want to do this in the snow lol. Thanks for the help.

[Ironangel]

Originally Posted by jdalexa84

Everything I read says start with original pinion shim and adjust from there. Thats what I did. And since I have no experience doing this I mostly wanted to confirm what I was thinking as far as movement direction of the pinion. I have new shims to install so based on what I gather from the replies here I should lose about .005 to start and check again?

Yes, your doing fine. Dont know who that other cat is but with a suspended account and only 3 posts I wouldnt hold much stock in his comment. When you go to take the pattern reading, try to apply some resistance to the rotating carrier with a gloved hand or a rag so that a good wipe of the pattern grease occurs Heres a page out of Randy Lyman's Differential Manual on reading tooth patters. And heres my final on the 12T I did a few months ago.

[cg285]

Originally Posted by clinebarger

9 times out of 10....Corporate differentials go right together using the original Pinion Shim. Pretending that quality gears are being used of course.

+1 - except i've always used oem gear sets/bearings. can't vouch for aftermarket sets.

[marvgarr68]

I will vouch for this also. I was setting up a 9.5 a month ago and used the stock shim on the pinion and same starter shims on the carrier. The gears were 5 cuts and I thought the pattern was fine in the center but a deceiving pattern. The old guys here said it was wrong and changed shims all around for two days. The end result was I put the factory shim in and it was good like I thought in the first place.