My shop that is doing the work on my rear diff said that my surfaces are out of plane.
They said something like 4 thousandths. I told them to proceed with the install and just average the values when they install the pinion. It's not like I'm running slicks and racing. The current rear has 148K on it and it didn't show any serious wear.
I've never heard of this before so can somebody tell me that this is a common problem with a 3.08 open diff 7.65" rear.
Thanks

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, Jon (350 TBI!)
91 Red My website

 

it would be the parting surface where the bearing caps bolt up to. i'm sure they're machined as a pair in one set up on a mill. what has happened is something has moved and they are no longer on the same plane, or out of flat by .004. when i set up a pinion i use a piece of aluminum as a datum surface extended across the bearing caps. depending where on the pinion you measure the depth at you might be off .0015 or so from side to side. it may distort back in your favor too as the caps are torqued down. i run a girddle on my rears and that could also help bring it back to spec. i wonder how and with what he figured out the surfaces were out?

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

He has a pretty trick looking tool. It's completely machined and he cleans off the surface where the caps bolt up to. It has an angle which brings an "arm" piece to any of the other 3 surfaces. Everytime they measure it's always off. They've recalibrated the darn thing and still off. I hope it'll be okay. He said if it were his car he would go ahead and do the swap and check it a couple weeks later. So that's what's being done. Hopefully this doesn't break any of my ALL NEW PARTS!!! I spend a good $350 in parts alone.

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, Jon (350 TBI!)
91 Red My website

 

He has a pretty trick looking tool. It's completely machined and he cleans off the surface where the caps bolt up to. It has an angle which brings an "arm" piece to any of the other 3 surfaces. Everytime they measure it's always off. They've recalibrated the darn thing and still off. I hope it'll be okay. He said if it were his car he would go ahead and do the swap and check it a couple weeks later. So that's what's being done. Hopefully this doesn't break any of my ALL NEW PARTS!!! I spend a good $350 in parts alone.

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, Jon (350 TBI!)
91 Red My website

 

That sounds like the same setup as the pinion depth gage from Precision Measument. I have used it before and it is very inconsistent.

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
Currently installing 3.73's into my 9 bolt (YES,it is a 9 bolt & YES they are 3.73's, not 3.70. 4.11's to follow soon )
www.koolmeister.com

 

New problem! They can't do the gear swap.
The Richmond gears aren't going in as expected. The pinion gear is shimmed beyond max recommended and still the gears don't meshup. The gears are only showing 5/8" of actual surface touching (don't know how else to explane it). I know it needs at least an inch of the rear won't make it more than 50 miles down the road. The shop guys think it's the gears that are bad.
A good friend of mine has a 12 bolt in his 69 and he said that his bearing cap surfaces were off just a bit and that he used a piece of aluminum to measure pinion depth. He also said that the pinion depth should have a mark on it to tell you the depth it should be set too and left alone. Then set the backlash, I don't know what that is. Can somebody please tell me what the **** they would do if they were in my shoes. BTW, I got the gears from a guy online. He's a thirdgen member and a good guy. He got them at some show where he won them and has no use for them. Either the shop guys don't know what they're doing or....the gears are fubar or.... my 10 bolt case carrier is fubar.

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, Jon (350 TBI!)
91 Red My website

 

the pinion setting depth is etched on the bach of the pinion. i set it with a depth mike. the back lash is etched on the ring gear, set it with a dial indicator. check bearing preload with a dial type inch pound torque wrench. i've never heard of a pinion needing more that .035 or so in shims. i wonder if you have the right series gear set for your rear end houseing.

 

It sounds like you may have the wrong series gearset or carrier, a non matched set of gears(check the mating numbers) or the shop has no idea what they are doing. Has anyone heard of a way to determine if the bearing cap surfaces are all on the same plane? I have never even heard of such a procedure as part of a gear install.

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter