12 Bolt Chevy problem

Kingpen · 08-02-2009, 09:56 PM

Ive been fighting a problem with keeping pinion shims from coming apart & out.car is a 95 camaro stocker but I run it in SS with SS motor.weighs 3400lbs with p/g & 99% of the time it is foot braked.it has a Strange housing ,which I figured would be better for making things last longer,but after 50-60 runs,it will start making noise & when I check,the shim is gone.this has happened 3 times in the last 2 years.I use the ratech collar instead of crush sleeve and always get pinion depth within .003-.004 of what is written on gear.Pinion nut is still "tight" from the loctite but of course has some slack from the lack of shim.The nut backing off doesnt seem to be the trouble as I have marked it before to see if that was the case.any ideas,suggestions(dont want to change housings),something I am missing???got lucky this time and didnt hurt gears,not so in the past....let me know............thanks Vic Penrod

Duane Eiskant II · 08-02-2009, 10:38 PM

Vic what rear end cover are you using? Not sure if its the problem or not but you should use a cover like the one T/A sells. Moser does also (think T/A makes them for them). Ive heard stories about the 12 bolts where the main caps actually "flex" on the launch. Maybe its flexing causing things to beat around in the pinion?????just a guess, something worth looking at maybe.

Mark Yacavone · 08-03-2009, 01:04 AM

I don't know what's causing the problem, but why don't you put a shim under the bearing race, like on a Dana?

Bob Bender · 08-03-2009, 03:28 AM

Quote:

Originally Posted by Mark Yacavone

I don't know what's causing the problem, but why don't you put a shim under the bearing race, like on a Dana?

Thats what I do in my 12 Bolt

Danny Ashley · 08-03-2009, 06:19 AM

Sounds like not enough pre-load on the pinion. How much do have on inital set-up? I've always set mine 15-17 inch pounds. I see where Ratech now has a "Smart Sleeve" that you may want to try instead of the solid spacer. Good luck. Danny

Alan Roehrich · 08-03-2009, 06:20 AM

Never had a good pinion shim fail, unless the pinion nut is backing off, or not tight enough to begin with. It is also possible that the bearings are not getting enough preload. Ordinarily, it will kill the shims on the spacer before it hurts the shim on the pinion bearing.

Bob Mulry · 08-03-2009, 06:42 AM

You're not honing the forward pinion bearing to make it easier to set up the pinion depth??

Are you???

Bob

Jim Kaekel · 08-03-2009, 08:24 AM

Mark is correct. I had similar problems years ago with mine, shims getting damaged, but the Ratech severe duty pinion shim kit #1901 solved the problem. Kit relocates shims between the housing and the race.

Ed Wright · 08-03-2009, 09:22 AM

Guess I have been lucky. I've never had that happen. I think you need to get closer with your pinion depth, but that won't effect the shim problem. I have broken teeth on one ring gear, and found them cracked on another a few weeks back, but my shims have always lived. That's a new one for me.

08-03-2009, 09:27 AM

Thats what I'm thinking Bob, The pinion bearing still needs to be a press fit. If not the bearing will spin, even with a Ratec solid collar. Alot of racers hone the bearing so they can change gears or repair at the track.This may work at time but not all the time. I'd use a new bearing or if the pinion was sanded some loctite sleeve retainer on it. That should help your problem...

Quote:

Originally Posted by Bob Mulry

You're not honing the forward pinion bearing to make it easier to set up the pinion depth??

Are you???

Bob

08-02-2009, 10:38 PM	#2
Duane Eiskant II Senior Member Join Date: Dec 2001 Location: Alexandria, Va Posts: 501 Likes: 261 Liked 57 Times in 33 Posts	Re: 12 Bolt Chevy problem Vic what rear end cover are you using? Not sure if its the problem or not but you should use a cover like the one T/A sells. Moser does also (think T/A makes them for them). Ive heard stories about the 12 bolts where the main caps actually "flex" on the launch. Maybe its flexing causing things to beat around in the pinion?????just a guess, something worth looking at maybe. __________________ Duane Eiskant 1354 Stock/Super Stock

08-03-2009, 01:04 AM	#3
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,809 Likes: 2,900 Liked 5,114 Times in 1,948 Posts	Re: 12 Bolt Chevy problem I don't know what's causing the problem, but why don't you put a shim under the bearing race, like on a Dana? __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

08-03-2009, 06:19 AM	#5
Danny Ashley Member Join Date: Nov 2001 Location: Marion,In. Posts: 267 Likes: 60 Liked 110 Times in 29 Posts	Re: 12 Bolt Chevy problem Sounds like not enough pre-load on the pinion. How much do have on inital set-up? I've always set mine 15-17 inch pounds. I see where Ratech now has a "Smart Sleeve" that you may want to try instead of the solid spacer. Good luck. Danny

08-03-2009, 06:20 AM	#6
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,105 Likes: 1,564 Liked 1,789 Times in 408 Posts	Re: 12 Bolt Chevy problem Never had a good pinion shim fail, unless the pinion nut is backing off, or not tight enough to begin with. It is also possible that the bearings are not getting enough preload. Ordinarily, it will kill the shims on the spacer before it hurts the shim on the pinion bearing. __________________ Alan Roehrich 212A G/S

08-03-2009, 06:42 AM	#7
Bob Mulry VIP Member Join Date: Apr 2002 Location: Coarsegold, CA Posts: 1,016 Likes: 57 Liked 320 Times in 102 Posts	Re: 12 Bolt Chevy problem You're not honing the forward pinion bearing to make it easier to set up the pinion depth?? Are you??? Bob __________________ Bob Mulry 7516 STK A & M Motorsports

08-02-2009, 09:56 PM	#1
Kingpen Member Join Date: Feb 2006 Location: sooner state Posts: 105 Likes: 3 Liked 64 Times in 22 Posts	12 Bolt Chevy problem Ive been fighting a problem with keeping pinion shims from coming apart & out.car is a 95 camaro stocker but I run it in SS with SS motor.weighs 3400lbs with p/g & 99% of the time it is foot braked.it has a Strange housing ,which I figured would be better for making things last longer,but after 50-60 runs,it will start making noise & when I check,the shim is gone.this has happened 3 times in the last 2 years.I use the ratech collar instead of crush sleeve and always get pinion depth within .003-.004 of what is written on gear.Pinion nut is still "tight" from the loctite but of course has some slack from the lack of shim.The nut backing off doesnt seem to be the trouble as I have marked it before to see if that was the case.any ideas,suggestions(dont want to change housings),something I am missing???got lucky this time and didnt hurt gears,not so in the past....let me know............thanks Vic Penrod

08-03-2009, 08:24 AM	#8
Jim Kaekel VIP Member Join Date: Jul 2002 Location: Michigan Posts: 1,227 Likes: 133 Liked 530 Times in 108 Posts	Re: 12 Bolt Chevy problem Mark is correct. I had similar problems years ago with mine, shims getting damaged, but the Ratech severe duty pinion shim kit #1901 solved the problem. Kit relocates shims between the housing and the race. __________________ Jim Kaekel 3836 STK

08-03-2009, 09:22 AM	#9
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: 12 Bolt Chevy problem Guess I have been lucky. I've never had that happen. I think you need to get closer with your pinion depth, but that won't effect the shim problem. I have broken teeth on one ring gear, and found them cracked on another a few weeks back, but my shims have always lived. That's a new one for me. __________________ Ed Wright 4156 SS/JA Last edited by Ed Wright; 08-03-2009 at 05:16 PM. Reason: Spelliing