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

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.

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?

Re: 12 Bolt Chevy problem
 

Thats what I do in my 12 Bolt

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

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.

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

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.

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.

Re: 12 Bolt Chevy problem
 

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...

Re: 12 Bolt Chevy problem
 

Vic. You have a PM.

Re: 12 Bolt Chevy problem
 

some really good points that you sometimes overlook because you get tired of looking..yes I have a good cover/girdle,but yes I am also guilty of sanding the pinion gear for easier removal.my other car has a dana 60 that has all that stuff & never had problems ,but shim is also behind the race too.I will try that with the 12-bolt & see.as far as pre-load,Ive never measured it,just went by feel,and have used from "snug" to "tight",,I probably should actually measure it....as far as the pinion to bearing fit,I have some Green sleeve retaining loctite,will this help,plus maybe some carefully placed light center punches work to hold it in place?..I really appreciate all the answers & suggestions,if there are any more,I'll gladley listen as it will still be a couple of days before i start back toegther with it...........Thanks so much,Vic.......P.S. I also have some converter questions I'll ask in another thread if anyone wants to help

Re: 12 Bolt Chevy problem
 

Vic, we have run twelve bolts for years with high horsepower engines etc. I set up the gears and have a lot of experience and proper tools to get it done. I machined billet heavy duty caps for the spool bearings,
made my own solid design pinion spacer that used a shim along with front and rear holes to allow gear lube to flow thru machined tubular spacer. The spacer seemed to always show signs of loosness when tore down. MY Fix, pinion has ran five years now with no spacer between the bearings. If you want to try this always use a new G.M.pinion nut with heavy duty loctite, tighten nut to intended pinion preload and let set a day or two before running the car for loctite to harden. I use a 40 inch pound torque wrench to
set the preload, it was designed to set the preload on jet engines and was military surplus when I bought it
Good luck on fixing the problem, Ray

Re: 12 Bolt Chevy problem
 

V ic,

Give me a call at 650 922 0407


Bob

Re: 12 Bolt Chevy problem
 

on the "sanded bearing" idea...i have a used but in good shape bearing that is polished (sanded) to be able to tap it on and off for setting the pinion preload and clearance, then once the proper shims are selected i remove the bearing and install a new one. bearings have a high tolerance from one to the next, as long as you use the same manufactuer and p.n. each time you shouldn't run into clearance changes.

Ian