Our Community is 940,000 Strong. Join Us.


GM 12-Bolt Advice Needed


Ol'Jim
05-31-2005, 02:32 PM
My bracket race car is a 71 Monte Carlo 408 BBC with T-400 & 12-Bolt Rear. Eaton Posi unit, with Richmond 4.10 gears. Heavy Car, (3750# without driver), fairly mild combo. (12.30 @ 108, 1.71 60').
Problem: Broke a Spider Gear (pinion Gear) last season, which trashed pretty much all internal differential parts. Replaced posi with identical unit, which was in very good condition. New R&P gears, bearings, etc.
10 races later, (72 passes), I was pulling routine maintenance, and Cross-shaft in Posi unit is severely galled, as are the spiders that ride on it. Had been using synthetic 75W90 oil for years, when I repaired it last year, Richmond suggested petroleum-based 85W140 instead. The cross-pin is very poorly lubricated, but this is incredible how bad it got chewed up, and how quickly! Okay, 3 questions:
1. What caused this rapid failure? Cross-shaft was "Yukon" brand - could be Chinese sh!t metal?? Or weak clutches in posi, causing single-spin?
2. I cannot get the cross-pin out, I beat on it for almost 2 hours, and it is halfway out of the housing. So I cannot remove the axles, or the carrier. Do I need a cutting torch to get this shaft out? Or?? Anyone had similar experience?
3. Pretty-much decided to go to a spool. I have some GM axles with C-Clip Eliminators on them. But no installation instructions. I am told I have to cut the ends off my axle-tubes? Anyone done this before, or have some instructions on what I need to do to use these? Looks like the bearing retainers are split in 2 halves, do I sandwich the backing-plate flange between the 2 bearing blocks?
Thanks in advance for your help.
-Jim.

500
05-31-2005, 08:13 PM
Get some aftermarket axles. You are turning a damn fast time for such a heavy dog. With the spool and the high weight the axles will be taking a beating any time you turn the steering wheel. The axle supplier will be able to suggest the best way to retain the axles.

Take a 1000 lbs off that thing and it will be a lot faster and easier on parts in the bargain. I had a 78 camaro that weighed 2600 lbs without the driver. The only fiberglass was the lift off hood. Windows rolled up and down. Stock windshield and back glass. 6 point roll bar.

Door guard beams 25+ lbs ea

Roof inner steel liner 35 lbs. ,etc.

Ran 12.63 best with a 4.88 [ way too low. 4.10 would have probably run 12.40 ] std bore 350, 600 holley, performer intake, cam dyn 228 @ .050 hyd, std cast flattops. 1.92 & 1.5 valves. Ported dbl humps. Hood scoop blocked off. Had to fight like crazy to slow it down to the 13.00 index.

Ol'Jim
06-01-2005, 09:00 AM
500 Thanks for the reply.
I do have Moser alloy replacement axles that are in the car now, I will have the C-Clip nubs ground off, and mount the C-Clip Eliminators on them. I am concerned that the elims will change the position of the axle flanges. Right now I have 10" wide wheels, 11" wide slicks, which have about an inch clearance on the inboard sides, and barely 1/2" outside clearance within the wheel opening of the 1/4 panel.
A friend is coming over today to cut the posi cross-shaft out with a torch so I can remove the axles & carrier.

blownS10blazer
07-09-2005, 04:41 PM
3. Pretty-much decided to go to a spool. I have some GM axles with C-Clip Eliminators on them. But no installation instructions. I am told I have to cut the ends off my axle-tubes? Anyone done this before, or have some instructions on what I need to do to use these? Looks like the bearing retainers are split in 2 halves, do I sandwich the backing-plate flange between the 2 bearing blocks?
Thanks in advance for your help.
-Jim.
I am in the process of installing c-clip eliminators on my 12 bolt truck axles and have already cut my housing tube ends. Not hard at all. I have instructions for both 12 bolt car and 12 bolt truck from Moser. If you want, send me an email and I'll email you the instructions.

Add your comment to this topic!