Rear Diff - Crush Collar Question - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 01-01-2016, 08:26 PM Thread Starter
 
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Rear Diff - Crush Collar Question

Hi,

I recently had the gears in my 12 bolt rear switched from 3.73 to 3.42 and the shop that did the work told me that I should drive 5 or so miles and then tighten the pinion nut which in turn would compress the crush collar.

Does anyone have any experience with this? Why should I have to drive it 5 miles and then tighten? How tight should I make it in torque pounds? The shop said I could bring it back and they would do it but I would rather do the work myself. Thanks.
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post #2 of 5 (permalink) Old 01-01-2016, 09:47 PM
 
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What the shop told you speaks volumes about their knowledge in properly setting up ring and pinions. to put it mildly, they are !d!ots. I would suggest flatbedding the car out of there on a wrecker and get the rear to someone very well versed in building differentials. Good chance the pinion depth is off, the installer, is winging it, anyone can set backlash with a pile of side shims. unfortunately there are a ton of "wing it" types out there. Their installs do nothing but add to shorted R & P and bearing life.

Proper build procedures. Once correct pinion depth is determined and backlash is set, and the R & P has a great pattern (with considerable drag applied to the pinion flange), the builder will disassemble. Then and only then, install the crushsleeve. I usually use two pinion washers in the initial phase and a new pinion nut that has JT6 lube on it, i dont want to risk galling the threads or running the new pinion nut all the way onto the pinion. During final assembly as I approach the pinion flange being seated, still no drag, I will remove the only partially threaded new pinion nut, both washers, a thoroughly clean with solvent the threads on the pinion and the pinion nut, then reinstall one pinion washer, the new nut, and put blue Lotite on the pinion nut threads. Then will carefully tighten, eventually recreating 15 inch lbs as my dial indicator on the pinion depth tool indicates the exact correct number for correct pinion depth. After reinstalling the carrier and again setting backlash with a combination of the correct thickness cast spacer on the lh side, and a service spacer and correct shim on the right hand side, will then reapply drag to the pinion flange, and ck the pattern. Last, will take a small blunt chisel and make three marks around the edge of the pinion nut in order to "stake" it. The combination of the loctite, and the staking will keep the pinion flange from loosening. you don't want the pinion nut loosening, will end up getting abnormal wear.
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post #3 of 5 (permalink) Old 01-02-2016, 07:42 AM Thread Starter
 
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Thanks PH, not quite what I wanted to hear but you speak from experience. This sucks, I was hoping it wouldn't be this complicated. I am curious about how many inch pounds were already applied to the pinion nut. If it was done incorrectly, could I tell right away (I have not driven the car since the gears were installed, the rear diff was out)
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post #4 of 5 (permalink) Old 01-06-2016, 11:38 AM
 
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Garage
The pinion nut should be set and the collar 'crushed' at the time the gears are installed, shimmed and set up....Gotta agree with PINION HEAD....



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post #5 of 5 (permalink) Old 01-06-2016, 11:42 AM
 
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Quote:
Originally Posted by TonysGoat View Post
Thanks PH, not quite what I wanted to hear but you speak from experience. This sucks, I was hoping it wouldn't be this complicated. I am curious about how many inch pounds were already applied to the pinion nut. If it was done incorrectly, could I tell right away (I have not driven the car since the gears were installed, the rear diff was out)
You could tell if the rearend was opened and the teeth checked for proper install....if you have NOT driven the car...DON"T....take it to a good rear end shop...you will probably need to have the rear checked, possibly shimmed ..and a new crush collar properly installed (they are usually considered a "one shot deal"...some people will say that is is OK to tighten the pinion nut, as this crushes the collar more....but not to LOOSEN it.....Personally, I like a new one each time !!!!!!!!!



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