• Registered: 2009-08-28
  • Posts: 606

Topic: GM differential issue??

Hey guys I'm looking for some input on something I have never had happen before.

We tore down the diff on our Camaro (GM 10 bolt)  to do a rebuild, fresh bearings, seals, etc...

When it came time to put the carrier back in the thing I could not get enough torque on one of the carrier bolts.

I typically criss cross the cap bolts and walk up the torque in steps...20 foot...40 foot...and so forth.   When it was time for the final pass at 60 one of the bolts just DID NOT want to make my toque wrench click.   I was pulling so damn hard my brain was telling my arm to STOP before something broke.   I spun the bolt out, checked the threads, looked down in the hole, everything looked fine.   I pulled both caps off, gave the bearings all a tap with a block of wood to make sure they were seated, again all was fine.  So I started again, and had the same issue again.  I got all 4 bolts up to 50 foot pounds, but as soon as I tried to do 60 the same bolt would not click. 

At this point I decided NOT to break anything and we put the rest of it together, filled it up with sluid, and spun the wheels in the air up to about 80MPH.   No issue, no noise, so at this point I think we are good.

What do you guys and gals think??   Is there a booger on the diff or the bolt that I'm not seeing??  Am I making a fuss over nothing??  Are the torques not the critical with a diff like this?? 

Input and ideas please!

Matt rat

Team Sucker Punch: Winner Class B Doing Time at Joliet 2023 Autobahn ,Winner Org Choice award Were the Elite Meet to Cheat 2015
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  • From: Pepperell MA
  • Registered: 2009-12-06
  • Posts: 536

Re: GM differential issue??

Maybe the torque wrench has a "bad spot" at 60 lbs?  Clamp the tip of the wrench in a vise and see if it clicks at 60 there maybe?  The diff covers with the support bolts do work IIRC so you might try and score a used one for a little insurance if you don't already have one.

Of course I have the diff of my daily driver '96 Z28 in pieces as I type to replace the ring and pinion and all the bearings.  I really didn't want to hear that the bolts might be one time use.  ARP sells a stud kit for those bolts too I think.

Nick
Focke Ewe racing -> Muttonheads! Racing -> Torque Junkies
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  • From: SF Bay Area
  • Registered: 2012-01-06
  • Posts: 721

Re: GM differential issue??

Typically, those bolts are not one-time use.
From the original post it is unclear if the wrench continued to turn, but not click at 60 lb/ft,
or if you could not apply enough torque to make it click. I tend to infer the former rather than the latter.
If that is the case, you have surpassed the bolt's elastic fatigue point, and it is stretching like a rubber band.
If you were to continue to turn the bolt it would stretch, and finally break. If you remove the bolt, you might
find that it was "longer" than the bolts that did reach 60 lb/ft.

Load them hard enough and the cap will move causing a misalignment with the ring and pinion.
Who knows if that will happen if you aren't launching hard with slicks.

Capt. Delinquent Racing
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  • Registered: 2009-08-28
  • Posts: 606

Re: GM differential issue??

DelinquentRacer wrote:

Typically, those bolts are not one-time use.
From the original post it is unclear if the wrench continued to turn, but not click at 60 lb/ft,
or if you could not apply enough torque to make it click. I tend to infer the former rather than the latter.
If that is the case, you have surpassed the bolt's elastic fatigue point, and it is stretching like a rubber band.
If you were to continue to turn the bolt it would stretch, and finally break. If you remove the bolt, you might
find that it was "longer" than the bolts that did reach 60 lb/ft.

Load them hard enough and the cap will move causing a misalignment with the ring and pinion.
Who knows if that will happen if you aren't launching hard with slicks.

I was pulling a lot harder ( I felt) on that bolt then all his buddies and I STOPPED before it stripped/broke/etc.

The thing is tight, that's for sure, I just don't think its clamping as hard as all of his buddies, it ATLEAST has 50 foot pounds on it, I got a click at that level.  The more I think about this the more I think that ten foot pounds isnt that big a deal, since like you said no slicks and no hard launches.   But....this is a Lemons F body, so maybe it IS a concern...dunno.

Team Sucker Punch: Winner Class B Doing Time at Joliet 2023 Autobahn ,Winner Org Choice award Were the Elite Meet to Cheat 2015
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Chevy Corvette 1984......and still racing!
  • Dave
  • Dave
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  • From: PGH PA
  • Registered: 2009-10-09
  • Posts: 993

Re: GM differential issue??

I would get a new bolt.

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  • From: WPB Fl.
  • Registered: 2010-10-27
  • Posts: 1,571

Re: GM differential issue??

Is your angle of attack different for that location? You may be binding the wrench, no clicky.. Place the bolt in a different hole, re-torque all to see if the issue still exists in the same place.

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  • From: Southington, CT
  • Registered: 2009-07-13
  • Posts: 94

Re: GM differential issue??

You are over-torquing the bolt for it's strength and the metal is deforming.  It is likely that it is not noticeable through visual inspection but what you describe is spot on to the feeling of a bolt in plastic deformation.  It could be that the torque spec. is for a dry bolt and yours are covered in oil or it could be that the bolts were over-stressed and no longer as strong as they were.  I would definitely get new bolts and probably get ARP.  Best of luck!

Sam

Rusty Tear Racing "Rally" Fiero
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  • Registered: 2009-08-28
  • Posts: 606

Re: GM differential issue??

Well folks I took care of the problem today.  I popped the diff open and installed a longer grade 8 bolt from the hardware store...and I got my 60 foot pound click. 

Still not sure what was up with it, but my guess is that the bolt just gave its notice after a few decades of hard work.  I have an ARP stud kit on order to be installed this winter.

Thanks for the advice everyone.

Team Sucker Punch: Winner Class B Doing Time at Joliet 2023 Autobahn ,Winner Org Choice award Were the Elite Meet to Cheat 2015
Chevy Camaro (Tiger striped #38)  (1989-2017 RIP old friend)
Chevy Corvette 1984......and still racing!