Don't Reuse Rear Differential Cover Bolts????

[Dave in Mpls]

Was watching one of the games yesterday with a buddy of mine and the topic of conversation quickly turned to trucks (go figure!). I mentioned that one of the things I have left to do on my '04 'Burb was change the rear differential fluid. Knowing I had the gasket, he asked if I had picked up new cover bolts. WTF?? He knows his way around GM trucks a whole lot more than I do, and said that he had read in a service manual somewhere, sometime, that the cover bolts should be replaced, not reused. I'm not saying that is not the case, but that is the FIRST that I've ever heard of that! Can anybody verify this and, if it is indeed the case, does anybody have the part # for the bolts?!?

[yeehaw87]

I had a few bolts snap off when I had the diff cover off a couple years back. I would change the bolts just because I wouldnt want to be tightening them down n have them snap.

[asilverblazer]

I reused mine.

[Norseman]

I reused mine.

 

So have I. Twice. I also don't recall seeing anything to that in the service manual.

[pm26]

You should not have to replace these bolts. They are an equivalent of valve cover gasket bolts and I do not think anybody replaces those, except for rubber sealing washers on some vehicles.

 

These bolts should not be overtightened and they are not highly stressed bolts. I would recommend using a light coat of blue LokTite on the threads when reinstalling and torque them to factory spec or just tightened them snugly and as uniform as you can. Do not overtighten them, because you may distort the stamped sheet metal cover.

[C & A s Dad]

I am still trying to find out if the inspection plate can be removed from the rear diff on an '02 Yukon XL without removing the "track bar" that runs just behing the rear axle. Pick Ups do not have this track bar and there is nothing to interfere with the cover.

 

Can anyone answer this?

 

 

Sorry to jump your thread.

[90GMCZ71]

I am still trying to find out if the inspection plate can be removed from the rear diff on an '02 Yukon XL without removing the "track bar" that runs just behing the rear axle. Pick Ups do not have this track bar and there is nothing to interfere with the cover.

 

Can anyone answer this?

 

 

Sorry to jump your thread.

 

I have a 2000 Yukon (not an XL) and I have changed the rear diff fluid at least 3 times. No issues with the sway bar. I have also reused all of the bolts with no issues.

 

There is also a drain plug if you don't want to remove the cover (which I always do to clean the magnet).

 

//90GMCZ71

[Mr. Smith]

The bolts aren't torque to yield so reuse them. I have 3 times now with zero problems.

[Dave in Mpls]

Well, apparently GM wants to sell rear diff cover bolts!!! Here is the recommended GM procedure (pics probably won't come through). Go figure!!!

 

 

Lubricant Replacement - Rear Drive Axle (8.6 Inch Axle)

 

Removal Procedure

 

1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.

 

 

 

2. Remove the rear axle fill plug.

 

 

 

3. Remove the rear axle housing cover bolts (1). Discard the rear axle housing cover bolts.

4. Carefully remove the rear axle housing cover (2) and drain the lubricant into a suitable container.

5. Remove any gasket material from the rear axle housing and/or the rear axle housing cover.

6. Inspect the bottom of the rear axle housing for excessive metal particle accumulation. This accumulation is an indication of extreme wear.

 

Installation Procedure

 

 

 

1. Install a new gasket and the rear axle housing cover (2).

 

Notice: Refer to Fastener Notice

 

Important: Do not reuse the rear axle housing cover bolts.

 

2. Install the new rear axle housing cover bolts (1).

 

Tighten

Tighten the bolts to 40 N·m (30 lb ft).

 

3. Fill the rear axle. Use the proper fluid. Refer to Capacities - Approximate Fluid & Fluid and Lubricant Recommendations.

 

 

 

4. Install the rear axle fill plug.

 

Tighten

Tighten the rear axle fill plug to 33 N·m (24 lb ft).

 

5. Lower the vehicle.

[pm26]

What you posted is a typical factory shop manual procedure. I have seen something similar elsewhere. They always tell you to discard certain washers, especially lock washers, but nobody ever does. Especially at a dealership. Do you believe that any GM tech at a dealership will actually discard those rear differential cover bolts? They most likely do not even stock them in their parts department. In fact, I dare you to call your local dealer and find out if they have these bolts in stock.

 

As someone correctly stated, you normally only replace bolts that have been torqued past their elastic range into the plastic region, so they become permanently elongated. This is the case with some cylinder head bolts. If you look at a stress vs strain diagram, there is a straight line up to the plastic region. The straight line represents the elastic range, where the bolt elongates elastically, in direct proportion to the stress applied, but returns to its original length when the stress is released.

[KB06YUKONXL]

I asked this question of 2 mechanics at 2 different GMC dealerships because it does say to replace the bolts on the diff cover with new ones. Both guys looked at me like I was from Mars. They said they never replace them ever and never heard of that practice. I didn't want to ask them if they had ever read a service manual and decided to ask the parts guy. Again I got the outerspace look and he wondered why I would throw away perfectly good bolts. Then he checked and didn't have any in stock.

 

Their advice...clean them off with a small wire brush, apply 2-3 drops of blue loctite and re-torque. The gasket goes on dry.

 

Is there some disconnect here?

[pm26]

Personally, I would be looking to replace the cheap,crappy, flimsy stamped sheet metal OEM differential cover, rather than the bolts. Mine is already rusting and the truck has 5k miles on it and sits in the garage all the time.

 

And I bet the manual does not say "discard the cover and install a new one". It should.

[KB06YUKONXL]

Personally, I would be looking to replace the cheap,crappy, flimsy stamped sheet metal OEM differential cover, rather than the bolts. Mine is already rusting and the truck has 5k miles on it and sits in the garage all the time.

 

And I bet the manual does not say "discard the cover and install a new one". It should.

 

 

Look at the bright side...at least it's not covered with leaking gear lube.........

[KB06YUKONXL]

Oh yeah..almost forgot. FWIW I am going to by some stainless steel bolts or grade V bolts the equivalent size to replace these and be done with it. Sheesh....