Messed up rear differential cover change

[Schurkey]

The cover on the 10.5 axle under my '97 K2500 was so rusted that it had actual holes in it.

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I bought a new cover.
www.amazon.com/gp/product/B00M38FI9A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Two of the bolt holes in the cover were undersized, had to be opened-up with a die grinder and rotary file before the bolt would go through. I don't remember which two holes they were.

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GM has a bulletin on synthetic gear lube vs. RTV Silicone; supposedly the synthetic gear lube used by the axle manufacturer interacts with the RTV Silicone used by the axle manufacturer, the Silicone is degraded by the synthetic lube. I don't think this can be generalized to ALL synthetic gear lubes, and ALL RTV Silicone sealers, though.

I would, in general, prefer a paper gasket to RTV Silicone, but I've used both with success.

For the record, Permatex makes a "special" RTV Silicone specifically intended for use with gear lube.
www.amazon.com/Permatex-81182-Gear-Gasket-Maker/dp/B0023GM2KK

IF (big IF) the bolt hole really-is screwed-up, I'd cram a Heli-Coil (or equivalent) in there without hesitation.

 

[Pinger]

Not seeing the need for a Heli-Coil - just drill and tap to a larger size and enlarge the hole in the cover to suit.

 

[DDTurbo]

I recently did my 2001 K2500 Duramax and had no problems with the GM gasket, cover, or bolts.

 

[fancyTBI]

I recently did my 2001 K2500 Duramax and had no problems with the GM gasket, cover, or bolts.

That’s an entirely different platform.