[Frank237]

Going to change the rear differential lube as soon as I figure out WHAT to stick in there.

I know the "WHAT oil should I use?" posts turn into a goat rope in short order. Not only here , but on the gun forums too. Lots of opinions.

The GM #88862624 has the ADDITIVE already mixed in.

Is there definitive proof that Royal Purple or the Amsoil lube is truly BETTER?

[Mr. Meh]

I'm going to run the ACDelco stuff until I have reason otherwise. Too many complaints about the other stuff out there with regard to groaning starting up after a bit. Already had to deal with incessant groaning with the 2016 SS before that was all sorted out. I don't want that with the ZL1.

[Deakins]

Probably no proof to be honest. The RP that came out of mine after 6 long track days still looked great for what it's worth. Probably had 18-20 wide open hours on it with minimal cool down periods and 8500 street miles.

[Wolvie70]

My rear diff had the groan and I changed mine with the GM with additive and groan is gone so far, been around 1200 miles.

[somewhatdamaged]

I'd stick to the GM w/ additive stuff......no groan for my diff. You may risk groan with other brands.

[Frank237]

Thanks Gentleman....got the GM stuff....Going to change it tomorrow.

[Frank237]

Changed out the rear diff fluid and was somewhat surprised how little ANYTHING I had in the oil...short of some black dust on the weak , drain plug magnet. It was sort of grey but no metal of any kind.

Installed the Gold Plug, magnetic plug when I refilled.

[Chutzpah]

Originally Posted by Frank237

Changed out the rear diff fluid and was somewhat surprised how little ANYTHING I had in the oil...short of some black dust on the weak , drain plug magnet. It was sort of grey but no metal of any kind.

Same here, looked pretty clean.. changed mine yesterday. It appeared that mine had just 1 quart or less in there though. As well, what was stuck to the plugs felt like the consistency of yellow pipe sealer ( mushy / sticky).

I didn't hear the or feel the groan this morning, so here's hoping the issue is gone @ 3300 miles.

[Frank237]

Originally Posted by Chutzpah

Same here, looked pretty clean.. changed mine yesterday. It appeared that mine had just 1 quart or less in there though. As well, what was stuck to the plugs felt like the consistency of yellow pipe sealer ( mushy / sticky).

I didn't hear the or feel the groan this morning, so here's hoping the issue is gone @ 3300 miles.

I found a bit more than a qt drained out. Refilled with basically the same amount.

My refill was to get the better, magnetic plug installed and to simply look at the oil in there. I had NO issues with groaning or noise.

I hope Your groaning issue is gone. It's a nice feeling when a guy can actually FIX something. Good Luck.