Rear end lube and noise

[KShortell]

Hey all,

It's been a while since I posted something on the forum.

Anyway, I've had a mild nagging moan from the 10-bolt 3.73 rear end in my '86 Sub for a few years, usually only in the "float" or lightest of light acceleration. It's a wee bit louder these days at 145,000+ miles and I got to thinking a bit. This is where y'all come in.

GM specs 80W-90 for the rear diff. I was wondering if running 80W-140 would quiet things down a little. Since I only get 12-13 m.p.g. now, I don't see it hurting fuel economy too much. Anyone ever run a blend? As a kid, I heard about guys running the limited-slip additive to quiet even open diffs like mine.

I do tow a 3,500 pound boat/trailer combo on occasion; I've actually put 7,000 miles on the boat trailer over the years.

I've always just run the factory-spec lubes, but got to wondering. Any advice is appreciated. Thanks!

-Kevin
1986 Chevy Suburban C10 Silverado
350 SBC / TH700R4 / 3.73 / P235/75R15XL