Rear end whine 2001 s10 4x4

Elisa where ? are you working at, EXACTLY?
sounds like it's wheel /axle bearing, is it?
or the pinion bearing????? there are many bearings in any axle.

id bet $100 you didnt just pop in a new rear crankshaft bearing
as other poster guessed.

my guess is the rear axle seal leaked, GL5 lube
and soaked the brakes and all? or the front pinion?
the job requires, all Gear lube, be cleaning off all parts there.
after the job ends, or it will leak RESIDUAL GL5 (imagine a kitchen sponge?)
which axle , the 198RBI or the 226RBA??

this seal., must i guess?
so if this seal leaks, its because the bearing is bad, and beat the seal to deathh.
#1 cause.
when it leaks goes all over.
the rear has discs but has TopHAT, emrg. brake shoes
and those will be wrecked, (soaked in GL5 lube and leak after
and the shoes are wrecked too.) so did you clean all that and replace all that. (i can guess what you did or touched,)

The power steering pump is bad! God-Bless! or the rack and pinion leaks, check the pump first. the pump whines if low on fluid or bad.

Greetings, I read your question and I think Reliable-Store can help you in this. Here's the site link.
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clunking or grinding noises, wont accelerate to full potential,

this means the ring and pinion gear are worn, but when u do the gears u will need to also replace all the bearings as well.

The first thing I would do is check both differentials. Make sure they both are full of fluid. Make sure your transfer case is full. then I would check all the u-jionts and give them a good lube, the front one might take a needle point grease extension to get to the tight u-joints that you can't get the regular fitting on.

check the gear lube in resr end. if its low it will cause it to howl

check the belts and lake sure they are snuggly

IT COULD ALSO BE A BAD U JOINT IF THE REAR HAD NO LUBE IT WOULD BE JUNK BY NOW