fcoreyxoxo

I have a 2000 Limited with about 230k miles on it. When I got it it had a whining noise when driving and louder when accelerating.
The front end is replaced with almost all new parts besides the axles/diff one side is a CV axle and the other is a regular one. My trans is a NP242 SelecTrac. I have not checked out the rear axles to see if those are both CV or not, but I am at a loss I'm hoping the noise is not the pinon bearing! The noise sounds more in the front. Any idea of where to start? I've already looked through the threads a little bit but some of them weren't too helpful.
Thanks!

RocketMouse

Is the nose steady? Or does it increase in frequency the higher the speed?

BwanaBob

Sounds like you recently got the Jeep and had some work done to it.

Whining can be a rear side axle bearing. At highway speed when you hear the whine,
veer left to load the axle bearing and see if the noise changes. Then try veering right.

An inner pinion bearing will whine or growl when accelerating and quiet somewhat
when coasting. An outer pinion bearing will be noisy when coasting, quiet when
accelerating.

The Jeep uses a solid rear axle, no CV joints. Just the differential and the side axle
bearings to worry about.

Make sure the rear differential is full of oil (80w-90 gear oil usually). If it is not full,
oil will not get to the outer axle bearings.

Whine can also come from the transfer case. Check to make sure the oil level
is up to the fill hole. (uses Dexron II)

fcoreyxoxo

It gets louder as I go faster, and there is a vibration right under the center console

fcoreyxoxo

Yes it had the noise when I first got it so I replaced the wheel bearings and did everything up front while I did the bearings just thinking/hoping it was one of the wheel bearings making the noise but it is constant plus a vibration when at high speeds but no death wobble so far.
if it is the inner pinion bearing should you just replace them all at once for them to all be new or does it really matter?
Also will check the fluids thats one big step I did not do yet.

BwanaBob

You'll save money over time if you check and find the real source of the problem
before buying parts. Do you do your own work or have a shop do it?

Good idea to change all the fluids when you buy a used car (engine oil and filter,
radiator (50/50 mix water/antifreeze), transmission, transfer case, both differentials)
so you have a point of reference for maintenance.

Is the rear pinion yoke loose? Any play in/out, left/right? Any leaks from the pinion seal?
Those are signs of a failing pinion bearing besides the noise. A little rotational play
is OK, that is just the spider gears in the differential moving normally.

If you find you have a bad pinion bearing, then it would probably be cheaper to swap
in a used axle assembly than to pay a shop to do it.

Check the rear brake area and wheel rims for any signs of an oil leak from the outer
axle seal. Also is a clue to a worn bearing. Leaks from a pinion seal or axle seal mean
you should open the differential, empty the oil and look a for bits of metal in the oil.
If there are bits, or the oil level was low or if there was a leak in an axle seal, then
you should remove the axle shafts and see if they are worn where the outer bearings
ride on them. The shafts have to be removed anyway to change a leaky axle seal.

Ask again on the thread if you have questions along the way.