Possible bad rear axle?????? Tranny?

I went off-roading on Wednesday, Only problem is...
I now have a loud humming noise that is coming from my driveline.
It increases with vehicle speed (not rpm), it only does it going foward, it stops when I put it in Neutral or I take my foot off the gas and coast, and it goes away quite a bit when I put it in 4-HI. Or I go faster than 55 mph
The noise is similar to that which big tires, or snow tires make. (neither of which I have).
I took it to a tranny shop today and we went out for a test drive. The mech seems to think that it is a bad pinion bearing....
Any thoughts?
If it is a bad pinion, is it a difficult job to do?
Any other ideas on what to do? I am on a rather tight budget so I really don't want any suggestions about swapping in Dana 60's or the like.
(although, I wouldn't mind a D44)

I checked around at the junkyards today and a D35 goes for about $175, and a Chrysler 8.25 goes for $250. Are these prices high?

This is my DD so it needs to get back on the road as soon as possible.

TIA
Seth

Have you checked the u- joints? If your sound comes from the rig under pressure ( not coasting or Reving ) I'd look there first and then go to the more expensive, headache causing problems...

two weeks ago I changed the u-joints on the front axle. I haven't changed the driveshaft u-joints because they appeared fine. I just drained the fluid, and I'm guessing it's not supposed to be milk-chocolate color?
Could that be the downfall?

Try moving the yoke at he pinion up and down, there should be like zero play (is your seal leaking?) often when the pinion bearings go bad, the seal starts to leak.
I´ve driven d35´s for years with odd hums and roars, everything from slightly rounded spider gears to very loose carrier bearings. Something that always seemed to help as a remedial cure (other than replaceing the worn parts) was a load of Moly B gear additive.

There is no noticeable play at the yoke. Nor is there any leaks that have developed. While I was changing the fluid, I inspected the gears. One the ring, one side of the gears showed very little wear (I'll assume this is the side that is engaged in reverse) the other side was vry shiny and the edges were sharp. Is that bad?
If the diff is indeed "bad", what are the chances of it blowing up if I don't repair or replace?

Well, my brother and i took the junk out for a drive tonight and we took turns sitting in the back, and the noise is definitely coming from the rear...

If I do need to get a new axle, I need to know the current gear ratio, correct? How do i find that out? The tags on the axle are so corroded that it is unidentifiable.

I always open up the rear end, count the ring gear teeth and the pinion teeth then divide.
Before you go to all of the trouble, doing the entire rear end, see if you can figure out exactly what the problem is.
My experience is, due to normal wear and tear, the carrier bearings often wear loose, around 130,000 miles. High speed driving can overheat the spider gear cluster and cause problems, the outside axle seals and bearings do fail.
Try taking a pry bar and moving the entire carrier up and down, left and right. Loose/worn carrier bearings will make it howl. And also change your contact patch on the ring and pinion, which will cause odd wear (the howl).
Look close at the ring gear and check for discolored patches, straw (yellow brown) or blue patches, an indication of heat and poor contact patch.
Noise in the drivetrain travels, it´s often hard to localize. Saw one mechanic, change the outside wheel bearings and come to find out later it was the rear tranny bearing, sure sounded like the wheel bearings.

Well, I got under the rig this morning and I had my brother put it in foward and reverse, while I payed close attention to the rear end (of the XJ). When it was put in gear, the driveshaft was able to make a 1/4 revolution. Is this normal? It also seemed to move up and down about .025. Is it supposed to do that?

A junkyard in town has an 8.25" out of a '95. Will Ihave any prblems swapping them over?

88woody said:

A junkyard in town has an 8.25" out of a '95. Will Ihave any prblems swapping them over?

Click to expand...

If you have a D35 in there now,the U bolts will be too narrow,8.25 will require 3" U-bolts.
Your drive shaft may be too long as the" snout" on the 8.25 is longer.
HTH
Wayne

yeah other than the new u bolts, everything bolted up underneath my 89 when i swapped thge 8.25 in for the d35. the driveshafts was longer but fit. its pretty much all the way in though. before i used to have about an inch of the top hanging out of the yoke or whatever on the rear of the tcase but after the axle swap im all the way in. im just gonna lift it a little to fix this haha