Bearing replacement, front diffs

[DFrank]

Finally took my truck in to a mechanic to diagnose a driveline noise.



He says it needs bearings in the front differential. Wants $1,100 for it.



Says it needs many new steering components; wants another $1,300 or so for that.



Anyone care to guess how quickly my bearings will disintegrate? I plan to keep driving it as is for a while yet.



I am fairly mechanically inclined, but the inside of a differential intimidates me. What would be involved in replacing the bearings myself? Are there special tools needed to get the steering done, other than an alignment bay?

 

[champspa]

pull the axles and get a spreader. the dif will come out after you spread the housing. that's a summary getting the axles out can be mean enough.

 

[RVTRKN]

How many miles are on your truck? You don't hear about diff bearing failures. I guess its time for Dyna Trak, they do have complete assembly's for sale.

 

[DFrank]

it's got 125K. I may have let the front fluid go unchanged for too long, after reading so many people bragging about how long their amsoil lasts in these things and seeing how super clean the rear looked when it was changed after somewhat extensive (40K) miles. I didn't write it down, but I bet I have over 60K on the front (amsoil) fluid now. I'll never know if that did it, but I wish I didn't have to wonder.

Anyone know what I should have to pay to have this done professionally? should I be looking for a new diff at a junk yard?

 

[rscurtis]

It depends which bearings are bad. If it is just the carrier bearings, that is a relatively easy job on the AAM. You don't need a spreader, that is required on the Dana axle. OTOH, if it needs pinion bearings, that is a little more difficult, as you'll have to be able to hold the pinion flange from turning while you apply 400+ ft/lbs of torque to collapse a new bearing spacer.



Going by the good track record these axle assemblies have, I would want to get a second opinion on this repair.



As Champsa indicated, you're going to have to pull the axles to do this. While you're at it, if you plan to keep the truck, now is the time to install a free-spin kit.

 

[amsoilman]

Is this guy telling you the "outer" bearings need replacing, or the carrier bearings?

 

[ENafziger]

Wow... I agree with the second opinion. Is your driveline noise at all speeds? Do you still have the noise with the front driveshaft out?

Is there a possibility that the axle tubes are bent? This is fairly common with these trucks if you hit a curb hard, or get a little spirited off road.

Before I'd put that kind of money into it, I'd look for a replacement front end. I've seen them complete for $700 on different boards.

--Eric

 

[jelag]

I have several of these trucks... . all now over 100K with one over 300K, we've never had problems with the front bearings... Hub bearings and U-Joints, YES but nothing in the differential..... these differentials are designed to go lots of miles... on my stuff we change the oil at 150K miles.....

Unless you've a seal go out and run this on low oil... . I personally don't think you have a differential bearing problem... .

 

[amsoilman]

The "hub" bearings are sealed bearings, and do not get lubrication from the gear oil. These are the outer bearings in the front axle. The carrier bearings are lubricated by the gear lube, but they are usually good for many more miles than what you have on your truck, in fact in the shop where I work, we have not seen a carrier bearing fail in several years.

 

[TCDiesel]

I have to believe its his Hub bearings/Assemblies,the AA front bearings Pinion & dif are more then stout, Now the rear axle bearing (Pinion) have been know too fail,I have Never replaced the front (Pinion-Dif) unless abused.

The front hubs bearings will start to buzz then hum then growl then grind,when they start to grind you have less then 100 miles before they lock up. .

 

[DFrank]

Thanks for all the advice. Enaf, when you say I could find a new front end for a reasonable price, what all would be included? Axle and steering components?

How can I truly determine what is actually wrong? I wish i had walked into the garage while they had it up and spinning to hear the differential (if thats what it is) myself.

If I were to remove the front drive shaft, it seems like that wouldn't even isolate anything except the u-joints on the shaft, as the diff would still spin with the tires.

The noise is speed variable, but doesn't seem to change with acceleration/decceleration or cornering.

Dave

 

[ENafziger]

If I were to remove the front drive shaft, it seems like that wouldn't even isolate anything except the u-joints on the shaft, as the diff would still spin with the tires.

That's true, but there have been plenty of cases with the front driveshaft on these trucks causing vibration/noise, so it might be worth a quick check.

Several of front ends I've seen have came complete with brakes, hubs, and steering linkages.

I'll PM you...

--Eric

 

[rbattelle]

I have several of these trucks... . all now over 100K with one over 300K, we've never had problems with the front bearings... Hub bearings and U-Joints, YES but nothing in the differential..... these differentials are designed to go lots of miles... on my stuff we change the oil at 150K miles.....



Unless you've a seal go out and run this on low oil... . I personally don't think you have a differential bearing problem... .

Listen to this man, he has many miles accumulated on several trucks and I think he's giving you good advice here. 40k is not long enough to kill the oil-bathed bearings inside a differential unless there is something else horribly wrong.



I agree with the others - the mechanic was probably referring to the hub bearings.



-Ryan

 

[DFrank]

I called back to clarify. He planned to replace the carrier and pinion bearings.

Am i being scammed? Its not happening anytime soon, unless it starts to get WAY worse.

 

[TCDiesel]

Hmmmmmm... I would exercise suspicion and proceed with caution!!!!!!

 

[rscurtis]

The only advice I could add at this point is that as the wheel bearing are removed, if their condition is suspect, replace them and road test the truck without going any further.



If it turns out they were not the problem, then only a little extra work was invested in taking the whole axle apart. Personally, I would not re-use bearings with that many miles on them due to the labor involved in replacing them.



There is also the possibility that if the noise really is from the R&P, perhaps only an adjustment of the preload or backlash is required, as opposed to an outright bearing replacement and all the extra labor involved with that.

 

[RVTRKN]

Get a second opinion and then if its still the carrier bearings, I would elect to get a complete front end from Dyna Trak with the latest designs. I was very impressed with the complete assembly, that I saw at a 4X4 convention. Why pay all that money out and get the same poor design with unit bearings.

 

[TBartlett1]

Have the mechanic put the truck on a lift, put it in 4wd and start it and run it.

Using a mechanics stethoscope you should be able to locate the noise source.

The pinion & carrier should generate very little noise.

If you are not sure what is normal listen to the rear axle.

Mite wana get a second opinion.

Differential bearing noise typically changes as you accelerate & decelerate.

Wheel bearing noise will typically change as you swerve left to right.

 

[S.Morris]

If the carrier and or pinion bearings are as noisy as being portrayed... ... then pull the front driveshaft.

Using a dial guage see if you can get any endplay on pinion. Also pull front cover and check backlash with same dial guage. If you find ANY end play on pinion, bearings are on way out. If ring/pinion backlash is more than about . 025 I would say carrier bearings are on way also.

Examine ring gear for improper wear marks caused by incorrect backlash.



All this assuming diff has never before been apart. These diff bearings are pretty tough... ... . only thing to take em out early is extremely low oil or Contamination... ... . READ water!



JMO



Steve

 

[DFrank]

Thanks Steve. I've pulled the driveshaft just now, and that alone seems like it makes it 10-15 % quieter. Not much, might be wishful thinking.

I assume I should replace the U joints on the shaft while i have it out, even if they seem fine. I guess I take it to a drive shaft place, or will someone like NAPA or Checker do that in house?

I also removed the front dif cover, but have no idea how to check for the stuff Steve mentioned, nor do i own a dial gauge that I am aware of.

I don't notice uneven wear, but I bet I wouldn't know it unless it involved blatantly missing chunks of gears.

Fluid looked clean to me. I'm going to replace it with some cheaper 80-90 gear oil i 've had kicking around and save the AMsoil for the rebuild, or new diff.

Any other suggestions?