Groaning and vibration from the front diff or axles only in 4wd

[RumorsOFsurF]

I tried searching the forums using several terms, but couldn't find any help, so I guess I'll start a new thread.


While I was at work last night it snowed a couple inches, so I engaged 4 high in my 2003 Yukon(NP246 T Case) when I was driving home. As I was driving, I noticed a noise and vibration that only occured while on the throttle, either accelerating or at a steady speed. Not while coasting. In Auto 4WD, the noise only occurs when the back tires begin to slip and the front kicks in. When I shifted back to 2 high the noise went away completely. I drove around the block when I got home several times, listening to the noise, and it gets much louder when turning. At low speeds (around 5-10mph) it's a groaning sound, and quite noticeable.
Before anyone says it's because I'm in 4 high on pavement, the ground was completely covered in fresh snow, and the traction conditions were low. It is difficult to even move in two wheel drive, and the G80 kicks in at inopportune times when you do and sends you all over the road.


I checked the front driveline and there's no slack as far as I can tell. The front axle CV joints will move a hair when I tried to jiggle them or whatever, but the movement was less than a millimeter...almost imperceptible.


As an aside, in the past I've noticed a VERY slight vibration when turning in 2WD in dry parking lots and such, but no noise really. Most people probably wouldn't even notice it.



So could it be the differential itself? Or could the CV joints be the culprit? It seems like it's the driver side to me, but of course that's where I'm sitting.

 

[Frankhenrylee]

Had the same thing happen a few weeks ago. Tried it the next day on an icy patch and didn't hear anything. Occasionally while in 2wd and the wheel is turned all the way it seems like it is binding up, a little bit like its in 4wd. Very interested to hear the outcome of this. Mines got about 110,000 but doesn't look like the torsion bars have ever been raised. I do have the lean on the drivers side, it almost looks like it has been lowered an inch on the drivers side, cv's are actually a hair lower than level. Doesn't seem like that would cause any damage considering alot of guys max theirs out.

 

[zaathur]

I would try a new cv shaft i have replaced a few 99-06 silverado cv shafts because of
front drive train vibrations and fixed the problem

 

[RumorsOFsurF]

Found out another interesting fact...My Dad's nearly identical '03 Yukon makes the same noise while turning in 4Hi, but no vibration while traveling in a straight line. Weirdness.

I compared them side by side today. I called the dealer and I'm going to take it in to have it looked at on Tuesday. Once again I'm glad I bought the extended warranty. Already had the transfer case replaced, so now the warranty has paid for itself and I'll be in the black if there's something wrong with the diff.

Not sure that's such a good thing that I'm having to repair or replace major drivetrain components all the time.

 

[zaathur]

let us know what it is, how many miles does your have

 

[DaRosa218]

How's the level of fluid in the diff? Mine was doing that in the rear due to low and old fluid. Switched it out to Lucas using the preferred weight of oil and put in limited slip additive. Never heard a noise again.

 

[Frankhenrylee]

Changed my diff fluid today. Front diff is probably F'ed. Drain plug had a chunk of metal along with alot of metal shavings. My brother, who is a parts manager at a local dealership, told me that they don't rebuild these, they just replace with a used part.

ADVICE: If you're looking at a used 4x4 go ahead and pull all of the drain plugs and check em out. I could have/should have passed on this one.

 

[rich5368]

Depending on mileage and how often it was changed by the previous owner, some metal shavings on the plug is normal. They arean't hard to rebuild though.

 

[andrew383]

Its a normal noise of the autotrac case..

 

[04SS99Denali]

slight vibrations/noise is normal when on pavement when in 4hi. when in 4hi your front diff is under load which is why the noise will only come out when in 4. change your fluid if you see alot of metal shavings then start looking for a rebuilt unit. noise from the front is usually not a good thing

edit: just read your post lol. look for a rebuilt unit from jasper or pull one from a wrecked truck at a junk yard

 

[Jay]

Front carrier bearings are glass in the 8.25" IFS differential and usually go bad when the spanner lock tabs break off, allowing the preload to come undone. Carrier bearing replacement is necessary in that case. You can usually get away with replacing just the carrier bearings by themselves. Unless, that is, you drive it for many miles in that condition, which will ruin the gears and pinion bearing too requiring a complete rebuild.

As long as all four tires are the same dimension, you shouldn't hear anything while in a straight line in 4wd. Might feel a VERY slight vibration with all the front parts rotating, but there shouldn't be a noise. Just don't turn on pavement while in 4wd (not a problem in Auto4wd since the front shaft likely isn't engaged at the tcase).

If you hear noise in 2wd then it might be a CV shaft. They are always turning on these trucks... the part-time 4wds just have an engagement motor near the diff to lock in the passenger side axle to the spider gear shaft in the differential. Meaning, while in 2wd only the CV shafts turn. While in auto4wd, the CV shafts, differential, and front driveshaft is turning with the tires, but not engaged at the tcase unless slippage occurs and the computer commands engagement. In 4wd everything is engaged and being driven by the tcase.

 

[Gordy]

Front carrier bearings are glass in the 8.25" IFS differential and usually go bad when the spanner lock tabs break off, allowing the preload to come undone. Carrier bearing replacement is necessary in that case. You can usually get away with replacing just the carrier bearings by themselves. Unless, that is, you drive it for many miles in that condition, which will ruin the gears and pinion bearing too requiring a complete rebuild.

As long as all four tires are the same dimension, you shouldn't hear anything while in a straight line in 4wd. Might feel a VERY slight vibration with all the front parts rotating, but there shouldn't be a noise. Just don't turn on pavement while in 4wd (not a problem in Auto4wd since the front shaft likely isn't engaged at the tcase).

If you hear noise in 2wd then it might be a CV shaft. They are always turning on these trucks... the part-time 4wds just have an engagement motor near the diff to lock in the passenger side axle to the spider gear shaft in the differential. Meaning, while in 2wd only the CV shafts turn. While in auto4wd, the CV shafts, differential, and front driveshaft is turning with the tires, but not engaged at the tcase unless slippage occurs and the computer commands engagement. In 4wd everything is engaged and being driven by the tcase.

Jay with that being said If you ar in 4 Hi, and hear some minor noise like an agressive tire sound, and do not hear that same noise in Auto 4wd would you still say that its a carrier bearing. I do have one rear tire that is wore more than the other three which are new (road hazar warranty replacements) but they are all the same tire. The noise is coming from the front though.

A bad front passenger hub was bad which I replaced, and quieted things down, but it is a little louder in 4 hi, but the sound in auto is the same as 2wd quiet, and no change.

 

[Jay]

Without hearing it myself in person, a few things come to mind.

Considering the difference between 4Hi and Auto4wd is only connection at the tcase (whole front end is turning in either case), at first it sounds like something in the transfer case as it would be powering the shaft in 4Hi.

Other than that, it could be a pinion bearing. There are two of these... a compression bearing near the pinion gear and the tension bearing near the yoke (both are tapered needle bearings). You put a preload on these during install, and the aggravating crush sleeve is what maintains this preload like a spring. The tooth design on the gears are a hypoid spiral design, which like all spirals creates a thrust force away from the point of tooth contact... in this case into the direction of the pinion while being driven.

While in Auto4wd, no slippage, the pinion teeth are riding the coast side of the ring gear teeth. Meaning little loading on the tension bearing of the pinion set. While being driven, the compression bearing takes the load of thrust.

Edit: when i say something in the transfer case i don't necessarily mean something is wrong... it could just be general binding. Even with the same "specified size" tires, if even one is off it can cause vibration. The speed of the pinion is the average of the two speeds of the tires it's driving. If one tire on the front, for whatever reason, is slightly off it can cause the spider gears to rotate even when driving in a straight line.

You shouldn't be using 4wd on dry pavement anyway.

 

[Gordy]

You shouldn't be using 4wd on dry pavement anyway. [/QUOTE]



Jay where have you been I learned more tonight than 24 hours of surfing the web. Good stuff Jay thanks for your contribution!


Oh, and I don't make it a habit on dry pavement. Just a couple of 1 block straight line test checks now, and then. I should say there is no noise on the snow.


Gordy