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

[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