Howling sound above 20mph in 01 k2500

[Centurion6R]

hi all, i've noticed recently a howling sound while driving above 20-25mph and it seems to calm down above 35, it's still there just more quiet. I'm bringing it into the garage on payday (friday) so i can check out/replace the diff fluids (it sounds like a pinion bearing might be a bit dry. Any other ideas what this sound might be? I didnt notice it till recently when the temps dropped to around -20 and below.

[Mark Rinker]

My '02 developed a pinion seal leak, unfortunately it wasn't discovered until the rear diff was 'dangerously low' on fluid, according to my independent tire/muffler/wrench shop - who happily replaced the seal and changed the fluid.

Shortly after, I started to notice a whine from the rear end, mostly noticable at low speeds - probably muffled by wind noise at higher speeds. I attributed it to the 'low fluid' event, and fully expected to be replacing rear gears, soon. Over time, everyone that used the truck got used to it, and we drove it that way for maybe 50K miles or so.

Prematurely, that (new) pinion seal started leaking - again! This time, it was up in the air at my local GM dealer, who recommended replacement the aftermarket seal pinion seal (...that was damaged on installation...) and the pinion bearing (?) - if I am remembering the name of the part correctly.

Whining noise then disappearred completely! This was all at well over 200K miles.


Feel free to print this out and hand it to your mechanic...maybe its the same scenario. ;)


(On edit...here is another very VERY similar thread, maybe a another candidate to print out...)

http://www.thedieselpageforums.com/tdpforum/showthread.php?t=35224&highlight=rear+end+whine

[Centurion6R]

thanks for the help again, mark, so i according to the post you added in there, i should be expecting almost 1500 bucks just to replace a pinion bearing!?!?! ouch!! haha well im going to put fresh fluid into the diff tomorrow when i get a minute, hopefully too much damage isn't done.

[Mark Rinker]

Pinion bearing, seal, new synthetic fluid was around $1000 when I had it done, as I recall...probably took them < 2hrs and $50 worth of parts...

[Centurion6R]

well it's not the pinion bearing i don't believe. I cracked open the filler on the diff, and the fluid is full and clean (not to mention there are no leaks at either end). So it's back to the drawing board on that one. Are the wheel bearings on these oil or grease lubricated? If so where is the grease fitting/oil add spot?

[Mark Rinker]

What leads you to that conclusion? Did the noise go away? The diff can be full and clean and still making noise if the pinion bearing is bad!

Axle bearings (at each end of axle tube) are lubed by same lube you inspected in the rear diff - no additional maintenance required.

[Centurion6R]

i suppose it still could be the pinion, there's just no leakage from the seal to make me think that was the culprit...im thinking i may just check the transfer case tomorrow as i did notice a very minor leak on the output shaft, is the fill plug the one to the rear thats about halfway up (right in front of the crossmember)? and also what kind of fluid to you recommend in the t-case

[crashz]

Yes thats the plug. I like the AutoTrac (for Auto T-Cases in 1/2 tons trucks and light 3/4 tons) fluid from GM, even if its on a manual T-Case. Or Mobil 1 ATF for the HD trucks

The cold might be giving you some problems. Have you "Alaska-fied" the truck and put synthetic fluids in? Maybe the PO had conventional oil in the diff? A standard 90W or 120W gear oil at -30 degrees will probably be solid. Which means the dry pinion bearing is not seeing any lube until the diff gets warm enough to re-liquify the oil.

[DmaxMaverick]

The rear diff should ONLY have full synthetic lube. 75-90 for normal use, or 75-140 for heavy duty or hot climate use. I wouldn't recommend 75-140 for cold climates (may cause noise and delay proper lubrication when extremely cold, like during AK winters). No non-synthetic is approved or recommended, regardless of use or climate.