Well, this will be the third time dealing with my front Differential in my truck...

The first time, the dealer "Repaired it" - lasted around 12-15K miles, just out of warranty..
Second Time I just replaced it myself with a used boneyard 04 Yukon unit that ran perfectly fine, for about 8 months, and now..i'm getting the same crappy input shaft bearing noise I had on my other front differential.

Do the rest of you 1/2 ton guys have to replace these front units as much as your spark plugs?
If your at a light in 4wd and you nail it, does it make all sorts of wierd grinding noises and shudder the whole truck?
In 2wd at high speed - does your front end light up and act like its grinding itself to bits?

I believe the front shaft should always be spinning while the truck is in motion..but..I thought I should double check.
The Dealer replaced the 4wd switch the first time I told them the truck front end was locking up on me. The second time they "Rebuilt it"
The only thing that hasn't been replaced is the 4wd control unit and the transfer case.

I was going to finish the needed repairs on this truck, but if this is a common problem, Im going to save my cash and go with something else.

Any thoughts on what could be wrong?

 

How often do you "Launch" from a set of lights in 4WD.

They're not really made to take that kind of abuse man. They're a good diff...but if your trying to race with them you kinda need a center Diff (AWD T-Case) not a 4WD one

 

Only when necessary and not very often as I know it's hard on them.

 

I've launched 100+ times and with substantial power (in my humble opinion ) the only issues I have are wheel speed sensors and that damn autotrack switch. No grinding or sounds of any kind.

 

Year and model would help. The GMT 800 front shaft turns all the time. Previous years did not. The noise you are hearing might be a broken snap ring in the tailshaft of the transfercase. It is a horrible noise.

 

Sorry - 1999 GMC Sierra Standard Cab Short box
NVG-246 "Auto" T-Case
GT4 Front Differential (3.73 gears)

Its more of a squalk only under heavy load... but this is an old problem. Every once in a while, even under 2wd, the truck will bind up like the t-case is engaged. Hasn't happened much since the new differential was installed though.

I still have my old front diff. Everybody around here wants 1200 to rebuild it, which seems crazy... but mabee not? Im just wondering if there are Heavier duty load capable bearings and Races where they don't take a poop under any load other than baby steps.

 

I know that the front diffs are a fairly common failure, but I've never heard of anyone smoking more than one...mine is shot also, it growls while driving and I got a buttload of metal on the drain plug last time that I changed the fluid.

 

Yup - thats when I pulled my old one out and put the new/Used denali unit in.

It's the input shaft bearings, front and rear from what I could tell.

If you lift the rear of the truck up and leave the front wheels on the ground, shift it into drive (Block the front wheels obviously) you'll hear the growl too.
if you drop the front shaft out, and repeat the process, it should dissapear.
That's what I did to rule mine out.

I have to be fair - the used denali unit had 99K miles on it but it didn't have anywhere near the shavings that mine did. Plus...it was whisper quiet when I bolted it in.
Mabee its speed related?
I generally drive anywhere from 75-90 on I75. I limit everything over 85 just because the truck gets a funky vibration like a bad u-joint coming from the front end.

 

I verified mine by jacking the truck up on all fours and running it in 4wd and listening to the front diff with a stethoscope, there was no mistaking that the noise was coming from the front diff...that same day on the ride home from my in-law's the trans blew

 

i just rebuilt my front diff for 160 bucks.

it was simple.

get the necessary 8.25" ring gear rebuild kit and do it up.