[Fire70304]

2003 GMC 2500HD 4x4 Ext. cab short bed D/A 118000 miles, no lift, t-bars never cranked, 265/75/16 BFG All-terrains with less than 2,000 miles on them. stock as stock gets.

I took the truck in 300 miles ago for injectors to be replaced, warranty covered, get my truck back, all is well. A few days later I'm getting vibration from under the truck somewhere at speeds from 55 on up. Its not constant, sometimes only when on the throttle and stops when I let off, but sometimes also occurs when I let off the throttle to get off at an off-ramp.

I'm struggling with describing the vibration. I don't feel it in the steering wheel, I guess I hear the vibration more than I feel it, if that makes any sense. I crawled under the truck, CV boots are intact and not leaking, both bolts for the front track bar are in place and seem tight. Shocks aren't leaking fluid. Front driveshaft spins freely while in park, rear u-joints seem to be in good condition (chocked wheels, put in N, try to shake driveshaft and noticed no slack),Trans if full of fluid, transfer case if full of fluid (very dirty colored fluid, almost looks like old oil not dex III, but full).

It snowed when I got my truck back, and noticed that I had snow/ice frozen to the insides of my wheels, so I got all the ice off. It's been up around 32 lately, no snow on the wheels, and vibration continues. I looked to see if any of the wheel weights could have been knocked off from the snow, but all the weights appear to be in place.

Where do I go next? Thanks,

Tony

 

[Walldo]

Start with the easy stuff, have the tires checked for balance/out-of-round, bent rim, alignment, carrier bearing. hope this helps.

 

[DnHolland]

Look at the tread on your tires and run your hand over it. If you notice a funny wear pattern that could indicate an out of balance condition or a bent wheel. Try rotating the tires front to back and see if you feel the vibration in the steering wheel or if the noise changes at all.

 

[Fire70304]

I'll try rotating the tires first. It "feels" like it comes from the front, but almost like it's directly under the cab, like the front driveshaft area. I'll report back what I find. I feel it every day, so I should be able to pin it down somewhere. Thanks.

 

[Deere3500]

Sounds to me like the front driveshaft is out of balance or maybe the splines have wore...maybe try removing the front driveshaft, go out and engage the 4x4 and see if it does it still. I have had bad front d shaft vibes on an 81 chevy i had and my 2000 gets it slightly at certain speeds in 4 wheel! Hope this helps!

 

[Fire70304]

Sounds to me like the front driveshaft is out of balance or maybe the splines have wore...

Sorry, new to the IFS game, I've been a solid axle guy until this truck, but why would the front driveshaft spin in 2 wheel drive? I know there aren't locking hubs, but I assumed there was some type of actuator in the front diff to lock / unlock the front drivetrain??? I'll try pulling the d-shaft tonight.

And as a side note, i didn't get a chance to rotate the tires, but I did notice a slightly odd wear pattern on the front tires. All of the tread looks great until the very outer edges, maybe the last 3/4" of the outside. One treadblock will be slightly higher than the one behind it, then shorter, then taller..... almost feathered I guess, but no more than 1/16" differences.

Could be alignment, but it could be that vibration source causing the front end to hop around and wear like that too.... Troubleshooting continues.

Should that dark t-case fluid tell me anything? I will drain and refill this weekend to check for metal shavings, but shouldn't dexIII still look red even if it is dirty?

 

[Deere3500]

My appologies...I was under the assuming that you were having the problem in 4 wheel drive. If your having the vibration all the time, I would definitely rotate the tires before removing the front driveshaft. You are correct that the front driveshaft doesn't turn unless the 4x4 is engaged. That wear pattern on your front tires is one downfall of the ifs. I believe its considered cupping. But definitely start with rotating the tires. Easiest place to start eliminating. Again sorry about the misunderstanding. Good luck!

 

[09dave52]

After rotating the tires I would drop the rear drive shaft and check the U-joints next. They can be getting a little rough and you wouldn't feel it by just twisting the drive shaft and feeling for slack.

 

[Earl87gta]

With a 118k on the trruck I would bet its a wheel barring going out. jack the front up one side at a time and give the hole wheel a push and pull and see if it moves in and out I bet one of them does. It seams to be a trouble that a lott of us have had.

 

[Fire70304]

With a 118k on the trruck I would bet its a wheel barring going out. jack the front up one side at a time and give the hole wheel a push and pull and see if it moves in and out I bet one of them does. It seams to be a trouble that a lott of us have had.

Well, we have a winner. Passenger side tire has about 1-2" freeplay. Thanks for everyone's help! Time to find a deal on wheel bearing assembly....

 

[Deere3500]

Congrats!! Glad you found it!