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2004 Silverado 2500HD 6.0L 4WD - Vibration at Highway Speeds...

RayMich

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Good morning guys! I am having a problem that I hope the truck gurus here can help me solve.

I recently purchased a 2004 Silverado 2500HD 6.0L 4WD extended cab truck with 99,000 miles on the odometer, to replace our older 2002 plow truck that is finally worn out.

Sadly, I didn't notice a sever vibration between 52 to 72 mph, because of heavy rush-hour traffic when I test drove the truck at the time of purchase.

NOW THE PROBLEM: The truck has a very nasty vibration between 52 to 72 mph. It feels like you are driving over nasty rumble strips. The vibration is not there below 52 and gradually goes away above 72 mph in 2WD mode. I had my local tire shop dynamically balance all 4 wheels, but the vibration is still there just as bad. Additionally, my son noticed an oil leak coming from the area of the transfer case.

I took the truck to my repair shop the next day and they found a cracked T-Case Adapter, which I told them to replace. Picked up the truck the next day and while on the highway on the way home I noticed the bad vibration is still there at 52 to 72 mph. By this time, the repair shop was closed so I went home.

The next day, my son again noticed a T-Case leak.

I then took the truck back to the repair shop and they found the leak coming from the seal between the T- Case and the T-Case Adapter, which they fixed under their warranty. They also found the front drive shaft U-Joint at the T-Case was binding up, so I had them replace that as well. Picked up the truck the following evening and again noticed the bad vibration at highway speeds on the way home.

( QUESTION: Does the front driveshaft still turns when the truck is in 2WD mode? - I was under the impression that the front driveshaft is disconnected when the T-Case is in 2WD mode, as well as the actuator on the front axle disengages the differential. - This is the electric shift 2-speed t-case.)

Today I spoke with the repair shop owner and he said to drop off the truck when I get a chance (hopefully tonight) and he will remove the rear driveshaft and send it to a balance shop to be checked ( Should have an answer for me in a couple of days ). I asked him about the U-Joints on the rear driveshaft and he said they looked fine, but they did notice one of the clips on one of the u-joint was loose so they "re-installed it." He also said that he had not noticed any damage on either driveshaft and no missing balancing plugs.

It appears to me that this nasty vibration is what caused the T-Case adapter to break as well as the subsequent gasket leak after the adapter was replaced.

Any suggestions and comments are greatly appreciated.

Thanks.
 

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FRANKENBURBAN
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The front shaft should barely turn at hwy speeds if everything is working. Check to make sure the transfer case is full of fluid and that "pump rub" hasn't gotten it. Does this truck have a 1 or 2 piece rear shaft?
 

RI Chevy Silveradoman

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I think the front driveshaft spins while driving. Only kicks in when the t case button is pressed. Then it sends the power to the front axle. That was the way I understood how the system works.
But I agree, check the t case fluid.
Sorry Ray.
 

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I think the front driveshaft spins while driving. Only kicks in when the t case button is pressed. Then it sends the power to the front axle. That was the way I understood how the system works.
But I agree, check the t case fluid.
Sorry Ray.
Negative, unless you have a full time AWD system, the front driveshaft should disengage via the CAD(black electric motor that screws into the right side tube of the front axle), and in the transfer case. They still spin some, but not much if everything is functioning properly.
 

RayMich

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Negative, unless you have a full time AWD system, the front driveshaft should disengage via the CAD(black electric motor that screws into the right side tube of the front axle), and in the transfer case. They still spin some, but not much if everything is functioning properly.
This is my understanding as well.
_________________________________________________

Thanks for all the responses.

This truck is a 2004 4WD Silverado 2500HD with the 6.0 L V8 and the 2-speed electric-shift transfer case. It now has a little over 100K miles.

My mechanic sent the complete rear driveshaft assembly, including U-Joints and front Yoke, to the balance shop last Wednesday but still haven't heard back. I asked them to inspect the T-Case internals and give me a quote for rebuilding it, but that hasn't happened yet.

Everything in my mind points to drivetrain being severely out of balanced that is damaging the transfer case. First noticed severe vibration from 52 to 72 mph (like going over rumble strips). Had all four tires and wheels dynamically balanced, but vibration still there. Noticed a transfer case leak that originated from a cracked T-Case adapter (crack looked like a thin fatigue crack on top-side of adapter). Replaced the adapter and refilled T-Case, but vibration persisted. A couple of days later, noticed another T-Case leak. They replaced the T-Case seals and the front driveshaft U-Joint at the T-Case that was binding up. They said both rear U-Joints look new and appear to be fine. Two days later, T-Case leaking AGAIN. Took truck back in. They have now sent complete rear driveshaft assembly to balance shop. I am having both rear U-Joints replaced and the T-Case inspected internally. Will have them rebuilt the T-Case if necessary.
 

RayMich

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GOOD NEWS ! ! !

Finally got the driveshaft back from the balance shop this morning. Replaced both output shaft T-Case seals, installed 2 new U-Joints and re-installed the drive shaft assembly.

I am happy to report that the truck now runs smooth as silk. I have not been able to talk to the balance shop tech to ask him about what made the shaft so far out of balance, but I will when things slow down a bit.

My mechanic is swamped with work right now, so we agreed for me to bring the truck back in a couple of weeks for him to tear down and rebuild the T-Case. I don't want to risk a blown T-Case while plowing this winter.


I want to thank everyone here for your comments and encouragement. I really appreciate it.

Best regards.
 
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