4wd/front End Going Nuts!

[T4RBoarder]

So there is a story to this...bought the truck back in august. Soon after I bought it I started hearing a moaning/groaning sound when taking a sharp right turn at speed (the amount of moan depended on speed/how much the truck shifted to the left). Thought it might have been a bad wheel/hub bearing so I took it to two shops. One dealer and one family friends independent shop. Both couldn't find anything wrong and placed the diagnosis on the tires. Few weeks later had a flat and got brand new tires, sound still there. I just started to deal with it but then I cranked my TBs and the sound disappeared completely for a good month. Last night I went out to the truck and got in to leave and in the DIC had "service 4WD" displaying. Left the truck for the night and took another car, today I got in it and no message was displayed at all but now I have that old moan/groan(but louder) all the time esp around 40mph. It gets less noticeable at a highway speed and at really low speeds I can definitely feel it with my foot on the floor its like something is catching in there and rubbing or grinding.

 

Does anyone have any ideas? I have heard a lot about bad encoder motors but 4WD engaging/disengaging works perfect. 03 Tahoe Z71 w/96k.

[TedH]

So there is a story to this...bought the truck back in august. Soon after I bought it I started hearing a moaning/groaning sound when taking a sharp right turn at speed (the amount of moan depended on speed/how much the truck shifted to the left). Thought it might have been a bad wheel/hub bearing so I took it to two shops. One dealer and one family friends independent shop. Both couldn't find anything wrong and placed the diagnosis on the tires. Few weeks later had a flat and got brand new tires, sound still there. I just started to deal with it but then I cranked my TBs and the sound disappeared completely for a good month. Last night I went out to the truck and got in to leave and in the DIC had "service 4WD" displaying. Left the truck for the night and took another car, today I got in it and no message was displayed at all but now I have that old moan/groan(but louder) all the time esp around 40mph. It gets less noticeable at a highway speed and at really low speeds I can definitely feel it with my foot on the floor its like something is catching in there and rubbing or grinding.

 

Does anyone have any ideas? I have heard a lot about bad encoder motors but 4WD engaging/disengaging works perfect. 03 Tahoe Z71 w/96k.

 

Does it make the sound regardless of being in 2WD or 4WD? I found on my '03 Silverado Z71 that if I drove it in 4WD on dry pavement and rounded a corner at slower speed, the truck appeared to slow as if the front wheels wanted to turn more slowly than the rear... I attribute it to the traction control and transfer case control systems. But, if your front drive is groaning, I'd have somebody take a look at the 4WD actuator or the transfer case control module (TCCM). Also, have a shop tell you what the service/error code is behind the 'Service 4WD' message. There are multiple codes that can be behind that message and that may tell you more about where the issue is in your system.

 

FWIW, I've been having a 'Service 4WD' message for the last year... without the front end groan. I had the 4WD Actuator replaced, then my 4WD control switches started flashing off and on and the truck took too long to switch between modes (whether I was sitting in the driveway or driving at 45mph or slower), so I replaced the in-dash switch also. I still get the 'Service 4WD' and the code behind it is D0300. If I recall it correctly, I believe it indicates a need to reprogram the TCCM. My message comes on at initial startup once the automatic trans reaches 3rd gear. I reset the message and it doesn't appear again until the next time I start the truck and it reaches 3rd gear. My in-dash switch and 4WD Actuator replacement appear to have helped some also; less hesitation between mode changes.

 

I plan to take the truck to the local Chevy dealer soon for the TCCM reprogram. I am hopeful they will do what I ask and not try something totally unrelated (they tend to do that with most cars I take in).

[T4RBoarder]

yup, it makes the sound regardless of 2/4WD. It's not the same type of sound that you get when trying to turn on dry pavement in 4hi. At first was thinking it may have been partially stuck in 4wd (if thats possible?) but I can still cut the wheel all the way with no resistance of the 4WD.

 

I am totally stumped and need to drive it but I am just afraid that sound is doing something really bad.

 

Could it be a bad hub bearing?

[TedH]

yup, it makes the sound regardless of 2/4WD. It's not the same type of sound that you get when trying to turn on dry pavement in 4hi. At first was thinking it may have been partially stuck in 4wd (if thats possible?) but I can still cut the wheel all the way with no resistance of the 4WD.

 

I am totally stumped and need to drive it but I am just afraid that sound is doing something really bad.

 

Could it be a bad hub bearing?

 

I'm guessing that it has something to do with your 4WD. If the wheel spins normal when you are driving in a straight line, I'd think the hub bearing would be fine.

 

I've found that most repair shops can do a good job of diagnosing problems as long as they don't have to reprogram the TCCM. I'd find a shop you trust locally in Dayton and have them give it a good going over. Especially, get the diagnostic code behind the 'Service 4WD' message. That should establish a starting point whether it is the Encoder, TCCM, front axle, transfer case, etc.

 

Let us know what you find out!

[T4RBoarder]

well i decided to fiddle around a little bit and I tried to un-crank my TB and the sound has for the most part subsided. Any idea why? could it have been my CV joints at a bad angle?

[TedH]

well i decided to fiddle around a little bit and I tried to un-crank my TB and the sound has for the most part subsided. Any idea why? could it have been my CV joints at a bad angle?

 

 

OK. I'm stupid... what's a TB? Glad that solved it.

[DofD]

Torsion bar. Cranking the torsion keys will raise the truck's height a bit.

[J-man67]

I found on my '03 Silverado Z71 that if I drove it in 4WD on dry pavement and rounded a corner at slower speed, the truck appeared to slow as if the front wheels wanted to turn more slowly than the rear... I attribute it to the traction control and transfer case control systems.

 

That is caused by binding, which is bad for your vehicle. When you are turning, the inside wheels are rotating less then the outside and causes the binding when in 4wd.

 

well i decided to fiddle around a little bit and I tried to un-crank my TB and the sound has for the most part subsided. Any idea why? could it have been my CV joints at a bad angle?

 

It could have been if you cranked them A LOT, but you said the sound was there prior to cranking....correct?

[TedH]

I found on my '03 Silverado Z71 that if I drove it in 4WD on dry pavement and rounded a corner at slower speed, the truck appeared to slow as if the front wheels wanted to turn more slowly than the rear... I attribute it to the traction control and transfer case control systems.

 

That is caused by binding, which is bad for your vehicle. When you are turning, the inside wheels are rotating less then the outside and causes the binding when in 4wd.

 

well i decided to fiddle around a little bit and I tried to un-crank my TB and the sound has for the most part subsided. Any idea why? could it have been my CV joints at a bad angle?

 

It could have been if you cranked them A LOT, but you said the sound was there prior to cranking....correct?

 

 

What causes the binding? Not meaning to hijack this thread.

[2000DV4.8]

I found on my '03 Silverado Z71 that if I drove it in 4WD on dry pavement and rounded a corner at slower speed, the truck appeared to slow as if the front wheels wanted to turn more slowly than the rear... I attribute it to the traction control and transfer case control systems.

 

That is caused by binding, which is bad for your vehicle. When you are turning, the inside wheels are rotating less then the outside and causes the binding when in 4wd.

 

well i decided to fiddle around a little bit and I tried to un-crank my TB and the sound has for the most part subsided. Any idea why? could it have been my CV joints at a bad angle?

 

It could have been if you cranked them A LOT, but you said the sound was there prior to cranking....correct?

 

 

What causes the binding? Not meaning to hijack this thread.

 

 

When you turn, the inside and outside wheels need to turn faster than the inside wheels, and the front wheels need to turn faster than the rear. When in 4wd, the transfer case engages the front driveshaft, which can only turn at the same speed as the rear shaft, hence the binding when the front wheels try to turn faster than the rear.