4x4 operation

Jansen · January 19, 2005

My 4x4 system seems to be having issues (not experienced in my previous vehicles Jeep Comanche/F150). We had some snow today so I thought hey what a time to use the autotrac and pushed 4 auto. Every thing seems great except for a low pitch, cyclic hum that went way when in 2wd and got worse if you gave it more gas.

Secondly I figure I might as well try 4hi. 4hi was worse, when I turn the wheels it sounds like my tires are rubbing. I know this isn't the case because it doesn't do any of the above in 2wd. Anyone have any ideas? I'm to call the dealership tomorrow. Any help or ideas is greatly appreciated.

Jansen

biochemist · January 20, 2005

Hello, I also have a similare truck in my sig....same here also. Dealers say no problem, actually had them drive it (a few different dealers too...just for good measure). The rubbing is your tires rubbing... ....just do not turn hard on surfaces that have good traction...eats the tires and wears your system out....but the service guys say they are tough though, you know like the commercial ....they demostrated it to me by turing slightly on asphalt....does not sound good I admit. Def. get binding feeling and harder to turn.....is this what you are talking about? The noise is normal, just the front doing its job and the added noise of the transfer case engaged...sliglty louder in Auto...louder still in 4Hi....but I can only hear mine if everyting in the cab is off....so it is really not that loud, I can just notice if listening in a quiet cab...not heat, radio, talking...you know, like a hum/growl type of noise..dealer says once they are broken in a bit they will get somewhat quieter but you still ahve alot more parts moving in any of the 4wd modes... Let me know if I am being clear...

mjwencl · January 20, 2005

I just had my 2004 Chevy Silverado 2500 Crew's front differential replaced for a noisy whirring sound that got louder as you came to a stop in 4HI. It's quieter now but all the new trucks on the lot make a similar sound in 4HI / Auto 4WD. Don't know why.

My 2003 Chevy Trailblazer with a G80 4.11 rear and 4WD Autotrac makes no noise at all.

I don't know why some are noisy and some not.

Jansen · January 21, 2005

Thanks for replying. I have the sound that mimics brakes on metal. To hear this I have to have the radio turned down and noise at a minimum. I have an appointment at the dealership tomorrow I'll let you know how it goes.

Jansen

Jansen · January 21, 2005

The noise (brakes on metal) comes and goes as i turn the wheel left or right (not all the way though). Other than that at about 30 mph i get the cyclic hum in 4hi and 4 auto.

Jansen

mjwencl · January 21, 2005

Let me know what you find out from your dealer. And good luck!

USA1Fan · January 21, 2005

My 2003 Chevy Trailblazer with a G80 4.11 rear and 4WD Autotrac makes no noise at all.

I don't know why some are noisy and some not.

<{POST_SNAPBACK}>

Strange that you mention that. My '03 Trailblazer 4WD Autotrac w/G80 and 3.73 rear was silent in all modes too. And my '04 Silverado Z71 does make some noise in 4WD. (I took it to be normal, since every other full-size 4WD I've been in seemed to make some noise when in 4x4 mode too.)

biochemist · January 21, 2005

I think it will be deemed normal....all the service managers I drove mine with said that is the way they are....brakes on metal is exactly what they sound like...but not real loud. I drove a manual shift 4x4 (new) and it too made noise...so, as usual, it is normal. But, let us know what your dealer says........

Jim Brimhall · January 21, 2005

The noise you describe is typical. Gearing, etc. The feel you get in 4HI as opposed to 4Auto is due to the front dif being fully engaged. Commonly referred to as wheel hop or skip. Again, typical. The Auto trac only engages the front dif if the rear dif sences slip. I'm not sure about the Commanche, but my CJ5 and Grand Cherokee did the same. The following link is very helpful with Chevy Truck info.

http://chevytruckworld.tenmagazines.com

Join your local chapter and enjoy.

jb

Jansen · January 23, 2005

I hit the dealership on friday and took the tech for a drive. My truck did make the noise I described and the tech said he understood what my concern was but that since the redesign in 99' they tend to make more noise than before. He wasn't sure why that is but the T-case and front seemed fine to him and becuase nothing was coming through the wheel and no idicator lights were on I think its ok as well.

One thing he did say was that the lights on the switches have been problematic and that if one of the lights goes out it can trip the service light for the 4wd. Oh well, not going to worry about that one.

By the way, 2100 trouble free miles and switched to Mobil 1 today. Really liking the GMC

pablontx · February 6, 2005

I just had my 2004 Chevy Silverado 2500 Crew's front differential replaced for a noisy whirring sound that got louder as you came to a stop in 4HI. It's quieter now but all the new trucks on the lot make a similar sound in 4HI / Auto 4WD. Don't know why.

My 2003 Chevy Trailblazer with a G80 4.11 rear and 4WD Autotrac makes no noise at all.

I don't know why some are noisy and some not.

<{POST_SNAPBACK}>

As one of the posters above, I had to get my rear diff replaced....one of the bolts broke off and things got chopped up. Made a similiar sound as you described.