drivetrain noise??

[pete m]

This weekend I finally got to tow something with my`06 LBZ 2500HD. I was towing a `28 tag trailer that weighed 8000 lbs loaded. I noticed a slight vibration and "growl" from the transfer case back, possibly U-joint or driveshaft coupler, truck is a long bed crew cab and has a center carrier bearing, when driving from 56 to 64 MPH only, did not do anything lower than 56 and stopped at 64, went as fast as 70 with nothing at all, only in that speedrange. I went 525 miles on this trip, I have not heard anything when not towing. I did check the transfer case and it was full of fluid, I check it regularly since I had to replace one in my 2002 truck a few years back due to it running with no oil in it due to the infamous "transfer case leak". This one was full and I don't think its that. Any ideas??????????????

[Mark Rinker]

Were you running in 2HI or 4HI? I assume 2HI, but it sounds just like the vibration I am used to, when towing in 4HI, which is like all winter long.

Not to dismiss your concern, but there are vibrations and noises when towing that is just that - loaded towing sounds. My trucks have all seemed 'quiet' and 'light' when driven around empty, which is the exception and not the norm for me.

Throw a load behind them, and there are sounds of the suspension, drivetrain loading up and working. Pops come from the front a-arm bushings when the front end loads and unloads with 2K# of tongue weight on the pintle hitch - especially when in 4HI. You should hear what 18K# sounds like, from Minnesota to Florida. Sometimes you wonder if the next hill will be the last one!

My advice is to check everything like you have, grease everything that can be greased, throw loads behind her and LET 'ER BUCK. :)

[pete m]

Hi Mark, believe it or not being in Buffalo, and towing to middle Ohio, I was in 2-HI all trip, only time I was in 4WD, was when I attempted to break the trailer loose from where it had been sitting since Oct., I had to put it in 4 LO and it took quite a bit to get it out, i was worried for a while when i had all 4 tires spinning and was not moving, it finally got out and I switched to 2 hi.
The vibration and "growl" was weird because it was only for such a short span of speed, I figured if it was something major it would get worse as speed increased.
What do you think of the fuel mileage numbers I got? Was not flat towing, there were some hills, not like going thru KY or TN, but still had some hills, truck didn't downshift out if 6 at all I don't think. Its so much quieter than my last truck was because it had an aftermarket exhaust that was loud, this one is all stock. I got better mileage numbers towing this same trailer with my LLY dually, that weighed more, not sure why?.