Occasional rumblestrip type noise under truck

[Dave4x4]

Friend of mine has a 2001 dually ext.cab 4x4,8.1/alli. It makes a noise once in a while that lasts for only about 2 seconds while your driving that sounds just like running over a set of rumble strips. Somewhere underneath,from the cab area back,not in the front. Have not found a way to make it do it yet, just happens a few times every time you drive it. Any ideas out there????? thanks.

[4x4man]

OMFG!!!!
I thought my truck was the only one that did that!!
Mine does it to, no ill effects, just here this wahwahwah and then goes away, sounds like it comes from the front of the truck, right??

I have no clue what it is, but decided not to make a stink about it as no one else has posted about this until you....
But like anything else, knocks, clicks, ticks, etc are considered normal by GM, this was probably another of those free "features"....

Bob

[Idahobidcaller]

I had a Suburban that every once in a while would sound like driving over a rumble strip or cattle guard when taking off from a dead stop. Service writer after service writer would ride with me and could not ever make the noise happen. They all looked at me as if I were trying to steal their last born child. Then one day while describing the sound again to the service writer, a older mechanic happened to be walking by. He stopped and politely said that my truck has a limited slip rear end, and I need to change the diff fluid and put in the additive. He also said that I should change the rear end fluid at least once per year, depending on how rough I use the truck. Anyway, could the noise you have be as easy as having a rear end limited slip that needs an additive?

[Dave4x4]

4x4man:
It sounds to us like it's toward the rear but hey who knows,it dosen't last long enough to really know. It can happen anywhere and any speed from about 30mph on up to max. Pulls the trailers great if you don't mind the Alli whine,and the quart of oil every 1100 miles.

[mdrag]

Dave4X4,

Welcome to the forums, plenty of great info around here.

I don't recall hearing of a similar complaint in the past. If your friends truck has ghe G80 locker option, it is not considered limited slip and does NOT require an additive. The recommemded GM synthetic lube is $$$$ ~$16/qt + S/H from www.gmpartsdirect.com, and much debate has occured on whether other lubes meet the spec. If your friend has not yet changed the rear end lube, that would be a good place to start. GM recommends changing it after 500 miles of towing - a fairly easy job since there is a drain plug and the diff cover does not have to be removed.

Another idea would be to check if he has the one or two piece dirveshaft. There is a service bulletin pertaining to launch shudder on acceleration, with the fix replacing the two-piece driveshaft with a HUGE one piece unit. If his truck qualifies for the DS replacement - just MAKE SURE THE SERVICING DEALER DOES NOT CUT OUT THE CROSS MEMBER - only the bearing carrier plate needs to be removed - THE CROSSMEMBER SHOULD NOT BE REMOVED!!! There have been a number of posts on this being messed up, resulting in dealer buy backs.

Search the forums for rear end lube, drive shaft, etc. and you should find multiple topics to get additional information.

[4x4man]

Dave4x4

Mine seems to do it only around 40-50 mph if I am accelerating and then letting off the throttle. Unfortunaltely it is not recreatable, just happens, and like you said by the time it catches your attention it is gone.
I have the one piece driveshaft from the factory in my truck, and have changed the rear diff fluid at 2,000 miles once I finally got my towing time in...
The noise doesn't bother me, just has me curious, that's all.
Almost 8,000 miles on my truck and lovin' every minute of it!!

Bob

[ZFMax]

Mine makes a noise like that, almost a vibrating kind of a noise, generally as I'm slowing down and lightly on the brakes. Seems to happen more cold than hot, and certainly doesn't happen all the time or last very long when it does. It just started doing this recently and seems to be slowly getting worse.

ABS? I did just rotate my tires and they were getting pretty uneven, the rears have been wearing much faster than the fronts. Does the braking system detect different wheel speeds front and rear and do something?

Or a fuel pump?

Mine's also a 4x4, is that a common denominator in this issue?

[Barc]

Add me to the list of "rattlers"!! Mine does it very consistently at 800-900 rpm on acceleration ONLY. The slower you take off the longer it lasts - it is definetly coming from the rear of the truck!! My guess is an exhaust hanger or something exhaust related, in my case. I'll stop at the dealer tomorrow and round up someone to go on a ride along - I think I'll stick him in the box!! :D Will post results if I/we come to any conclusions!!! :confused: