I really noticed it tonight coming home from work since I generally don't have my radio on or anything during my 25min ride back, so I just listin to my truck and keep an ear on how he's doing. Tonight though, and I have been noticing it here and there for a few months, under heavy throttle around 3k rpm or so, right around that range it is most audible. It's a steady wus-wus-wus-wus-wus sounding noise coming from somewhere under the back of the cab or farther back. It matches my engine rpm as it increases and decreases, although anywhere under 2k and above 4k it isn't audible.

Anyone had this issue before or have a good idea what it might be? Aside from the noise everything feels just fine.

Have the 3.9 magnum and 42rh, ext cab. 2wd

 

My back tires make that noise when im moving at slower speeds than what your saying. But if it matches engine speed, i would lean more towards a u-joint, or your muffler might be going back. But first and foremost, check your diff fluid to make sure its full

 

It isn't tires or U-joint, my U-joints have been bad for more than a year and don't make that noise..they just clunk alot..lol and the tires are nearly brand new and i know what the sound for those are...my old man thinks it may be a bearing somewhere possibly, but we are putting a super-lube thing he got for the rear end in the fluid maybe..not sure if we will yet but just trying to see what all it could be before i dive into the $300+ cost of getting an lsd.

 

If you know the ujoints are bad then id replace them first. Just because they haven't made that noise in a year dont mean it cant start making that noise now. Then if it dont fix it you know the $30 you just spent isn't going to cost you $300+ in repairs and you dont have to do it when/if you install the LSD.

 

I actually have the U-Joints, just not sure how to go about putting them in since the ones I have experience with are GM type that screw in...these are pressed in I think and not sure if it is something I can do in my garage. Can you use a C-Clamp to press them in?

 

Take it to most automotive machine shops it will be $5 a U-joint to press in and out.