so its mainly predominant at highway speeds but i can feel it in my seat and hear it coming from the rear of the truck. its a very low rumble and it droans. it goes hummm hummm hummm. I did notice my fill plug on my rear dif has some signs of leakage. i have not checked the fluid level yet but could that just be a result of low fluid? my u joints are solid. no play in them. clutch has less than 1000 miles on it and the same with the top end rebuild. my front end is also brand new alignment is perfect. The tires are old and are starting to crack so i have not ruled out the tires. My fear is that my third is going, any thoughts? Thanks in advance YTer's!

 

Rear axle bearings?

 

thats another thing i could look at. thanks, hopefully its just the tires/low diff fluid.

 

x2 on the axle bearing. Do you notice it more when your on the gas or off the gas or does it matter?

 

its more pronounced when on the gas but still there when off the gas. the faster i go the louder it gets, can start to hear it at about 75-80 km/hr so about 45mph.

 

Mine started humming at 60+ same thing your talking about and yes both bearings were shot Good luck

 

Sounds like axle bearings. I've had pinion bearings go bad that sounded fine while I was on the gas, but when I let off it was HORRIBLE.