Here is the deal, I have a 93 T-100 4wd. It seems to have a noise in the rearend area now. The truck has 124,000 miles on it. When I drive down the road I can hear a noise that comes and goes, the noise sounds like a tire hum, but since the noise comes and goes I don't think that it is. In about every gear when I hit a certain rpm, I hear a hum noise and it last for a few mph (about 3 or 4mph) than it goes away, than I shift into the next gear and when i get a rpm it will hum again than go away, and it does this through all of the gears, first through fifth. If it was a tire wouldn't it make the noise constant ? Also the driveshaft doesn't seem to have any movement to it and the rearend is full. When i got it It was about 1/2 a qt or so low but, that was about 9 months ago and i topped it off than and the noise just started a week or so ago. Any ideas ?

 

if it is a manual trans check fluid level.

 

Fluid is good.

 

I had a pinion bearing go bad back there. It had become a constant humming/drone sound. By the time I took it in, it had spread metal bits all throughout the rear axle and other bearings. Had to have it rebuilt for $1200 or so. You might want to have it looked at before it gets too bad. Maybe if you drained the fluid and looked for metal you could see if that is the problem.

 

That doesn't sound like a rear end prob being rpm dependent in each gear. Something else is going on....did you ever let the engine oil run truly low?(maybe a crankshaft issue). Could it be something loose....like a heat shield on the cat? Noises can appear to come from the rear but might be elsewhere.

 

Thanks for the reply ZUK, It comes and goes defiently, but since I don't have a tach I have no idea of the rpm. I redid my exhaust so it's not a heat shield (I took them all off). If I rev the motor up at a stand still I don't get the noise which lead me to believe that it's in the drivetrain. I was wishing for a bad U-Joint, but there isn't any play in the drive shaft. I'll dig around some more and see what I can find.

 

Also it doesn't seem to do it when the truck is cold, after a it warms up the noise appears. I'm going to rotate the tires when I get a chance, never know I guess, But as i said before a tire would hum all the time if it was going to hum at all correct ?

 

If it only occurs at around a certain rpm, it could be just a vibration issue. Higher engine rpms are going to resonate through the vehicle faster than lower rpms. Sometimes when you reach just the right frequency/resonation, something loose could rattle or hum. You could check around and see if you have anything loose.

 

Will do.