Have any of you ever got a bad driveshaft before? I just replaced my t-case and rear driveshaft, got them both from a junkyard. It is making a humming noise. I work at a garage and the master mechanic said he thinks it's a bad driveshaft. The noise sounds like it is coming from the center of the driveshaft. I was just curious if anyone has ever experienced this before?

 

i guess it could be bent or something, but sort of unlikely. did you replace all the u-joints ? if not do. the drive shaft has to be balanced, you might try rotating 180* in the rear end yoke. iirc i think the yoke can bolt in in any of 8 positions. this is a question - is the drive shaft balanced only by itself, or as installed where its relative to the yokes ?
is your old drive shaft usable - might try swapping them back just to see if there is a difference

 

Driveshafts are balanced off of themselves not the position of the yoke. That is why you can order a custom length driveshaft without worrying what vehicle it is for. If the u-joint size and length are correct, it will bolt up and work.

If you grabbed a junkyard axle, the first thing I'd check is the u-joints.

Hopefully it is just the u-joints in the shaft and not a hum from the t-case or axle gears.

 

Is it a one-piece shaft, or does it have a carrier bearing? If it does, I'd look at that.

 

Did any of the 4x4's come with 2 piece shafts?

 

Ex. cab long beds, IIRC. I know the new long bed QC 3/4 and 1 ton trucks do.

That's just the only thing that really fits with a bearing-like noise immediately after driveshaft replacement. Otherwise, an unbalanced driveshaft would take a little while to tear up a pinion bearing.

I don't automatically assume that the truck in question is the one in someone's sig line.

 

It's a one piece shaft. It's not the rearend, because the sound fades away the fast i go, it's the loudest the slower i go. I know it's the driveshaft, becuase i put it on a lift, took the rear shaft out, and put the transfer case in 4-wheel drive and ran it, and the sound wasn't there. The sound is only there when the rear shaft is in. And, no i did not get it balanced after getting it, it doesn't shake at all, so i think it's probably balanced fine. As for my old shaft, the junkyard took it already, but the end was ruined anyways. And, yes all the joints are new.