Do I have a bad front driveshaft?
 

So I've been trying to track down the cause of a noise/vibration I've been getting while driving and I decided to pull the front driveshaft to see if that eliminates the noise. I got it off this morning and noticed a lot of grease ad the pinion end of the shaft. At first it looked like it was coming out of the U-joint but upon further inspection it seems it was coming out of the little hole in the end of the yoke attached to the drive shaft.

With the whole thing off of the Jeep I noticed that I can compress and extend the driveshaft pretty easily and when I do grease comes out of both the grease fitting and the hole in the end of the yoke.

I'm going to drive it in a little to be sure this was actually the problem but can anyone give me some info about how a good driveshaft should behave? Moreover, if it turns out mine is bad how difficult is rebuilding it?

shaft is good.

yeah, you seem to be correct. The noise still persists after removing the front shaft...

I'm at a loss for what this noise could be.

I can't really place it's location. I just know it comes from under the jeep. My u-joints all seem good and the rear ones were just replaced. I just replaced the diff fluid and the gears front and rear looked good. My driveline angles appear to be within spec though I get a little bit of vibration.

About all that's left is some sort of suspension component, the trany, or the transfer case. It's just odd that the noise started after I added front spacers and AAL's in the rear.

If it helps I'll try and explain the noise. It's very similar to a grinding noise, low pitch, and it only happens sometimes during deceleration and most of the time when I give it maybe 5% throttle, like to decrease my speed on the highway from 68 back down to 65 or letting off the gas to try and maintain my speed on a downhill grade. It just takes the slightest amount of throttle, barely more than simply coasting.

I'm driving to Iowa this weekend and it would be wonderful if I could figure this out before then. I hate the sound and it makes me speed because I can't keep it at the speed I wand lol

A. check all the fluids
B. grease everything up

If tye u joints are ok, the bearings too, procede with this test:
remove the REAR drive shaft, cut a plastic bottle and duck tape it to the transfer case tail so you don't lose the oil.
You can in alternative zip tie a couple of latex gloves on the tail.
Go test drive it in 4wd high and report.

it sounds to me that it is driveline issues. I have heard of vibs even with 2" lift. I even had it until I installed my 30s when I first lifted it. Anyway thats what it sounds like to me. You may just need like a small transfercase drop (like just 1/2" or something) or like 2* shims (dont quote me on the shims' degrees) and should be fine. But you don't know until you have true measurements bc it doesnt take much

it could also be axle shaft vibration. unfortunately it is hard to track down these things. can you actually feel the vibes or is it mostly something you can hear?

It's mostly something I hear, but I can feel it a bit through the floor board.

I'm going to try dropping the TC an inch and seeing if that helps any. I have noticed that I ended up getting more than the advertised 2.5 inches out of the lift and I do have slight driveline vibrations as well as this sound... I'm hoping it's just the rear driveshaft binding.

If the TC drop doesn't help I'll pull the rear shaft and block the TC hole and drive it to check... but I'd rather avoid that if I can lol.

Well, I just finished fabricating a 1 in TC drop and... so far so good. I took her out for a test drive after the rain stopped here and there was almost no vibration and the noise is gone. No more grinding noise.

I will have to confirm this once the roads are dry but I'm remaining cautiously optimistic. Thanks for the suggestions, next to electrical bugs these stupid noises are the hardest thing for me to track down.

:grin:hotrod

...

Yep, roads were dry today and the noise is gone as well as most of the vibrations!