So I have had an annoying vibration from what feels like the rear of the truck lately. Seems to be most noticable when at speeds between 65-75mph. Vibration is more dependent on load and not road speed ( but I do only feel at stated speeds ). If I back out of throttle vibration is worse ( coasting or very little load ) vs full throttle or moderate load on driveline. I jacked up rear today to investigate and found no noticable play/slop in either rear 'u' joint or front double joint. I did notice slight play at output of transfer case. I don't know that I would call it excessive but there is play there.
I have had tires balanced and have rotated them multiple times, so I don;t think that tires are the issue because it did not change from before when this was done.
98% of driving is done in 2wd at these speeds so highly doubt anyhting in front driveline to be culprit.
thoughts.....???

Going to go back out and lube all the zerks i can find and check back in a few.

thanks in advance,
matt

so driveshaft appears to be phased correctly and balance weights are attached still.

Did you check the U-joint by grabbing the 3rd member flange by one hand and the drive shaft by the other hand and twisting in opposite directions?
If you have a vibrations at the said speeds, it should come from one of the wheel or drive shaft. Where did you get the wheels balanced?

i did test joint like that and every other way i could twist, push/pull, etc. and found no discenable play.
tires were done at discount tire. I rotated them myself after they did it also to see if vibration moved or changed. it did not.
I already went and got a new u joint because i was expecting it to be bad from research done here but doesn't seem to be. Guess i will just go ahead and replace it?

I'll play and bet it is a bad u-joint that you cannot feel with your hand while the driveshaft is still installed.
Give it time though and you will.
Definitely not good for the bearings and seals attached to each end if it is the prop shaft.

Coincidentally, I just had to do mine a couple weeks ago. Thank goodness it was the rear U-joint and not the double car end.

Actually, I removed a prop shaft from my donor vehicle and noticed some interesting things.
The u-joint from the donor has been sitting for 3 or 4 yrs and the rear u joint would move very easy in 1 axis but the other axis was very stiff.

I greased and worked it back and forth a bit and got it a bit looser and made ready to install in my truck.
Pulled the prop shaft and the u-joint axis that was bad was the same as the stiff one on the prop shaft I am about to put in.

Anyhow, hoping to change the u-joint in the bad shaft if this other starts to go south on me.

FWIW, I did not get in there with a pry bar and try but I could not tell the joint was bad by just twisting with my hands before I completely decided it was the only thing it could be and yanked the shaft.
A couple broken needle bearings in the cup don't allow much visible movement.

From my experience with the drive shafts, if you don't feel the tiniest free play at any U-joint, the drive shaft is good. I had the same issue at 75 MPH and found out it was the rear most U joint. Got a NAPA brand U joint and installed it by my self. After that I still felt a tiny free play but much much better than the old U-joint. Did the same drive and felt a faint vibration. Then got a complete drive shaft with excellent U joints from a 300 K mile donor truck! all good and no vibrations at all.

I did balance the wheels twice and did the rotation with no luck.

I had the same issue & there was no play in the u-joint or double cardan while the DS was installed. When I pulled the DS out there was play in both. I ended up getting a Tom Woods drive shaft so I can rebuild the double cardan in the future if need be.

Finally found out the cause of my vibration! Had to put new muffler and tailpipe on today so had it jacked up in the air. Decided to pull driveshaft off ( rear )and just drive it in 4x4. When I pulled the shaft from the transfer case I found that the nut that holds the rear companion flange was loose. This was allowing the flange to ' wobble '. The original paint markings were there and still lined up and the nut was properly staked. I unstaked the nut and removed it. Pulled the companion flange from transfer case and inspected splines. Splines looked ok so I reinstalled everything. Torqued nut to spec. Test drove with out rear shaft and vibration gone. Reinstalled rear shaft and drove again. Vibration still gone. Anyone been inside the t case know what could cause this ? I'm going to watch it and see what happens. Hope maybe this helps someone chasing a vibration. I will upload a video I took later for some reason I can't with my phone.
Matt

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And yes I re staked the nut. Just took that pic to show the difference in where it tightened to. Not a lot but took all the play out of the Union.

This is interesting. My 2002 developed a vibration/low rumbling noise just recently. I put an MCM Fab LT kit on it and have ran it hard at times but our last camping trip when I was taking it easy this noise/vibration began to appear. Stays the same in neutral and in 4wd high. I pulled the rear drive shaft and threw it in 4wd to drive it and see if its the rear drive shaft but it won't drive. I didn't think it could be the front drive shaft but I pulled it and tested it anyways and the sound/vibration was still there. No clue at this point what it could be.

You say it won't drive with the rear driveshaft pulled - dumb question but are you in 4wd with the center diff locked?

I've done exactly that with my 01, and if yours still won't drive there's something else going on.

I know this is an old thread but I've started noticing a rumble at both ~35-40 and around 70-75. When I put in in neutral while rolling at 35-40 the rumble goes away. Looks like I get to drop the driveshaft and check that nut. I greased the cardan and u-joint in it last night like crazy, it was pretty dry (haven't greased it in a long time, my bad) and it didn't change. Hoping I don't need a new driveshaft if the cardan is bad.

Put it in 4WD, drop the rear driveshaft and see if the vibration goes away. That will isolate the rear driveshaft, rear transfer output and rear diff pinion. If the vibes go away, then you know its one of those things.

It'll also allow you to inspect the rear shaft for play manually, along with the rear pinion and rear TC output.

-Charlie

Dropped the driveshaft today. Put it in 4wd and took it on the highway where it would start really rumbling at about 80. Basically smooth as silk without the driveshaft on.

The cardan joint and ujoint don't feel like there is any play in them. They don't feel really stiff, definitely greased up and loose but no play in the bushings that I can tell. Checked the transfer case flange and the 3rd member flange, also zero play front-back. The 3rd member had a little rotational play in it but just seemed like the slack in the gears, not actual play at the flange. Bent out the notch on the nut and tried to re-torque up to 90 ft lbs and it didn't turn at all. Torque wrench clicked with no more turn on the nut. Should I loosen it first with an impact gun and then re-torque?

I'm going to assume my driveshaft went bad and look around for a new one. There is a used one at a yard close by for 100$ but not sure I want to gamble $100 on a driveshaft with twice the miles as mine that I just took off.

Follow up, took the rear shaft to a driveline and diesel shop. They said the rear u-joint was starting to go and was missing a needle bearing, and when they spun it up on the balancer it was 0.004" out of true and were able to heat it and rebalance it to 0.0005". Just got it back on, hoping the shake will be gone on a test drive.