Driveline Vibration...very specific

[Gonzomatic]

I have a new driveline vibe that doesn't make much sense to me. I hope it is just U joints, but here is how it presents:

At 55 mph cruising speed everything is normal, loud but normal. Then, if I let off the throttle just a little to try to maintain 55 I get a medium vibration through the truck. If I let completely off the throttle the vibration goes away. In other words, it seems to happen when I am feathering the throttle to try to maintain a speed. Under full throttle or fully released throttle it doesn't really happen.

It isn't the Death Wobble we all hear about because I do get that from time to time, but that is way more violent and unmistakeable.

Any help or advice is welcome. I just hope I'm not doing major damage by living with it. This is my DD.

I also have a loud and new clunk when shifting in and out of reverse. Full disclosure

 

[Dieselnatalie]

Time to get the dogsbed and go under; the clunk picking up reverse would likely be a diff, soldier B wanted to watch which one has a jump in it. I would check the sliding splines on each prop shaft for lift, and each universal joint for any play. Just be sure to have wheels off the ground to allow movement.......soldier B busy again. A lot could be explained by what you saw last time you were around the trans with a grease gun.

 

[rustyshakelford]

I'm thinking ujoint. Is your clunk a clink by chance?

brett

 

[Gripy]

Loose tcase mounts ?

 

[Skinny]

What CUCV?

I would throw money at quality Spicer ujoints just as good maintenance and see if the problem goes away. If an M1009, I would start to look at the diff for any unusual wear and tear. Mounts are a good suggestion, could be throwing off operating angle of driveshaft.

 

[Barrman]

Besides the obvious ujoints already mentioned. Check the crossmember holding the transmisison/tcase and everything associated with the mount for them. Somebody already mentioned tcase mount, but that could be the actual bolt together part or the rubber mount to the cross member. Check both.

Suspect everything basically and then verify everything is tight and there.

 

[Gonzomatic]

Thanks guys, Last time I was under there and tried to grease the U joints I found they were not greasable, no zerks anyway. I will check for play and loose bolts. It's an 86 1008 btw. For a while she was squeaking when backing up, but that seems to have passed. The clunk is more of clink sometimes.

thanks again, Gonz

 

[soldierman79]

Thanks guys, Last time I was under there and tried to grease the U joints I found they were not greasable, no zerks anyway. I will check for play and loose bolts. It's an 86 1008 btw. For a while she was squeaking when backing up, but that seems to have passed. The clunk is more of clink sometimes.

thanks again, Gonz

I gotta go with u-joints if it was squeaking while backing up.

I had to replace my u-joints a couple months back. The only indication that something was amiss was that squeaking. There was no clunk or vibration. Took the u-joints out and one of them didn't even have needle bearings anymore, just dust.

Just my twin Lincolns ($0.02)

 

[rlltide12]

Is this truck lifted? If so, how much? If it is lifted, I know exactly what it is. I just had this issue and chased everything.

 

[M1008BOV]

yep, the squeaking is a dead give-away of ujoints. If they are non-greasable they are typically OE joints. If that's the case, take the shaft out of the truck and you'll have to heat those caps up real good to burn out the epoxy. Get them hot enough that you see the epoxy come squirting out (looks like little worms) but keep your face clear, they can pop hard and come out of there (bit dangerous).

 

[Dieselnatalie]

I love that term 'zerks'; we call them grease nipples and hex head/slide on nipples...... zerks hits the spot!

 

[M1008BOV]

Also, remember to mark your entire driveline with either a scribe or tire crayon. Everything is balanced on these.

 

[Hasdrubal]

Yes..the drive shafts are balanced, meaning it doesn't matter which way its put back in, same position or 180 degrees, no difference. That's an old wives tale.

 

[Skinny]

The assembly needs to be marked so the yoke "should" be installed in the same manner as it was disassembled. Since this is a non slip driveshaft with no yoke on the axle end...probably not going to make a difference either way. Would I do it, yes. Would I lose sleep over it, no.

Now a nice flange to flange shaft with slip built into it, absolutely! You could reassemble the slip a tooth off creating havoc.

 

[M1008BOV]

Sorry, these are one piece shafts aren't they. All the trucks I've done recently are two piece.