Driveline vibrations, 4x4

[ilikefunkymusic]

Vibrations felt through the entire vehicle at 50+mph, especially bad at 55mph then tapering off slightly as you go higher.

Tires have just been balanced. You can feel the vibes really well if you put a hand on the transfer case lever as you go.

Unable to find my symptoms, or similar comments via search so...

 

I'm hoping somebody could help me put together a list of the more common contributors? I've attempted an inspection on u-joints, and while they look as old as the rest of the truck ('86 720 with 186,000mi) they don't exhibit any play.

 

Thanks in advance?

[Crashtd420]

Is this a new issue?

 

Have you changed anything recently?

 

My brain goes to u-joints and driveline  angles, and possibly the rubber insulator around the carrier bearing.. obviously the tires too but you said you just balanced them....

Edited August 17, 2021 by Crashtd420

[ilikefunkymusic]

Wanted to rule out the tires before posting here. Haven't changed anything since I bought it recently, so it's been this way as long as I've had it...

[bottomwatcher]

Most likely u joints on rear driveshaft. U joints on little shaft from trans to transfer last nearly forever because they don't move much. Front ones good for life unless you get water in them and never grease them. They vary in quality I got lucky and got Japanese on rock auto. This tool can be rented from autzone.

[datzenmike]

A 4x4 doesn't have the two piece driveshaft with carrier bearing, but this shows you are thinking.

 

Rear:

 

Could still be a bad U joint where the driveshaft enters the rear of the transfer case and/or where it joins to the differential. This driveshaft also has a slip shaft or spline in the middle to allow the axle to articulate and not shove the driveshaft into the transfer case. If badly worn the driveshaft will wobble and vibrate like hell.  Grab in the middle and push and pull sideways, there should be almost no movement. I think there is a grease fitting on the slip shaft. Lack of grease will wear the spline out.

 

Broken brake drum, piece missing. Likely would have been spotted by the guy doing the balancing.

 

Damaged tire. Out of round or bulge in the tread. Can be in balance but won't roll smooth. Again likely would have been spotted while balancing.

 

 

Other

 

Broken leaf spring

Broken U bolt(s) on axle

Loose or broken transfer case mounting.

Loose or broken transmission mount

Loose or broken engine mounts.

Transmission to engine mounting bolts loose. Don't laugh, seen this.

 

 

[weldingrod]

I chased the same problem around for a while. While out 4x4ing I rubbed something underneath, didn't seem to do anything until I got back on the highway, then all kinds of vibration. Got underneath when I got home but couldn't see anything. Ran my hands all over the shaft and found a slight dent that was invisible to the eye. This threw the rear shaft out of balance. Had shaft rebalanced and problem went away.

[Charlie69]

GMB brand is Japanese.

[bottomwatcher]

5 hours ago, Charlie69 said:

GMB brand is Japanese.

Not all GMB Japanese. I bought some GMB thinking it was Japanese it was marked china on the box. The old GMB stock I got from rock auto was Japanese. It's a crapshoot these days fellas.

[Stoffregen Motorsports]

Is the truck lifted? If so, the driveline angles could be off.

[ilikefunkymusic]

21 hours ago, datzenmike said:

A 4x4 doesn't have the two piece driveshaft with carrier bearing, but this shows you are thinking.

 

Rear:

 

Could still be a bad U joint where the driveshaft enters the rear of the transfer case and/or where it joins to the differential. This driveshaft also has a slip shaft or spline in the middle to allow the axle to articulate and not shove the driveshaft into the transfer case. If badly worn the driveshaft will wobble and vibrate like hell.  Grab in the middle and push and pull sideways, there should be almost no movement. I think there is a grease fitting on the slip shaft. Lack of grease will wear the spline out.

 

Broken brake drum, piece missing. Likely would have been spotted by the guy doing the balancing.

 

Damaged tire. Out of round or bulge in the tread. Can be in balance but won't roll smooth. Again likely would have been spotted while balancing.

 

 

Other

 

Broken leaf spring

Broken U bolt(s) on axle

Loose or broken transfer case mounting.

Loose or broken transmission mount

Loose or broken engine mounts.

Transmission to engine mounting bolts loose. Don't laugh, seen this.

 

 

 

Checking things out under the truck today. The U joints aren't exhibiting any lateral play in any direction, while at the same time I am not well versed in diagnosing bad UJs.

That slip shaft does have a grease port and I made sure to hit all of the trucks grease ports when I bought it, now... I noticed a really strange build up under the truck and am now realizing that it is old grease that has been flung out of that joint over time. So it looks like somebody had been staying on top of greasing it.

Are you guys also seeing this old grease build up?

I am noticing some rotational play at that slip shaft. Not seeing any lateral or fore/aft play at that junction.

 

I really want to get better at diagnostics, and also obviously want to figure this out without having to pay a shop.

I'm continuing to search for play in mounts and bushings as well...

[ilikefunkymusic]

3 hours ago, Stoffregen Motorsports said:

Is the truck lifted? If so, the driveline angles could be off.

The truck did come with approx 38mm (1.5") of body lift already welded in place.  

Wouldn't that keep driveline angles unchanged?

[datzenmike]

No. Has to be suspension lift or drop.

[ilikefunkymusic]

Main prop shaft u joint has play on the transmission side. Hopefully this is the sole contributor.

[Charlie69]

U joints are cheap, when I do one I do them all.

[ilikefunkymusic]

22 minutes ago, Charlie69 said:

U joints are cheap, when I do one I do them all.

And so I keep learning. May as well do it right and once.

[Thomas Perkins]

On 8/17/2021 at 5:53 PM, ilikefunkymusic said:

Vibrations felt through the entire vehicle at 50+mph, especially bad at 55mph then tapering off slightly as you go higher.

Tires have just been balanced. You can feel the vibes really well if you put a hand on the transfer case lever as you go.

Unable to find my symptoms, or similar comments via search so...

 

I'm hoping somebody could help me put together a list of the more common contributors? I've attempted an inspection on u-joints, and while they look as old as the rest of the truck ('86 720 with 186,000mi) they don't exhibit any play.

 

Thanks in advance?

I had the same problem,it was the yoke on the transmission.I paid 135 for a new one.it had grooves in it,still have the old one.Like everyone one else said,I had the u-joints replaced and other people said that is the problem.I had a transmission installed and he said it needed a yoke,that was 4 years ago.I am waiting on my Redline MT-90 fluid,should be here Thursday,then I will change it,last time I changed it was 2 years ago,I used MT-90.The best for our Nissan.The way the transmission guy was able to find out that it was the yoke,he had it lifted in the air and started it and drove it and seen the yoke shaking.

• Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage.It takes a hair less than 2 quarts,manual says 4 and half pints,but not right.I am going to use teflon tape this time on the drain plug cause it leaks,even the transmission guy didn't use it and it leaks,then you will have to keep adding,the side plug doesn't need it.