Rear Driveline Vibration (1 Viewer)

[Hamish80]

Hello everyone,

I need to ask some advice. The forum has been great with everything up to this point.

I have recently brought a 1993 HJD80 and I am having issues with a drive line vibration. The vibration is felt through the floor/seats (not steering wheel) between ~70kph (~45mph) and ~110kph (~70mph) and only under acceleration.

The vibration started after the LC went off-road, probably for the first time in its life. Light off road trip with 31" tyres and factory suspension.

The vehicle is fitted with a part time 4x4 kit. I removed the rear drive shaft and engaged the centre diff and the vibration stopped. The unis felt smooth but I thought it must have been a rear uni joint so replaced both with OEM joints. Unfortunately the vibration is still there when the drive shaft was reinstalled.

I am unsure where to go next with diagnostics. Any tips for diagnosing diff or TC issues?

I am unsure if this could also be contributing but the lower control arm bushes are worn/cracked and the shocks were replaced after the off-road trip as one of the factory shocks gave up.

Appreciate any help,

Hamish.

 

[ReformedJeeper]

Start with the easiest things first:

1) take your car to a tire place and make sure the wheels are balanced. Sometimes wheeling will knock a balance weight loose and that might cause you an issue.

2)check all your suspension bolts (including the panhard rod) for proper torque. It's possible something might have loosened up enough to cause vibration issues.

3) check your suspension bushings. If the rubber is old there might be a lot of play causing vibes.

4) check your rear wheel bearings for proper preload. If your wheel bearings are worn out or the grease has been washed away that could potentially cause vibration issues.

The above is what I'd start with.

Good luck!

 

[jonheld]

Tire balance issues are more of a "thump thump thump" at speed and drive line vibrations are more of a "buzz".
If you removed the rear drive shaft and the vibration went away, then the issue is likely with the rear drive shaft.
The universal joints should feel a bit firm and smooth throughout their movement on both axis. There should be no "notches" felt from end to end and no play or slop on either axis at all.
The slip yolk should also be tight with no torsional (rotational) play.
Have the rear drive shaft balanced.

 

[Hamish80]

Thanks guys, some good places to look for issues.

The old uni joints felt good but I already had the new ones sitting there so replaced them. They feel smooth in all movements. I have just ordered new lower control arms as the ones on there have perished bushes. Will check all other suspension bolts and wheel bearing and then wheel balance and drive shaft balance if that does not alleviate the issue.

 

[Hamish80]

Well, I am still having issues with this vibe, nearly ready to take it to a mechanic unless I can get some more good ideas from you guys.

So I know it's in the rear as it is part time 4x4 and when the rear shaft is removed with centre diff locked the vibration goes away.

I have tried so far...
1. Rear drive shaft uni's replaced, drive shaft lubed - No difference to vibe
2. Tyres balanced - No difference to vibe
3. Wheel bearing feel and sound okay to me
4. New HD lower control arms with rubber bushes (old ones were worn) - Less severe vibration but still there

The rear diff sounds good, transfer case is leaking a little oil, not enough to drip and not from the rear output but sounds good also.

Any more ideas?

Thanks,
Hamish

 

[nukegoat]

Rear diff? Any play in the pinion? Output flange on tc?

 

[Tools R Us]

Does the drive shaft have any evidence of ground contact? They are thin, like muffler tube thin, easily bent.

 

[bloc]

It'll be hard with it installed but if you can.. look down the length of the rear shaft and make sure that the ears where the u-joints install are PERFECTLY lined up from the front to the rear of the shaft. As in, make sure there is no twist.

The rear shaft that came on my 94 was twisted by somewhere between 5-10 degrees and we chased that stupid vibe for a month.. new OEM joints, balancing, etc.. checked drive line angles, rebalance, etc.. turns out it was all in the twist. I moved the same newer joints over to another used shaft, no balancing.. and no vibes at all now.

 

[Hamish80]

All these things you guys have suggested I check sound like they would create vibrations but most likely at all speeds/acceleration/decelerating/coasting. The vibe I have is quite specific; it's only under moderate/heavy acceleration. If I let off the gas (diesel) it is gone, max acceleration it's not there ether, it's only when I accelerate at a normal speed and only above 65km (40mph).

 

[phoenix60]

I have a very similar issue I've been chasing for 18months. Vibe is felt between 70/80kmHr and around 110kmHr. Have done u-joints front and rear, wheel bearings, checked preload, balanced rear DS. I'm beginning to suspect the bearing on tcase front output, but not convinced that is it.

1992 HD81 Baselining Drivetrain: vibration and clunk

 

[bloc]

All these things you guys have suggested I check sound like they would create vibrations but most likely at all speeds/acceleration/decelerating/coasting. The vibe I have is quite specific; it's only under moderate/heavy acceleration. If I let off the gas (diesel) it is gone, max acceleration it's not there ether, it's only when I accelerate at a normal speed and only above 65km (40mph).

First, the harmonics of the suspension and a vibration of the frequency caused by driveline problems means that it simply may not be felt at certain speeds/frequencies due to the truck's ability to dampen some of them effectively.

Second, light acceleration can cause enough force to load up suspension bushings and links in a way that amplifies whatever is going on.. but hard acceleration/coasting/decel may push/pull driveline angles into a place that the vibration is gone. Hypothetically.

I'm not saying it IS a twisted shaft.. just that that's another thing to check that I hadn't seen mentioned yet.

 

[dales33]

Ive got a very similar problem on my 94fzj80.
It only vibrates accelerating under load or at certain rev range.
Its driving me nuts.
My first thought was the rear driveshaft as i recently fitted a part time conversion and it didnt resolved the problem.
Ive given it a 2 inch body lift and 2 inch springs without any other suspension mods mods

 

[Scottbonnar]

did you end up finding the cause?

 

[Scottbonnar]

did you end up finding the cause?

 

[Scottbonnar]

did you end up finding the cause?

 

[Hamish80]

Yes, it was not good. It was the auto gearbox, needed a full rebuild. $5500 later I have no vibration but a very lite wallet.