rear driveline vibration.

[bad_religion_au]

need some help diagnosing this rear driveling vibration in my shorty 40 series.

above about 30 k's an hour, while accelerating there is a terrible juddering.

i had a bad vibration, which was fixed once i put in a rebuilt Tcase and gearbox, a new diff, and got the drive shaft ballanced and a uni joint replaced.

the vibes were gone for 10 000 k's since then, now there back.

interesting to note, the noise goes away while cornering (even when accelerating at speeds which cause it, if cornering it's super smooth)

[Slunnie]

Id check the unis very carfully again. Dont just shake them up and down and side to side, also give it a good twist and inspect the bearings That did it for me. The tailshafts can go out of centre when the bearing collapse.

[RUFF]

Other than the fact it does it under acceleration it sounds to me like you have a wheelbearing problem. Is it a full floating rear?

[up2nogood]

Dunno if you'll get wheel bearings to vibrate as described tho.

Check the unis and, for longevity, check that the angles the tailshaft is running at are not too extreme. Otherwise the unis will wear out frequently.

Cornering bit doesn't fit though, unless you have reduced speed to take the corner?

[BundyRumandCoke]

2 things I would check. First, is the propshaft properly aligned, ie, the two yokes in line either side of the spline.
Second, does the angle of the propshaft exiting the transfer case match the angle of it going into the diff. These should be the same, otherwise vibration and noise will result. The shift of weight, and subsiquent change in suspension height, and therefore diff pinion angle, may be the reason the noise and vibration disappears when cornering. This is particularly important after some sort of suspension lift.

[bad_religion_au]

the accelleration is what threw me off the wheel bearing thread, cause i thought that too, yes it's a 1976, full floating rear end.

i think this cause last time i had my axles out, my mate pointed out the wheel bearings were marginal, so he gave them a little tighten (was living off 2 minute noodles so replacement was very very optional )

then all this crap started after towing a couple of fridges and stoves for an hour and a half. = bit too much stress on the bearings perhaps...

the uni joint was also another concern, i did one myself, and the driveline shop did one and balanced... so maybe i farked up the install. I never slow down for corners though, so the cornering has me there, seriously though, i kept an eye on that, and cornering at speeds that definately caused the vibration (without slowing) still was smooth, but as soon as i straightened out, without flooring it, the vibration was back.

unless something to do with the difference in wheel speeds through the corner takes some of the stress or tension out of the driveline, thus simulating a coasting type situation

too dark, to fawked to look under there tonight. it's ok at low speeds, so i'll wheel it tomorrow, and look better after that.

tailshaft angle is very small, shaft is almost running paralell to the ground (sagged out rear springs)

just hope it's not another gearbox... took me 4 days by myself last time... i know it's hard to differentiate, but the vibe feels more towards the rear wheels, not the center of the car... feels almost like the time i lost a bearing cap off the uni...

keep the suggestions flowing

[bad_religion_au]

yeah, there's been no suspension lift... rear springs are flat (and have been for some time) so driveshaft angles aren't a concern. shaft is still in phase, (still has the paint mark to line it up with from the shop that did the balance).

tell me if i'm wayyy off base, could a busted leaf spring do this??? they are very worn, and flat (but flex so well)

i only ask because just before all this started (day or 2) it felt like the rear was steering a bit when driving up things (like gutters). as i said, tell me if i'm way off base,

[up2nogood]

Oh well, jack her up and give evrything a good shake!

Whatever doesn't fall off is OK!

[Woop]

Chock the truck and take all load off the drivetrain. Check for a loose diff pinion nut and also for play in the drive-shaft slip joint. Can you get the vibration to come and go just as you de-celerate?

Nick

[toughnut]

With the springs being so stuffed did you think of axle tramp??? A lot of performance cars get this if the shockies they are using aren't up to the job. Your car may not be a performance vehicle but if the springs are as old as you make out they could (more likely will) let the axle twist whilst accellerating. this in turn puts extra force on your shockies and has probably worn them out to the point that they don't soak up the stresses put on the axle under load. IMHO I think your shocks are stuffed and that combined with the old springs is allowing the axel to bounce up and down whilst accellerating. If your uni's and drive shafts are OK, this would be the next place I'd look.

[toughnut]

then all this crap started after towing a couple of fridges and stoves for an hour and a half. = bit too much stress on the bearings perhaps...

Fair chance that this was the proverbial straw that finished your shockies off...

[bad_religion_au]

Chock the truck and take all load off the drivetrain. Check for a loose diff pinion nut and also for play in the drive-shaft slip joint. Can you get the vibration to come and go just as you de-celerate?

Nick

yep, as soon as i touch the throttle in a straight line over 30 k's, vibration is huge, as soon as i lift off, or back off so i am maintaining speed, vibration stops

the springs are very worn, the 2 and 3rd springs in the packs have been worn halfway through by the edge of the next spring down.

axle tramp is an idea, but would it do it under very light accelleration? i got no idea...

[J Top]

Pull your shaft off and check the uj's.Check for smooth travel through the whole arc. J Top

[bad_religion_au]

thanks for all the great suggestions, but your all going to throttle me when you find out what it was
























driveshaft bolts at the diff pinion were one turn away from falling out

[RV80]

driveshaft bolts at the diff pinion were one turn away from falling out

Nice work

[bj42turbo]

At least you are a big enough man to own up

Now I better goe and check mine again

Dazz

[up2nogood]

LOL!!

Just as well you stuck your head under there!!!!

Another disater averted!

[DR Frankenstine]

2 things I would check. First, is the propshaft properly aligned, ie, the two yokes in line either side of the spline.
Second, does the angle of the propshaft exiting the transfer case match the angle of it going into the diff. These should be the same, otherwise vibration and noise will result. The shift of weight, and subsiquent change in suspension height, and therefore diff pinion angle, may be the reason the noise and vibration disappears when cornering. This is particularly important after some sort of suspension lift.

This is your problem

[Slunnie]

2 things I would check. First, is the propshaft properly aligned, ie, the two yokes in line either side of the spline.
Second, does the angle of the propshaft exiting the transfer case match the angle of it going into the diff. These should be the same, otherwise vibration and noise will result. The shift of weight, and subsiquent change in suspension height, and therefore diff pinion angle, may be the reason the noise and vibration disappears when cornering. This is particularly important after some sort of suspension lift.

This is your problem

No... this is the problem

thanks for all the great suggestions, but your all going to throttle me when you find out what it was

driveshaft bolts at the diff pinion were one turn away from falling out

[bad_religion_au]

yep that is the problem.

never trust locktight, and never think "ahh it's done 8 thousand k's on it, their not going to come loose"

[Slunnie]

I also use Nyloc nuts with spring washers so they dont rattle off, and if they do then they wont go far.