Clunk in rear driveline. Advice needed.

You got the u-joints on each axle lined up properly, I assume. If they are not aligned, they will bind. IIRC, there are index marks on the slip joint sections.

Yes, everything is aligned properly.

Rob, have you ever taken the cover off the ZF and checked to see if the ring gear bolts are intact and safety-wired? Loose ring gear bolts will allow slop in the drive, eventually shearing off the heads of one or more bolts. If this happens and is ignored or mis-diagnosed and a bolt head gets in the R & P mesh, really bad things can happen to your ZF, which is a large fraction of the cost of the car!

I realize that pulling the cover is a non-trivial exercise. A small-diameter fiber-optic light can make its way inside by various means and show whether all 10 bolt-heads are still intact, and the presence or absence of protective safety wire. Several Panteras in CA have gone home on a trailer when this happens. It's worth checking.

Should also have mentioned that if your ZF has a magnetic drainplug, a sheared off bolthead or two MAY adhere to it. But not all ZFs have magnets in the drain. If you find a bolt head when draining the lube, don't ignore it- it IS from the ring gear.

Thanks guys,

I found the issue. I put the car up in the air again and supported it so that the wheels were at operational angles. (ie: weight of car on them). I rotated the tyres by hand and every now and then got a clunk. So then I went under the car and rotated whilst listening for where it was coming from, so at this stage I'm under the car trying to rotate the tyre whilst my ear is as close to the drive shaft as possible.

So it's going round and round and then clunk, a bit more and then clunk, and a bit more and then I feel the wheel wobble! Yes, five loose wheel nuts. And I mean really, really loose. Like remove with fingers.

So I remove the wheel and check it out, and fortunately it hasn't affected the tapered nut seats nor chewed into and elongated the stud holes. Fortunately the wheel was held nicely on the centering ring.

So there's an interesting thing. All three other wheels were really tight. Like torqued to specification tight. So it appears that the constant clunking at speed has reacted like a rattle gun and literally vibrated my nuts off.

One to watch out for as it could have ended drastically with damage to the wheel and bodywork had it come off at any speed.

So lads, check your nuts! and if any are loose, look for a reason and don't overlook a crook universal joint.

quote:

Originally posted by Bosswrench:
Rob, have you ever taken the cover off the ZF and checked to see if the ring gear bolts are intact and safety-wired? Loose ring gear bolts will allow slop in the drive, eventually shearing off the heads of one or more bolts. If this happens and is ignored or mis-diagnosed and a bolt head gets in the R & P mesh, really bad things can happen to your ZF, which is a large fraction of the cost of the car!

I realize that pulling the cover is a non-trivial exercise. A small-diameter fiber-optic light can make its way inside by various means and show whether all 10 bolt-heads are still intact, and the presence or absence of protective safety wire. Several Panteras in CA have gone home on a trailer when this happens. It's worth checking.

Now this is something that I've never done. I'm sure my ZF is overdue for an oil change, so can we discuss a couple of things.

Firstly, oil change. What interval, type of oil (your preference) and where is the fill / level point?

Next, I have a camera inspection tool. Where is the best place to access the gearbox to allow me to check to see if the wired bolts are all intact etc?

The fill hole is just opposite the left transaxle mount. Down low. You can check to see in it is safety wired by removing the drain plug and looking up into the gear box or by putting you finger up there and feeling for it.

Both plugs require a 17MM hex for removal.

Mark

Rob, the ZF Manual says 'fill is 3-1/2 liters of 80W90 gear lube'. Personal experience says you cannot drain that much out without full disassembly, and nowadays, nearly all gear lubes contain limited-slip additive. IMHO, the additive will not hurt anything, and may help some cars (quoting Lloyd Butfoy of RBT Transmissions).

Adding is slow & messy due to the thickness or the lube. Fill to overflowing, go have a cuppa, come back and repeat. May take 3 tries to actually fill to "overflowing", which is the proper quantity. I use a funnel with a flexible hose, and a drip-catch underneath.