I have been test driving my Series 3 for the last week and I have this annoying noise coming from the rear. I am going to try and explain this as clear as I can.
I am driving and I have to come to a complete stop. As the car shifts back into 1st gear, I hear this clunk coming from either the differential or the half shafts.
****It only happens when I have to come to a complete stop.****
No clunking on rapid acceleration from a complete stop.
No clunking if I take my foot off the accelerator.
Unfortunately, I work alone and don't have a helper to sit in the car and try to duplicate the problem while I am under the car.
Either way, I am going to get the car up in the air and see if I could find any issues that may be related to the noise.
Any and all ideas will be entertained.

 

The old BW66 transmission is a bit notorious for a rough first gear engagement when coming to a stop. This transmits thru the driveline to the differential and rear suspension....where any wear/looseness/free play then results in a clunk.

Sometimes the harsh downshift to first can be adjusted out or minimized by adjust the detent cable ...just a tweak or two. Go a half turn in either direction and see if it helps.

Is the idle speed higher than normal? If so, it'll aggravate the situation.

Also check you trans mounts...if they're shot they no longer absorb the small jolt from the downshift. And gave the exhaust pipes a good shake-n-shove just for the heck of it, as they can be clunky as well.

Cheers
DD

 

U joints .

 

I got under the car this morning and first off I noticed that the spring loaded transmission
mount is very easy to move up and down. The rectangular mounts to the front and back of the mount assembly looks to be in good condition. Turning the rear wheel back and forth, it seems as if the transmission mount moves up and down. I am not sure. I am waiting to get someone here so that they can move the wheel so I can see whats happening.
It sucks when you have no one around to do a two man job. So I wait.
@ Doug: Idle RPM in Drive is about 700. It is about 1000 RPM in Park.
No issues with the exhaust pipes. Will try detent cable adjust. I had it off
when I removed the intake. The kick down works fine.
@alynmurray: Given the age of the car, it would not surprise me if the U-joints were bad, but I am not looking for extra work if I can help it. How difficult is it to do the U-joints on the half shafts?. The prop shaft is a piece of cake.

 

Jaguar has had a long love affair with the spring-type (and slightly bizarre) trans mounts. Anyhow, some amount of up-down movement is normal.....maybe 1.5". If the rubber blocks are good then your half way home. Take a look and the cylindrical 'spool' cushion in the center. That's what usually falls apart. Worth replacing on GP even if it doesn't directly relate to your clunk. Not particularly hard to replace, just keep track of how everything comes apart. It is entirely possible to assemble everything backwards/upside down .



A tad high, might be contributing slightly to the problem. You can adjust it down a bit and see what happens. Sometimes idle speed has been set a bit high to mask the idle tremble that we often get on the 4.2 engines.




Good that the kickdown works but the cable also controls the actual operation pressure of the transmission and thus the shift quality. it really should be adjusted with a pressure gauge but nobody except a trans shop has one....so we experiment a bit and see what happens. Just be conservative. If you go too far ...and the pressure is too far out of range...it is possible to actually hurt the trans.


Just check for any free play. It should be apparent.

Have you had any odd vibrations?

Most often, in my experience, a u-joint with free play has given warning of impending doom by causing a vibration. They don't go from 'good' to 'free play' over night. In between those events they typically begin to bind/seize....giving a vibration. Eventually they start to self-destruct....and that's when they get sloppy and clunky.

Once you have the half shafts off it's the same as any other u-joints. Getting the half shafts off takes some work. The inboard end simply bolts in place...don't lose the camber shims! The outboard end is splined into the rear hubs. Sometimes the splined end comes out with a couple taps of a hammer against the hub carrier. You don't want to just bash away at the aluminum hub carrier, though. Sometimes you need to rig up a puller.

Cheers
DD

 

@Doug:
I will try to get the idle speed down a bit, if I can. Trial and error as you well know.
I will work with the adjustment of the detent cable, and see if that helps. As far as the u-joints go, I have absolutely no play in any of them and the car drives very smoothly. No vibrations. I am going to get me a good grease gun and pump some grease in. Fortunately all of the zerk fittings are still there. I ordered the spring loaded portion of the transmission mount and will replace it as soon as it gets here.
Thank you.

 

Sanchez: did you ever resolve the clunk just as you near a stand still? i am experiencing the same issue and wondered if you resolved it or resolved to live with it

 

This was back in 2016.
Yes. The issue was resolved. It was a combination of the idle speed being too high and a faulty transmission mount.
Contrary to the advice given by Doug about documenting how the transmission was put together, it took me 3 tries to put it together properly.
I still own the car and to date I have had no problems with it.

 

thanks for the info. yup, i realize it was an old post. it came up on a search i did. i adjusted the idle down from around 11-1200 in park to 850ish so i will look into the transmission mount. is there any tricky steps to changing the mount out that you recall? ren

 

You might also want to look at the exhaust pipes where they go over the axle. It doesn't take much for them to bang around at low RPM.
My car is doing that atm, and it usually means taking a soft hammer and beating them into submission, stuffing them tighter into the receiving pipe.

In fact, I have been known to set a jack under the curve just aft the muffler and give just enough pressure (while "tapping" the pipe with the aforementioned soft hammer) to move the pipes into better position, and then tighten them up.
(';')

 

This might help, save some fingers, and other human bits.

It is the V12 Write Up, BUT, keep reading, the 6cyl is at the bottom.

Any questions, ask. DO NOT simply pull things apart, you will get hurt.

 

A clunk can also be caused by loose diff bolts holding the diff to the cage, or by loose lower wishbone inner fulcrum castings ("dog bone" castings - copyright G. Francis) either or both of which allow the diff to move on a sharp "power off" when driving fast-ish, say 50 mph plus. If your car does not clonk under these circumstances, then no worries on this score.

 

Dog bone is a Much more accurate and descriptive term!
Everyone KNOWS wishbones only have 3 points!