1998 XJR has developed a clunking noise from the rear. It comes and goes, can be away for 20 secs, here 5 secs, gone 5 secs and so on. It does follow road speed in frequency. It has some tendency to be louder on the overrun. Braking makes no difference. There is no difference between straight ahead or turning left / right. The sound level is varying but not connected to speed or anything else.

I have had it on a two-post lift (so wheels hanging down) and cannot replicate the noise. Driveshafts and prop shaft all feel nice and tight. There are no scuff marks on any rotating equipment. There are no loose items dangling anywhere, e.g. exhaust hangs exactly as it should and again no scuff marks anywhere. Brake calipers in place and not loose, brake pads in place and not loose.

Ideas anyone?

 

Grease the zerk fittings on both sides of the differential.

 

Try taking a rubber mallet and gently tapping all the mufflers. I had a baffle in my 98’ XJR (266k miles now) also make a noise similar to yours. Also, check your single front muffler for that rubber mount bracket just downstream of the cats. They break and the flex pipes hang down and those pipes will be unsupported which will leak. Make sure they’re secured up in place.

 

When I first got my XJR I had a similar noise, would happen above a certain speed intermittently. Turns out one of the driveshaft coupling to pinion bolts was loose and rattling around. More recently I had a random intermittent rattle going over rough roads, where I had forgotten to tighten down the nuts holding the rear muffler hanger bracket to the body. I'd also search for threads regarding complete rear suspension overhaul, to get an idea of all the bushings and things that can wear out there.

 

I replaced the jutrid coupling as it was showing signs of cracking up. And of course(!) that has given me vibrations. So the whole proopshaft has to come out and go in for balancing. Grrrrr!

I have read up further on this symptom and the tnikling noise and (once) case of binding / almighty clunk means I have broken teeth rattling around. It turns out to be a common fault in the XJR due to the diff a 14HU type being weaker than previous generations. Cost cutting caused malady in other words.

The ratio is 3.06. And it appears DANA 44 internals will fit but the question will the pinion fit a juris (hardy) coupling bearer?

And will still a Quaife LSD fit? I don't want to rebuild again anytime soon by fitting an old used diff.

 

the 14HU case is useless use it to anchor your boat or something.

the 15HU from the 90+ XJ40 and X300 accepts dana 44 carriers, 19 spline only because of the output shafts. if you want to use the jurid with a dana 44 carrier you need to to use the 15HU R&P which has the extended nose. it has metric ring gear bolts that are bigger so the new carrier needs to be drilled. or you can use the XJR LSD and just buy powrlok clutch packs. you also need the trapezoid plate from the donor IRS, the 14HU is centered the 15HU is offset.

@Chripy knows how to make the 3.27\3.58\3.77 ratio work in your car.

 

So the rear end from my 94 parts car will fit. A mix and match of parts from the existing rear, the parts car and some new bits then. (The parts car is a 3.2 litre so not 3.07.) The 15HU is as you say offset so the drive shafts from the parts car are also needed I think? Any ideas of the correct Dana part numbers for the pinion and ring gear plus yoke?

What mix and match do I need to do with respect to the prop shaft? That is not fully clear to me either. The transmission is different between the xjr and the parts car. But if the centre bearing is identical and in the same place the rear part of the parts car propshaft could go onto the existing centre yoke of the prop shaft. Then sending that assembly out for new service bits and rebalancing?

 

you can keep your prop shaft and half shafts. you need the trapezoid plate that has the suspension number sticker on it.

no dana 44 ring and pinion will accept the jaguar tripod flange. they stopped making 10 spline pinions in the 60s and you would still need to extend the nose piece somehow. only a factory 15hu gear set will work. the 94 uses the same jurid as your car you don’t need to modify the unit at all