Another chuffing noise
Discussion
Except this one doesn't "chuff", but it's chuffing annoying.
This one is like a whirring noise that starts at about 20mph and whirs according to road speed.
Knocking it out of gear so the engine is idle doesn't change the noise (except it gets slower again).
If I put my hand on the parcel shelf I can feel a related vibration, but equally I can feel it a bit through the steering wheel.
I have tried the following - replaced both front wheel bearings (they seemed fine anyway). Jacked up the rear of the car and then supported the hubs to stress the driveshafts. Then stuck it in 5th on fast idle (=30mph) and listened underneath. Couldn't really hear anything definite.
I have checked fluid levels in diff and gearbox - all OK.
The car went through the MoT with the noise and I got no advisories about noisy wheel bearings, besides the rears seem OK when rotated by hand.
Apart from the noise it drives fine, the noise doesn't vary around corners etc.
Any ideas?
I am thinking of rigging up a clip-on microphone so I can listen to various parts while driving.
This one is like a whirring noise that starts at about 20mph and whirs according to road speed.
Knocking it out of gear so the engine is idle doesn't change the noise (except it gets slower again).
If I put my hand on the parcel shelf I can feel a related vibration, but equally I can feel it a bit through the steering wheel.
I have tried the following - replaced both front wheel bearings (they seemed fine anyway). Jacked up the rear of the car and then supported the hubs to stress the driveshafts. Then stuck it in 5th on fast idle (=30mph) and listened underneath. Couldn't really hear anything definite.
I have checked fluid levels in diff and gearbox - all OK.
The car went through the MoT with the noise and I got no advisories about noisy wheel bearings, besides the rears seem OK when rotated by hand.
Apart from the noise it drives fine, the noise doesn't vary around corners etc.
Any ideas?
I am thinking of rigging up a clip-on microphone so I can listen to various parts while driving.
Bear in mind that the car went through the MoT with this noise so the bearings must be OK. Brakes and UJ's too.
Today I stuck in 25psi all round and the noise seemed to get less, so maybe it's tyres, I'll try reducing and see if it comes back stronger.
The odd think is that the tyres are well used and the noise has only just appeared, so I have been reluctant to blame them, but maybe it's the tyres, more investigation needed.
Today I stuck in 25psi all round and the noise seemed to get less, so maybe it's tyres, I'll try reducing and see if it comes back stronger.
The odd think is that the tyres are well used and the noise has only just appeared, so I have been reluctant to blame them, but maybe it's the tyres, more investigation needed.
Just changed the diff oil, which was a bit low, by about half a litre, and quite black+silver.
Also noticed the filler plug had some score marks on it, maybe due to being tightened into the hole too much.
As it's a tapered thread I bunged on 3 turns of PTFE take to make it seal with less screwing in.
Anyhow all back together and a test drive and the noise persists.....
Maybe a tyre/wheel swap next...
Also noticed the filler plug had some score marks on it, maybe due to being tightened into the hole too much.
As it's a tapered thread I bunged on 3 turns of PTFE take to make it seal with less screwing in.
Anyhow all back together and a test drive and the noise persists.....
Maybe a tyre/wheel swap next...
Well a recon one is around £1200 but maybe all they do is polish the outside....
I've done OK on s/h gearboxes, which are far more complicated.
Regarding your suggestion of the propshaft I've never had a problem putting them back in upside down. The prop was last disturbed when I changed the gearbox around 7-8? months ago. And this noise wasn't evident then.
I had the rear up on axle stands the other day (to stress the bearings just the same, wheels on) and got it up to indicated 50mph but the noise didn't really appear. So it may be from the front but I'm struggling to work out why.
I've done OK on s/h gearboxes, which are far more complicated.
Regarding your suggestion of the propshaft I've never had a problem putting them back in upside down. The prop was last disturbed when I changed the gearbox around 7-8? months ago. And this noise wasn't evident then.
I had the rear up on axle stands the other day (to stress the bearings just the same, wheels on) and got it up to indicated 50mph but the noise didn't really appear. So it may be from the front but I'm struggling to work out why.
Well the noise has slowly been getting worse, one extra piece of information is if I start zig-zagging along the road, the noise disappears on the zig to the left, but reappears straight on and/or zag to the right.
E.g. when exiting a roundabout, there's a temporary respite.
So I just jacked up the rear of the car again and also mainly jacked up the left rear so it was under compression, and running the rear wheels at about 40 mph the noise is evident, and seems to be coming from the diff (confirmed with jack handle on diff other end on ear).
So my money is on the left hand diff output bearing, and as the oil seal seems to be a bit weepy too, this is probably the area to attack.
Anyone know can it be replaced in situ or is it easier to drop the whole lot down to allow easy access - get brake caliper off etc?
E.g. when exiting a roundabout, there's a temporary respite.
So I just jacked up the rear of the car again and also mainly jacked up the left rear so it was under compression, and running the rear wheels at about 40 mph the noise is evident, and seems to be coming from the diff (confirmed with jack handle on diff other end on ear).
So my money is on the left hand diff output bearing, and as the oil seal seems to be a bit weepy too, this is probably the area to attack.
Anyone know can it be replaced in situ or is it easier to drop the whole lot down to allow easy access - get brake caliper off etc?
Well it turned out the top bracket has 4 bolts and the easiest was to get it off still attached.
I have stripped off the calipers, discs and side bearings and also had a look inside.
There isn't a definite "bad" side bearing, although the right hand one seems a bit stiffer to turn than the left one.
The side bearings are definitely leak-free.
The front bearing shows a bit or end float, and if I press on it while turning I get a noise from the diff internals, so I wonder if that's the problem, well it seems to be a problem anyway. As I recall the front bearing is the technically more difficult one to replace? It also leaks so the seal needs doing.
The crown wheel teeth look in good nick except for a small chip on the very corner of one, but it seems far away from where the pinion should engage so probably not an issue.
I have stripped off the calipers, discs and side bearings and also had a look inside.
There isn't a definite "bad" side bearing, although the right hand one seems a bit stiffer to turn than the left one.
The side bearings are definitely leak-free.
The front bearing shows a bit or end float, and if I press on it while turning I get a noise from the diff internals, so I wonder if that's the problem, well it seems to be a problem anyway. As I recall the front bearing is the technically more difficult one to replace? It also leaks so the seal needs doing.
The crown wheel teeth look in good nick except for a small chip on the very corner of one, but it seems far away from where the pinion should engage so probably not an issue.
Yeah LSD. Thanks for the pointer I found one about jag diffs a few months back too.
In my case the friction area doesn't need fiddling with that's all working OK. I think it's mainly the pinion bearing end float that needs sorting out, and front oil seal, and probably do the side bearings as these are only around £15 a pop.
I may take out the central workings so I can inspect the pinion drive gear.
In my case the friction area doesn't need fiddling with that's all working OK. I think it's mainly the pinion bearing end float that needs sorting out, and front oil seal, and probably do the side bearings as these are only around £15 a pop.
I may take out the central workings so I can inspect the pinion drive gear.
I just found this article:
http://bernardembden.com/xjs/diff/index.htm
which is excellent and may be my answer. Too bad I didn't realise the pinion end float was bad before dropping the diff.
I could have tried this a few days ago and given it a go and saved myself a big old job - hey ho you live and learn.
http://bernardembden.com/xjs/diff/index.htm
which is excellent and may be my answer. Too bad I didn't realise the pinion end float was bad before dropping the diff.
I could have tried this a few days ago and given it a go and saved myself a big old job - hey ho you live and learn.
More good reading material here:
http://dazecars.com/dazed/Diff.htm
e.g. the table here: http://dazecars.com/dazed/JaguarIRS2.html is very useful.
http://dazecars.com/dazed/Diff.htm
e.g. the table here: http://dazecars.com/dazed/JaguarIRS2.html is very useful.
This is a useful piece of advice if you're trying to diagnose things:
Bearing whine tends to be there from low speed all the way up and doesn't vary much as you ease on and off the pedal. Gear whine is at tooth contact frequency and is most prominent around 60-70mph (about 2000 Hertz). You can 'play' diff gear whine on the throttle and its sometimes more prominent on the overrun when the 'rear' sides of the teeth touch
Bearing whine tends to be there from low speed all the way up and doesn't vary much as you ease on and off the pedal. Gear whine is at tooth contact frequency and is most prominent around 60-70mph (about 2000 Hertz). You can 'play' diff gear whine on the throttle and its sometimes more prominent on the overrun when the 'rear' sides of the teeth touch
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