We're expecting our second little future Jag driver soon, so I’ve been contemplating maybe finding something a little more practical to use for the daily grind rather than my X300, but I think I may have just been pushed into it…

It's been making a high pitched whine from the rear end for a while (a year at least), but my local 'specialists' couldn't work out what it was – they said the diff itself sounded pretty quiet. The pitch of the noise is dependent on road speed and independent on whether you're accelerating or decelerating etc.

The problem is that it has just started also making a much more nasty sounding noise, purely on the overrun. Not particularly surprising, but a bit annoying none the less!

So I figure it must be new diff time, but can anyone shed any light on what’s likely to be causing each noise? Just out of morbid curiosity really…

My concern is that due to the ridiculously low value of X300s in this country (and the not particularly desirable nature of mine!), it’s not worth paying someone to do the job if I’m then considering selling the car anyway. Hope I find time to do the job soon, or the poor car may end up going to the big carpark in the sky! L

 

I'll be interested to hear what the advice is as changing a diff on a Land Rover say is a 60 minute job on your back in a muddy field if you have the tools to hand. I assume in principle the process must be much the same.

I shall sit back and watch with interest.

 

Hi Ziggy,

My first suspicion based on your description of this noise would be a diff output shaft bearing. Often, but not always, by the time the bearing starts making noise, the oil seal has begun to fail and you'll see some dampness on that side of the diff, but your mechanic wouldn't have missed a leak. However, unless he used a stethoscope to check both diff output bearings and the pinion bearings, he may not have been able to detect the noise of a bad output shaft bearing by just listening from near the diff.

Wheel bearings are another possibility, but in my experience they tend to make a lower-pitched noise that changes when cornering, though not always, so I'd have both rear wheel bearings checked carefully.

Quote:

The problem is that it has just started also making a much more nasty sounding noise, purely on the overrun. Not particularly surprising, but a bit annoying none the less!

Diff gear noise on overrun may indicate worn pinion shaft bearings, which reduces the bearing preload and may also change the gearmesh between the pinion gear and crown wheel. Replacing the pinion bearings is a diff-out operation. In the U.S., professionally-rebuilt diffs are available at not-unreasonable exchange prices, and I would assume the same is true in the U.K. With jackstands and a transmission jack, you can swap a diff in one day in your driveway (see links below to photos of the diff removal and rebuild processes).

Some differential gear noise is inevitable, and a common issue with Jag saloons is that when the two large rear subframe or A-frame rubber bushings perish, they allow the diff carrier subframe to contact the body, transmitting gear noise directly into the passenger compartment. A lot of owners have swapped out perfectly good differentials only to discover that the noise was due to perished subframe bushes (Part 14 in the diagram below).



Another common source of rear end noise is a failed driveshaft/propshaft center bearing, which can also be checked with a mechanic's stethoscope.

I hope you don't need a rebuilt diff, but depending on how much of the job you could do yourself, it might be more economically prudent than buying a different car about which you know little or nothing.

Below are links to more photos than you ever wanted to see! The photos are of our '93 XJ40, the rear end of which is essentially identical to your X300.

Diff Output shafts:
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

Diff removal & installation:
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

Diff rebuild:
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

Rear wheel bearings:
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

Driveshaft/Propshaft Center/Centre bearing:
Welcome to Jag-lovers - Members Photo Viewing Page

Cheers,

Don

 

Don, that looks like a brilliant job on the diff. Inspirational.

 

Brendan,

Thanks for the kind words! After I was finished, my conclusion was that if I ever need a diff rebuild again, I will seriously consider purchasing a professionally-rebuilt exchange unit. It really is a lot of work for someone like me who had never done it before. It requires learning a lot of new concepts and a lot of trial-and-error testing with various shim combinations, which means the carrier has to go in and come out several times before you get it right. By purchasing a professionally-rebuilt unit, if the diff is noisy you have someone else to blame!

Probably the most significant considerations are: how much time can you spend in research before you start, how long can you afford to be without your car, and are you willing to invest in some tools you may not currently own (e.g. an inch-pound torque wrench, dial indicator with magnetic base, torque multiplier, etc.)?

If you're just going to swap in a rebuilt diff, the only tool many home mechanics may need to buy or rent is a transmission jack.

Cheers,

Don

 

Don,

An excellent job.

Now I've seen how it's done, I'll know never to even consider it for myself!

Graham

 

Due to the rather more complex nature of the Jag IRS setup, it'll be a slightly bigger job! Probably not technically any more difficult though...

 

Too right it is a bigger job! I think I'd feel intimidated by the job but if it was a choice between scrap or wrestle, I think I'd roll up my sleeves and wrestle. I imagine that getting the rear end good and high is helpful.

The joy of working on the giant Tonka Toys that Land Rovers are

You don't reveal where you are located in the UK but if it was local I'd bring some sandwiches and a chair and watch with great interest

 

Don,
Great stuff, thanks!

I'm perfectly capable of doing the work, but with a young family, a house with 101 (& that's a rolling total) jobs needing doing, a boat that I'd rather be racing than doing anything on cars or houses... the issue is finding the time!

I get your point about being better off with the car I know too, but it really doesn't fit my daily needs that well anymore, despite being a nice old thing to commute in! Like I said, I was contemplating retiring it to weekend use anyway.

I suspect the way forward will be to get it up on a ramp (stands at a push) and have a better listen to confirm what I think I already know. Then pull the diff and find a replacement... This will all be a rather more leisurely undertaking than when I've had similar jobs to do on a car I needed for work on Monday morning!

 

Hampshire, so possibly a bit far to come just to sit and laugh...

I've no idea how many times I've swapped diffs on my E30 - I would have probably enjoyed that job more if I knew how easy I had it!

 

So here's a good one: it's stopped.

I was on the way to a friend's garage to get it up on a lift and have a listen. At this point I'd probably done ~50 miles since it started making the noise; avoiding using it and certainly taking it very easy on the two drives I couldn't avoid. I was slowing down at the approach to a junction, and there was a 'pop' noise from the rear end, followed by peace and quiet! It's back to sounding exactly the same as it always has.

Up on the lift there was nothing obviously wrong - no excess play in the propshaft bearings, UJs, anything else I could think of...!

Since then (following a bit of paint while it was at the shop anyway!), I've driven another ~50 miles with no change. Obviously I suspect it hasn't really fixed itself(!), but I'm at a loss as to how to explain it. A stone caught in the brakes wouldn't only make a noise on the overrun; likewise a disintegrated handbrake shoe; a bearing surely couldn't go quiet having been that noisy (it was a proper metal-on-metal sound)...

Any ideas?!

 

So now my X300 is shinier than ever (well it was never that shiny before, but it's less crusty anyway!), and it's really good to be back behind the wheel after the 'lovely' gold Skoda (derv, of course) I borrowed for the last couple of weeks... I think I need to make space to keep it alongside a new daily driver

 

Well, that is interesting and good news.... although I agree it is suspect when something clearly amiss just clears up magically.

I could stay gone, but time will tell.

But on the bright side, sounds like you have a new lease on life for the X300 and one less thing to worry about at the moment

.

 

I hate it - I'm constantly listening out for it to come back! Ive done a couple of hundred miles since though, and no change.

Still looking for something newer to rack the miles up in...