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There is a knocking noise coming from the rear of my car which has persisted for some time. Yesterday I heard a clanging of metal coming from the back. Looks like some bushings desperately need replacing on the back of the differential area and maybe the rear sway bars?
I do not think its the rear swaybar, way too thick to be it. It does look like the differential strut but are you sure its actually the strut thats causing the knock? try to get a prybar down there see if it has alot of play.
Last edited by FrozenApple; 02-23-2015 at 11:56 PM.
There is a knocking noise coming from the rear of my car which has persisted for some time. Yesterday I heard a clanging of metal coming from the back. Looks like some bushings desperately need replacing on the back of the differential area and maybe the rear sway bars?
Hi TopHatChef,
FrozenApple is correct that the part in your photos is one of two "bushed differential struts," or "dogbones," Part 13 in this diagram:
The bushes in the differential struts are pretty robust and are not a common failure point, but it would be worth checking them with a prybar as FrozenApple suggests.
A common source of a knocking sound in the rear end is failure of the rear shock absorber top bushings, Parts 13 and 14 in this diagram:
If the knocking sound seems to come from behind the rear seat toward one side of the car, the shock bushings on that side are the prime suspect. Unfortunately, to inspect the bushes, you have to drop the shock/spring assembly (not that difficult), compress the spring, remove the shock top nut, the upper washer and bushing (Parts 15 & 14) and the upper mount (Part 6) so you can inspect the lower top bushing (Part 13). If the symptoms prompt you to go this far, you should be prepared to replace all the bushings, since they all deteriorate with age (Parts 5, 13, 14 & 17).
I recently replaced the rear shocks and all the bushings, so they aren't the culprit.
Let's put it this way: The car is 18 years old and for once I have a little extra money I can spend on it in addition to fixing the problem. So, what bushings are in the rear that typically go bad after 18 years or so? I read a little that the A frame bushings go, but I am also concerned about the two lowest bolts/bushings in the first photo (second photo is farther away and clearer). It looks as though those two are nearly gone.
I recently replaced the rear shocks and all the bushings, so they aren't the culprit.
Good...assuming the knocking sound didn't start after the rear shocks were replaced...
Another possibility is that an exhaust system hanger has deteriorated or broken and the exhaust is knocking against the suspension or body somewhere.
So, what bushings are in the rear that typically go bad after 18 years or so?
Short answer, all of them.
I read a little that the A frame bushings go, but I am also concerned about the two lowest bolts/bushings in the first photo (second photo is farther away and clearer). It looks as though those two are nearly gone.
Those bushings are in the wishbone tie, Part 6 in the first diagram in my previous post. Unfortunately Jaguar doesn't list the bushings as separately available parts, and JDHT lists the wishbone tie as NLA:
The bushings in the front differential pendulum also perish, Part 15 in that previously-referenced diagram, as well as the big subframe bushes you mentioned, Part 14 in the diagram below:
All of those bushings are worth replacing, and if you decide to proceed, you might consult with plums because he's done a lot of X300 rear end work and can tell you the upgrades you should consider, such as the X308 XJR subframe bushes and the X308 monostrut that replaced the dual dogbone differential strut setup on the XJ40/X300. Also, while you're at it, consider replacing the rear wheel bearings and differential output shaft bearings, and check your driveshaft center bearing and flexible coupling.
Below are links to photos showing the rear suspension rebuild on our '93 XJ40, which is very similar to the X300:
All of those bushings are worth replacing, and if you decide to proceed, you might consult with plums because he's done a lot of X300 rear end work and can tell you the upgrades you should consider, such as the X308 XJR subframe bushes and the X308 monostrut that replaced the dual dogbone differential strut setup on the XJ40/X300.
More like a lot of information collation and regurgitation
Look at the top of the last picture. The dogbone to body mounting point seems bent at the
rearmost ear. That might be camera angle, but it also does not appear perpendicular to
the through bolt.
I'm mostly confident that it's not a bent dog bone and just the angle of the camera, but I'll take a better look at it when I have the wheel off again. I guess I'll start with the A frame bushings since those are one of the more likely causes for the noise, then I'll just work my way around the rear and the front of the car. The front end could probably use a rebuild or a through replacement of some parts.
Ref the bushings in the wishbone tie, you can use the bushings for the pendulum which is listed as 17 in the diagram, so no need to buy the whole assembly.
I think it was listed in the XJ40 parts diagram, but there are many superseded parts numbers and it was difficult to identify when I checked once.
I've got a rebuild of my X300 4.0 Sport rear end coming upand would like to clarify a few things before ordering the parts.
Bushing part numbers are listed for the upper and lowerpendulum but nothing is listed for the rear tie/brace.
In the post above Japthug has mentioned that the pendulum bushes fit the rear tie.
It would seem logical that the lower pendulum bush would fit the rear tie for the control arm to tie connection. Does the upper pendulumbush also fit the rear tie for the tie to diff connection? Can anyone offer further clarification/confirmation on all the bushes in the rear tie and if they are interchangeable with the pendulum bushes?
I'm planning to replace the two dog bone struts with a single monostrut from the X308. I've also read some owners upgrade their A frame bushes CCC6875 to the X300 XJR / X308 spec. Is there any complicating factors in the fitment of the upgraded A frame bush?
Actually, inner bushings of wishbone tie, which fix the diff stud bolts, are not necessary, for later XK8 has the same wishbone tie without inner bushings.
As you know there are 4 spacers in front and back of the wishbone tie, that fix the diff stud firmly, so as a result the inner bushings don't work very much.
On X308s the inner bushings and the spacers are eliminated and the diff is mounted rigidly.
above: normal X300 wishbone tie<br/>below: early XK8 wishbone tie, note the inner hole without bushings
X308 sport wishbone tie, note the inner hole without bushings/spacers
Thanks Japthug. So it could be an advantage to source an X308 sport wishbone tie and do away with the inner bush altogether. Failing that are you saying there is likely to be minimal wear anyway on my existing inner tie bush and just re-use it? Do you know if it is interchangeable with the upper pendulum bush if I found it did need replacing?
And a couple more questions if you don't mind:
The lower pendulum bush and the outer tie bush are definitely identical?
Is there any problem fitting the XJR/X308 A frame bush? Is it just a direct fit to a standard X300 Sport?
Is the diameter of the bushed inner holes of the X300
the same diameter as the unbushed inner holes of the X308?
I have a X300 diff to put into a X308, and I need to keep
the X308 version because of the provision for the existing
anti-sway bar.
Hi.
Actually the inner hole diameter of the wishbone tie is different between X300 and X308.
So you can't fit the X308 wishbone tie onto X300 diff straightforward. The dia of the X308's inner hole is smaller than X300's, which means the diff stud bolts go into the hole is narrower on X308.
4 in the diagram above is the diff mount stud. The number for the X300's is CAC8228, while the X308's is NNC5715AA. These go into the inner hole. CAC8228 is thicker than NNC5715AA. So if you want to put on X308 wishbone tie onto X300 diff, you have to change these studs as well. But NNC5715AA is unbelievably expensive(£44.58 each @ jaguarclassicparts.com!).
Fortunately you already have the original X308 diff, so you can transplant the studs onto the X300 diff.
Thanks Japthug. So it could be an advantage to source an X308 sport wishbone tie and do away with the inner bush altogether. Failing that are you saying there is likely to be minimal wear anyway on my existing inner tie bush and just re-use it? Do you know if it is interchangeable with the upper pendulum bush if I found it did need replacing?
As stated above, you have to change the diff studs if you want to put on the X308 wishbone tie onto X300. All the X308 wishbone tie doesn't have the inner bushing, it's not because the wishbone tie is from X308 sport.
Here is a image I draw. As you can see, yes, the inner bushings are there but actually there is no play and the bolts are totally fixed rigidly by the spacer. When you get rid of the bushings it's all the same.
So don't worry about the inner bushings. Leave them as are.
Originally Posted by marke
And a couple more questions if you don't mind:
The lower pendulum bush and the outer tie bush are definitely identical?
Yes. They are the same.
Originally Posted by marke
Is there any problem fitting the XJR/X308 A frame bush? Is it just a direct fit to a standard X300 Sport?
BTW, I've been meaning to PM you. Did you not say at
one point you sell poly bushes? If so, which ones are
available?
Not at all, hope this info helps
Ref the poly bushes, I only provide with the shock upper mounts.
But I can have them make bushes at desired hardness as long as it is in a simple shape.
I always ask superior Japanese polyurethane maker to make bushes.
I don't recommend using poly bushes on pivot part though.
How much for all the bushings front and rear in poly? Fairly stiff versions. I dont mind the "stiffer" ride, Ive had cars with poly bushings before and really couldnt tell the difference in ride quality but did in handling.
Further to previous post I have done the X308 rear monobrace and wishbone tie with previously not stock rear anti roll bar . Great conversion and makes the rear end of the car so much tighter
Not a job to do without being on proper ramps . Also not a job for feint hearted . Tip of the day thouroughly clean all rust off pendulum bolts before replacing and loads of grease
02-23-2015, 11:17 PM
Some bushings need replacing, but what are they?
