Hello, I haven't come on here to ask about a project in a while! I am experiencing a squeak over small bumps that "might" be coming from the rear. It's not loud and not even that annoying but it's there. The front suspension is all new. The other red flag is that the driver side rear is about 1/2 to 3/4 inch lower than the passenger side rear, which itself also is lower than the 14.6" specification (measured from center of hub to apex of fender). I have found numerous posts explaining how to do the job so I think I'm good there.

While my normal inclination would be to just do a complete rear suspension refurbish like I did on the front, sadly my company recently closed both the the locations I was the manager of so I've been laid off (not that uncommon right now, no sympathy necessary). This also means after many years of company cars I am now temporarily using the XJR as a daily driver, although other than The Home Depot and the occasional job interview I have nowhere much to go. So, spending lots of money on new shocks feels irresponsible. With 107k miles I'm thinking the shocks themselves are probably fine (adaptive by the way). I want to pull it apart to see what ACTUALLY needs replacing, but there's really no way to see without full disassembly; in which case I may as well have the parts on hand an put it back together repaired. Down time is a problem now since my company daily driver is gone.

There is another complicating factor. According to the tire shop my two front wheels are "egg shaped" causing some vibration above 65mph (only when they are on the front, never noticed a problem when they were on the back). I'm guessing I'll have to budget for 2 new Asteroid wheels at some point too!! I have to make a 10 hour round trip drive this weekend to help my mother move. I HATE to rent a car but I'm unsure about a drive that long if the suspension may be suspect (and 2 of the wheels).

Any reflex advice from some of my old friends on here about how to proceed?

 

You can probably have a local wheel repair company evaluate your wheels if they aren’t too terribly bad.

The rear suspension sag on the left side could be from a weak/leaking shock. If they appear ok when you have them out, you could swap the shocks side to side and see if the sag changes. There are many other things that can cause that sag also, but that’s one of them. I would highly recommend getting oem Jaguar rear upper shock bushings as the aftermarket large donuts are just garbage. Instead of the oem foam (not that it’s great), the aftermarket ones are made from plastic and they squish like a marshmallow when under weight.

 

the problem is that the shock bushings actually cost more than a whole new shock once you add it up. cheapest way to get all the bushings is to buy the $50 pair of sensens on ebay and press out the bottoms. if you need more lower bushings use mb part 201 352 00 27.

 

A couple of observations:
The lower shock bushings certainly appear to be in need of replacement (see photo). It also seems if I jack up each control arm with the car off the ground the spring on the drivers side rear compresses more and doesn't lift the car until it's almost up to the bump stop. The coils are clearly closer together than the coils on the other side when I perform the same test. I cannot discern if the shock is moving though, in fact neither side makes any noises or clicks. It raises smooth and quiet.

The car has CATS suspension and the rear shocks are green. From what I can see of them they look like MNC3540EB, which is the adaptive sport shock. The cheapest I see them anywhere is $339 each! I'm guessing they come with ALL of the necessary components including the isolators (numbers 21 and 22 in diagram below). All I would have to order are the shocks and the donuts for the upper part of the springs (number 5 in the diagram below), correct?

 

yes new shocks come with all bushings washers etc except for the coil seats which are 30 something each

 

Another thing. The mechanic said my front wheels were not round; egg shaped to use his term. I did the following test and they look good to me. Is this test not valid?

 

Did the mechanic conclude that the "wheels are egg shaped" by, when the wheels are rotated, looking at the tyre play or at the rim play?

 

Rockauto is about 99% of the time the lowest prices I can find.

This oem Jaguar coil spring isolator would be just a few dollars more than aftermarket. This is on eBay.

It is possible that the technician may have thought your wheels were out of round when in fact your tires could be out of round?? If you have the vehicle up in the air and you grab the tire and spin it as hard as you can and there’s up and down movement from the tire, it could be a bent rim, excessive “road force” variation of the tire or a belt separating in the tire. Road force of a tire can be measured on a road force balancer machine which not a lot of regular shops have. You could call tire shops around and ask if they have one of those machines.

 

M. Stojanovic -- I don't honestly know how they determined the tire wasn't round. I went to that shop because they got great reviews for their road force balancing and I was feeling a little vibration, sometimes, in the front tires at around 65 MPH. They said when they put it on the road force machine it was already almost perfect. They said the dynamic balancing was a little off so they corrected that and said maybe that'll make the vibration less noticeable until I could source new wheels. I found the test I put the video of above online somewhere. It seems simplistic but it makes sense, right? They only charged me $17 for the dynamic balance and didn't try to sell me wheels.

Addicted2boost -- Thanks for looking those up for me! I did find the ones on Rockauto yesterday after I made that post. It seems when I bought the adaptive shocks for the front a few years ago Rockauto didn't sell them, maybe that's why they weren't the first place I checked. I put them in a basket and found the OEM donuts at Terrysjag.com for $40. I'm not sure if I feel comfortable spending the money right now but, we'll see. The car had 2 Michelins in good condition and 2 that had low tread when I bought it about 4 years ago. I immediately bought 2 new matching Michelins. Now, the 2 that were good then are pretty worn now and they happen to be the wheels where the vibration came from. I ordered 2 new Michelins last night (clearance pricing was great!). The other 2 Michelins that I bought 4 years ago still look practically new.

 

Could it be your tyres are simply cupped? ( see https://www.utires.com/articles/cupp...revention-faq/ )

It happens, and in particular on cars with worn suspension. There is nothing you can do about it, the tim/tyre will still balance perfectly on the machine, but it doesn’t solve the problem of cupping. It usually manifest itself as a humming sound, similar to a bearing going bad. Except with cupping the noise is present continuous and does not change when cornering.

Some cars and some specific tyres are more prone to cupping. E.g. my wife’s little Ford Fiesta is very prone to it. It is one of the few cars where I still rotate tyres, just to prevent cupping. Once a tyre is cupped there is nothing that can be done about it. Live with it, or replace it. But it is important to find the root cause, which to all intents and purpose appears to be some issues with the suspension.

Good luck

Jeroen

 

Thanks Jeroen, that's an interesting link.

I would "like" to think that an experienced tire shop like the one I went to would know the difference between a bent rim and a cupped tire, but I have no history with this shop or those mechanics so who knows? The tires on those rims are in fact older and worn, and were just recently rotated to the front. I rotated them back to the rear a few days ago and all the vibration issues (mild as they were) are now gone. I had 2 brand new tires delivered yesterday so at some point in the next couple weeks I'll schedule to have them put on the car. I'll go to a different shop and ask them to mount and road force balance them onto the 2 wheels in question and see if they tell me the same diagnosis.

The cupping theory could be possible since the rear shocks are original (107k miles) and these tires spent most of their time on the rear. But, they made NO noise at all and they don't look cupped based on the explanation in the link you provided. I already ordered the upper spring donuts and am hoping be able to afford the new shocks by the end of the month. The car drives and handles nice but seems to ride a little too low in the rear and has a small squeak/rattle over bumps. I think the shocks are still good but given that they have to come out to replace all the isolating components I would really prefer to just replace the shocks and be done with it for another 100k miles.

 

Just a little update

I received the spring isolators/donuts and I'm sure it means nothing but they don't look alike. They are exactly the same dimensions of course and both seem to be solid but one has dark coloring with black charred looking coloring on part of it. I presume this is normal in production of these types of items and it's not important? Right? (see picture).

The new BILSTEIN electronic shocks were scheduled to arrive yesterday but apparently Fedex is having problems and have moved it to "pending" for now. I have no idea when they will actually arrive but I guess I'm in no huge rush.

And of course, the new tires are ready and waiting....

 

The shocks finally arrived. I think I’ll start working on it after church today. Anybody have any feedback on whether the spring isolators being different colors makes any difference at all?

 

If I were in that position, I think I would go ahead and install them even though you might already be done with it by the time this is posted. But, this I can assure you... I would install a pair of the dark brown oem ones vs any new aftermarket ones. My guess is that the dark brown one has some age to it?? I really don’t know but I’ve seen them before with no issues.

 

Hey, thanks for that. As long as I have your attention....

The directions I'm following say to put "quality" grease on the spring isolator. (see picture from directions below). The one that came out does not seem to have been greased or at least it didn't discolor the isolator. I have axle grease and multi-purpose silicone grease (in my grease gun, that I used to grease the axle u-joints).

Should I put grease on the isoloators and if so, which grease would be best?

Thanks,
PS- I haven't done any significant work on my car in months...this is kind of fun!

 

I never heard of putting grease on the isolators before. Maybe Bob could chime in on that one?

 

Well, all is installed and the biggest noticeable difference is handling. It feels much better in corners now. Also, it would occasionally tramline a little; hasn't done that yet (only 20 mile test drive). Rear height is more even side-to-side now and the steering feels "sportier", The ride is better also but not dramatically.

The only surprise during the installation (that's not mentioned in either of the tutorials I read) was the A-frame bushings not lining up just right. With all bolts installed and torqued the last step was to bolt the bushing to the frame but it was an inch too low! I used floor jacks to ease them up into position. It ultimately went back together fine so I'm not sure what to think....

Thanks for the feedback

 

Those 2 A frame bolts never line up together. What you experienced was normal. Drive and enjoy. 🙂

 

I have to make one more comment about this project. I spent 4 hours today running errands with my daughter and her best friend and the difference in the way my XJR drives is remarkable. I had no idea new rear shocks would make such a profound difference in the way it handles. If your rear shocks are old and you are on the fence about replacing them... go for it. The “fun factor” on my XJR jumped a few notches!