Rear Engine/Transmission Mount Thumping
 

Hello, this is an issue on my '96 XJ12 but I've posted it in the X300 section due to the low traffic of the X305 forum.

I'm getting a thumping under the center of the car over bumps and irregularities in the road which I believe is from the rear engine/transmission mount.

The problem is I'm not really sure what a proper, healthy mount looks like.


Attached is what I'm seeing under the car.

And this video shows the kind of play I'm getting when I bounce the transmission with my hand:


It appears I'm completely missing the "Bush", Part MMC7553AA.

https://cimg5.ibsrv.net/gimg/www.jag...2f10b424dc.jpg

If so, would installation be as simple as removing the bolt from the bottom of that black "retention washer", slipping the foam insulator up the "damper peg", and bolting the washer back on, or does the whole mount need to be disassembled? If so, what precautions need to be taken?

IIRC, when I looked into trying to remove the bolt that holds the washer on in the past, the entire "damper peg" wanted to unscrew. Any thoughts?

Thanks,
Nick

Your entire mount will be tired. Replace the following: 1 spring MNA 7560AB, 1 Seat-Spring CCC 3764, 1 Bushing MMC7553AA. That's what came in the last set I ordered. Note: I don't remember it only needing 1 Seat Spring 3764 which is a rubber mount that slips over the end of the spring like a washer with sides. Check when you order to see if you need 2 of these as I thought it needed 2 but I'm old and my last set only came with one. Raise up tranny a little and support the weight of tranny/engine while changing out. It's a pretty straight forward repair, bout 3 beers... 1 before, 1 during, 1 after. Not much traffic for sure on the X305 forum they should merge it with the X300.

Thanks!

Parts come in at about $75, not too bad at all. I see both spring seats in the diagram, one on top and one on the bottom. JaguarClassicParts.com is only showing the required quantity as 1, but I'll check with my local parts department guy to see what he says.

So support the weight of the transmission, and it looks like four nuts come off then the whole mount drops down. Does the bolt at the very bottom (that I mentioned was so tight it was unscrewing the damper peg) need to come off separately, Or should I be able to let it just unscrew the damper peg?

Thanks,
Nick

Check out the following thread:

https://www.jaguarforums.com/forum/x...-mount-132540/

.

I had a knocking from this mounting too, and resolved to replace the foam bushing, springs etc. My ever helpful main dealer parts guy talked me out of the springs on the basis they had never sold any, and I just replaced the foam bushing. Knocking disappeared, and I am assured the considerable amount of travel in the mounting is "normal".
It isn't a big or difficult job, so might be worth giving it a try with just the foam bush, and only replace the springs if you still have a problem?

The tranny mount assembly is 20 years old and less than $100.00 new. Just replace everything as certainly the rubber seats for the spring are long gone along with the bushing. When I stand my old springs next to the new ones there has always been a difference in height as the old are tired.

I just replaced the foam bushing and that did the trick for me.

I used a transmission jack to support the transmission while removing the mount. First unbolt the four mounting screws to the vehicle, this will release some of the spring tension. Than undo the center bolt, that I believe is a T50 torx. The mount is heavy, so be ready when you have it loosened. To reassemble, I cheat and use a floor jack to put the mount in place and compress the springs. Those springs are strong.

So, this got me thinking. I did the front shocks this year and the rears a couple of years ago along with the rear shock mounts, and a still have a banging similar to both of those when they are bad. Most of it went away after doing the fronts. I didn't know about the transmission mount and it looks like there are two on the 4.0 XJ6L? Could this be the source of what I thought was suspension noise?

Difficult to be sure , but the video earlier in the thread might be helpful, plus you can feel the knocking with your elbow on the central armrest.
Im fairly sure your car only has one of these mounts.

I have a question--do you hear a clunk when giving the car gas in reverse?