Is it possible that the road noise I hear in my '88 XJS is coming from a transmission mount that has flattened out due to age and is resting directly on the frame? The noise changes with speed, decreasing all the way down to zero when motion is stopped. I'm currently investigating wheel bearings but I noticed in the CarFax I got with my car that the transmission mount was replaced at 25K miles, The car currently has 92K miles on it. I haven't checked to see what I have for a mount yet. Any ideas?

 

Assun=ming a V12??

I think a proper look see at the mount and its alignment is step #1. If its been reassembled wrong, then its wrong, and noise and vibration will always be there.

The front Uni Joint clobbering the vertical section of the tin plate is also SOOOOOO common.

 

Thanks Grant. I'll have it up on 4 jack stands this weekend and will learn more about what's there. If it's anything like what was under the bonnet when I first opened it up, I'll be lying on my back staring in wonderment for a while. . Damn, I like this car !!!

 

. . . and the wonderment will turn to amazement once you retrieve all the small spanners, nuts, bolts etc that fell from above, but never reached the ground!!!

One small addition to Grant's . . . if tempted to disturb shaft for R&R trans mount and/or UJs, first mark all mating surfaces coz balance is critical. Unfortunately, this is one area where you are at mercy of previous owners or a clueless mechanic because incorrect assembly is surprising common.

Cheers,

Ken

 

Goodo,

Dont forget the loooooooong small plastic tube taped to your Left cheek, the other end in a LARGE bottle of JD, and then whilst admiring Britian's finest, you can "sip away" and eventually it will all be as clear as mud.

Ken is spot on with the marking of things, and take photos, LOTS of snaps, your memory is NOT that good, trust us all on that one.

This might help:

Jaguar TH400 transmission mount explained.doc

 

Further to Grant's link, this might help too:
https://www.jaguarforums.com/forum/x...itting-145478/

 

Thanks for the documentation advice. I'm not taking any chances about documenting what came apart on this car. With all it's complications I still love it. Maybe I'm some kind of self-sadist but I definitely enjoy the challenge of beating my head against the wall and still living through it.

 

Don't forget; if you don't scrape your knuckles, tear off the odd fingernail and bleed over it at least a little bit then it will never respect you.

 

Ah gosh . . . Sticky that last thought !!!

 

GUYS.

A V12, and in the XJS guise, is NOT complicated. Very simple really, just DIFFERENT.

It is we humans that make it complicated.

Hence the JD and the plastic tube.

 

Is that what you have Grant?
You can wheel yourself around under the 4 post lift at the same time.
Put it on your Christmas list.

 

Almost.

The JD is firmly glued to the concrete floor, near the shed wall, so I dont knock it A..e up and spill the Necta.

The Mechanics Creeper has 6 caster wheels, and a padded pillow.

Slides sweet under a Jag on 4 of my modified safety stands, and the tube is about 3mtrs long. That tube gets run over too often, and a new tube is needed, must find a better solution one day, but cannot rush these modifications though.

Of course this ALL in the past, since I went on the wagon, but the memories are crystal clear, well almost crystal clear.

 

Got to ask this, because so many people say so: why should the propshaft be balanced with the transmission and co? The shaft is balanced in itself. If ypu separate the ends (so take the splined end off) then ypu can get an imbalance.

otherwise: why don't the manuals state to rebalance the prop if replaced? Or if the transmission is replaced (happens), why isn't it said to rebalance it all then? Doesn't make sense. And it is a lot more awkward to balance a prop and co fitted to a car than it is to do it outside. You don't balance wheels on the car, but on an external machine, right?

 

Makes sense but I’m sure others will know more

 

Agreed; makes no sense. Never heard of it being done, personally

There IS such as thing as on-the-car wheel balancing....but not commonly done

Cheers
DD

 

The prop-balancing statement I would class as an urban myth.

I've seen on car wheel balancing before, but that is only ever used for super expensive cars with super high speeds, where a nornal tolerance of 0.05g would end up causing massive problems.