Craig Sawyers wrote:>
Also, I have a shudder from transmission when moving
off and also on upchanges. Not too violent, but a
full power take off provides a lot of vibration.
I have been told, prop shaft adjustment (done - problem
still there). Transmission mount - is this a big job
While it may seem to be the transmission or prop shaft the
engine could
be missing under load.
Well, my XJ12 (that I completely rebuilt) used to do this before the
rebuild. I have replaced just about everything on the car that wears,
including all UJs, the centre bearing and the little rubber donut on the
rear tranny mount (remember, I have a GM400, not a BW box, but the
arrangement is similar).
I still have that (exactly the same!) shudder on full power take off
(but not between gears).
Now the only thing I haven’t done is replace the rear mount spring. It
looked in good condition, and measured the correct length (from Kirby’s
XJ-S bible). However, I bought a new one, so on an idle day sometime I
can replace it - and Jag have both changed the part number, the gauge of
the wire and the number of turns. It is also a different length. There
is no point giving the part number, since it will be different for the
4.2 car. But, the point is, there may be a similarly uprated part for
the 4.2 - so it is worth checking with the dealer.
Craig
Craig & All
Suggest to you as to Lyndon that the source of the “shudder” is
combustion related and your mounts et al are fine. Similar to your
replacement of bits a new trans mount was installed here plus a freshly
rebuilt trans, new motor, and continued having the same experience.
Light throttle = no shudder but any increased application especially
from rest and the vibration would be there. A particular intersection
from neighborhood to main road would produce, when entering from the
stop, not only the shudder but a flare up skipping 2nd as well no matter
how judicious the application of the pedal. This was always when cold
and just starting out.
Thinking transmission problems ( great, the thing is brand new ! ) spent
a month or so making sure the fluid was at the right level, pressure by
the book, moving the rear mount around, checking mounts, etc. In the
last week got to thinking that it was time for a plug check. Pulling the
plugs they appeared a bit bluish at the tips ( lean ). Changed plugs.
Remembered other listers comments regarding vibrations being caused by
crossfire between plug leads so with some wire guides from the local
parts store the leads were isolated from each other. Still bothers me
that the leads simply lay on the cam cover as they go from distributor
to the plugs. How come the XJ’s don’t have some of those spif wire
holders like the older XK engined cars ? Got things warmed up and
attached the VOM to the O2 and adjusted the AFM.
Result of new plugs, taking care in the routing of the wires, and
resetting the mix, is no stumble or vibration. No trans slip or flare
either. Pulls great from idle on up. So where it could have been sworn
the trans was the source of woe complete with visions of it grinding
itself into little pieces it is just fine thank you.
Excuse the use of BW here but thought it worthwhile for Lyndon who is
trying to find a competent Jaguar mechanic and Craig who still
experiences the vibes with his virtually new XJ-12. If your doing your
own work the hunt is measured in your own patience. Big difference if
your paying someone to go out and bag the cat for you.
Happy Trails,
Paul Spitzer
Put a wide board between the oil pan and a