I'm hoping some of you Jaguar geniuses can help me with this problem I've been having for the past year. This problem has turned into harsh grinding noises and rumbling which would vibrate the whole car while driving. The problem mostly happens if I come to a stop or I should say a hard stop when I go to accelerate the car vibrates and rumbles but if I take my foot off the accelerator and then accelerate again the car would accelerate smoothly. It started mostly as an intermittent problem during hard braking. Now it's turned into and every time occurrence. I have no clue as to where to even start to look. The transmission mount fluid and filter changed a little over a year ago and the fluid is properly filled

 

Forgot to mention I have a 1989 X JS convertible with automatic transmission and Marelli ignition

 

Here is my "diagnosis" ie guess!

The gearbox mounting had had it and/or the bolted-up-to-the-tunnel two-part metal 'shelf' that supports the GB tail has become mis-aligned; thus allowing the tail of the GB and the propshaft at the gearbox end to grind on the aforesaid shelf.

Do not ask how I know this can happen... So I suggest renew the gearbox mounting and also the engine mounts to the front subframe, hours of fun...

Greg

 

i have a similar problem , and took her to a gearbox guru here in the Uk

he diagnosed the first and second gear bearing ( torrington bearings ) and also the internal braking band as faulty

i elected to buy a used GM400 ( TH400 or turbo 400 )box ( which is what you should have to ) and a full rebuild kit from the US , about $200 worth and rebuilt it myself

just got to fit it now

my suggestion is to take it to a transmission shop , and ask for someone to test drive and give their opinion , and pay him for his time

but dont commit to anything right there and then with regard to fixing it without some more research

good luck

BB

 

I had a similar grinding noise I thought was coming from the transmition when accelerating hard and very hard braking. I discovered that the driver’s side motor mount was missing the single nut that keeps the two halves together and under heavy toque the motor would twist and the fan blade would hit the fan shroud.
I only discovered this when, while stationary, I put the car in drive and foot on brake and torqued it up while a friend watched and listened under the hood………fan hits shroud. Also fan tips have scuff marks on them.
Just relaying my experience, as I was about to pull the tranny, and it looked like a big job.
Good luck!

 

the above is a very good way to diagnose worn motor mounts , and is useful to remember as i have seen this before


in my case i have all electric cooling, so the engine moving doesn't move the fan


BB

 

The tranny mount was replaced less than a year ago. Which is when the problem first started happening. I'm thinking that maybe the transmission moved out of alignment when this was done? How would I go about re-aligning it? I'm hoping for a smile fix before I have to start digging deeper into a tranny repair or replacement. What troubles me is why would it correct itself ( 95% of the time) when I put the car in neutral at a stop light before putting it back in Drive? Also there has been vibrations throughout the car while quickly accelerating up to speed.

Thank you so far for your input.

 

I wonder if the transmission mounting was incorrectly reassembled, causing an alignment problem?

The problem you're experiencing sounds fairly severe....enough so that a simple visual inspection might reveal the root cause.

Jaguar has had a decades long love affair with overly complex gearbox mouting schemes:

Gearbox Mounting-5.3 Litre - Parts For XJS from (V)139052 to (V)179736 | Jaguar Classic Parts UK

The mounting on a Ser III XJ6 is even more convoluted and I managed to assemble it incorrectly, resulting in the transmission being incorrectly positioned....and quite obviously so. When I was done I took one look and said "Hmmmm. That ain't right" before I even lowered the car to the ground!

Just thinking out loud.

Cheers
DD

 

I am pretty sure that this is the reason. The trans mounting is a two piece affair, only ONE of which is shown in the diagram (piece 9 the buffer plate is a safety device of some sort and NOT part of the mounting, although it has to be removed to do what I outline below). As a whole, the mounting provides a "shelf" across the tunnel bottom on which the tranny sits supported by a spring with a spigot down the middle of the spring to stop the tranny jumping off the "shelf". The bottom of the spigot pokes though the mounting shelf and is bolted up.

The two piece mounting plates look like this when out of the car (just happened to see this pic on ebay):
JAGUAR XJS GEARBOX MOUNTING | eBay

The trans has to be put in as follows:

• Support trans in place and bolt up the propshaft to it.
• bolt in the bit with the half round shaped upright
• mount the spring and place its damping rubbers each end
• insert the OE rubber cotton reel bush in the holes in the second piece
• bolt in the second piece

Now, if the trans it a little out of alignment to start with, and all these stages are gone though, the propshaft WILL catch on the half moon upright piece under certain conditions and/or the tunnel (eg acceleration, hard stop). I think this is what is happening to you, and all your symptoms are explained by it, as the tranny realighns a bit once in neutral, etc etc.

Also, the rubber cotton reel is crucial, I found. I fitted a more solid aftermarket one, and this also contributed to the problem. This is because the cotton reel actually damps the spring movement, and when the OE one is fitted and the spigot nut that goes through the mounting "shelf" is done up tight, the cotton reel is compressed a bit, and the tranny thus pulled lower, and the propshaft away from the tunnel. The aftermarket reel is far far harder stuff and does not compress at all when bolted up tight, to the extent that on my car the nut would not fully go home on the spigot.

So I suggest that you:

• support the tranny from below
• undo the spigot nut
• separately support, loosen carefully and remove the mounting piece with the cotton reel in it
• this then allows you to see the first mounting piece with the half moon upright. Loosen this one's bolts and place it carefully as equally as possible round the propshaft. The mounting holes are slotted for this purpose, ALSO you may find that not all the mounting bolts are there! If so they must be replaced or otherwise the mounting will catch the propshaft. Note that there should be bolts on the top if each side of the half moon shaped piece that go sideways into the tunnel. There is a good chance that these have NOT been put in!
• reinstall the spring with an OE cotton reel if yours was not such
• insert the spring onto the spigot, compress it up a bit so you can start the bolts, and do up the bolts enough to hold it but do not tighten them.
• remove the tranny support and give the tranny a hard up and down movement against the spring.
• then place the second piece as centrally on the spigot as possible by levering it or tapping it, then do up the bolts tight.

This cured my similar problem. Also there is a special little washer (28 in Doug's diagram posting) and a tubular spacer (27) that must be placed, little washer first, then tubular spacer, on the spigot before the cotton reel in its mounting plate is pushed into place on the spigot. Finally there is a BIG special washer (21) to be placed against the cotton reel dished side DOWN, before the tongue shaped piece (18) and finally the nut on the spigot! The buffer plate (part 9) can be dispensed with according to several owners.

Some pics, first the spigot on the tranny (propshaft disconnected in this photo)


Second pic: the two pieces of "shelf in position, you can see the propshaft there too, and that there is not a huge clearance. Note that there are tubular spacers on the bolts in the pic RHS between the first and second piece. These bolts hold the rear of the second piece and the bolts go though into the first piece.


This is a bit long, but you did ask !!


Greg

 

Thank you, I'm gonna attempt it later this week. I'll let you know what happens.

 

Good luck. Also note that one of my instructions may be badly worded "Finally there is a BIG special washer (21) to be placed against the cotton reel dished side DOWN,"

By this I mean that the smaller central part of the washer should be UPWARDS so it locates the tubular spacer (number 27). In other words if you imagine the special washer looks a little like a bowl, the dished bottom is downwards and the indent for the tubular spacer is upwards.

Greg

 

So i know this is an old thread but i wanted to say a BIG thank you to Greg for this post.

I have had a knocking/banging noise ever since replacing the trans mount after and engine and trans removal a few years back when starting what has now become a five year project.

After some time i worked out that the prop shaft bolts were just touching the "Half Moon Plate" but only under acceleration, lifting off stopped the knocking.
I thought this was a height issue and have tried taking apart and rebuilding the lower plate and associated items multiple times. Having to jack up the vehicle and remove/refit the trans mount is time consuming and frustrating work.

When i could not figure out why i could not get the height set so it would not knock i decided to go back to this forum and start looking again. This post was found after some time looking at the multiple information about this troublesome mount, the wonderful feeling when reading about the upper plate alignment and realising this was a probable problem was a huge relief.

Back to the car removed the lower plate and items once more with a giddy feeling of hope. Removing the upper plate showed exactly where the contact was being made and the witness marks were off to the right. Replacing the plate i moved it over towards the right along the elongated holes tightened it up replaced everything for the five or sixth time and lowered her to the ground.

A quick test drive up the road and even under full acceleration no noise :-).

Again HUGE thanks to Greg for this post showing that no matter how old a thread may be it could just be the one thing that helps others

 

I greatly appreciate this kind and generous thank-you. I am delighted that is was useful for you. Good luck with the car. Incidentally, I currently have a different sort of problem, which I am fairly sure is the torque converter in my gearbox going home. So soon there will be a fully illustrated how to remove the gearbox thread, should you ever need to do it. Once I have got the front suspension of Madame's fine Mondeo estate car back into the chassis, that is!