Gearbox mount - early V12 manual

[iRS]

Can anybody offer any advice on what the correct gearbox mounting is for the early V12 factory manuals please? When I took the engine out I found only disintegrated pieces of a rubber bush and its unclear to me what this should look like. I've looked at the parts diagram and one of the bushes listed is CAC3227, but this seems to be an error as it is the one for the autobox and doesn't seem to match with anything I've got. Both are pictured here:

This is what the rest of the assembly looks like:

and as removed:

[PaulGover]

I only know about the later auto V12s, but that mount looks just like the one fitted to mine, and to my 1981 XJ6, and the 1974 XJ6 before it (Jaguar work on the "if it ain't (drastically) broke, don't fix it" principle )

The orange bits of rubber appear to be the remains of a CAC3227. That's what usually happens to them In fact, there's more of yours left than I had last time I changed one! They dissolve in engine oil. When it started out it looked like an over-size cotton reel. (I note that SNG Barratt sell two versions, the Jaguar original in pink bath sponge, and a (cheaper) black rubber one. Might be worth calling them to see if the latter resists oil better.)

The design is that the cotton reel fits snuggly in the hole in the middle of the plate attached to the chassis. The rod, cotton reel and spring form a sort of McPherson strut locating the rear of the gearbox. There should be a rounded washer half-way down the rod that forms a friction damper against the cotton reel. Depending on version, this washer may be located by a shoulder on the rod and a bush below, or a couple of bushes either side. It's all about decoupling the mass of the engine, gearbox and front suspension from the passenger compartment.

[iRS]

Paul
Many thanks for the quick reply. That's helped me quite a bit. I have now fitted CAC3227 into the plate - a bit of struggle to get it in, but its there now. I still feel there are a few bits missing - I can only assume that it wasn't assembled correctly the last time this was touched on the car. I have ordered C30157 and C29011(spacers and damper washer) so those should help. Does the tie plate sit directly below the cotton reel or should there be something between them? There's also a large special 'washer' - to the left of the rod in my picture. Where does this go?
Many thanks.

[PaulGover]

AFAIR, on mine there are a couple of washers shaped a bit like upside down dinner plates either side of the cotton reel, but at least one of them was part of the relevant bracket. Unfortunately, while the general design is the same across the years, there are individual variations. The larger dished washer in your picture looks like it goes above the cotton reel, with the bracket being the lower side, but I've no idea where the smaller one goes - perhaps above the bigger one.

There's a picture for one variant in Kirby Palm's book (google for Kirby Palm "Help for the Jaguar XJ-S owner" to find it) and a discussion of others. (While there's an awful lot of good info in it, IMHO there's rather a lot of brute-force-and-ignorance in some of the recommendations. Pick and choose carefully, and remember that contrary to often stated views, Jaguar's engineers were smart.) If yours is missing bits, you'll probably have to try assembling, and if it doesn't look right/sit evenly distributed about its mid-point, tweak it with some washers.

I'm a bit surprised you need the damper washer - your photo of the remains of the cotton reel shows an indentation in the middle that looks like it had one before it fell apart.

[Popsjag]

Hi Roger.

Is this any help to you?

[iRS]

Thanks to you both. I think I am nearly there now. I have managed to get two spacers and the washer from Jaguar Classic through the local Jaguar garage. It makes more sense now with these. My only remaining query is whether there should be a washer below the cotton real and above the tie plate. PopsJag - which model does the diagram represent? I see there that there is a washer below the cotton real.

[Popsjag]

Hi Roger,

This diagram is supposed to cover XJS vin no: 139052 to 226645.

Regards,
Steve.

[keri]

I have attached a picture of the 1975 xjs factory manual set up I just did mine on a1975 auto and it is very similar large washer at top then 2 spacers and small washer between and the smaller washer of the big 2 c30159 the other side of cross member the cotton reel bush pushed through hole in x member so 30159 is on the bottom of the bush and this washer should fit easily into the x member hols so it can move up and down then the support bracket c4197 then nut see pics I have attached of my car so it gives you an idea.
keri

[PaulGover]

Thanks for the pictures; unfortunately it's hard to tell from them, though there's nothing dramatically wrong.

I hope I'm not leading you astray, but I think the diagram you have (which is like the one in my manual, so I think it's Jaguar's problem) is misleading. It shows the two spacers C.30157 with a small washer C.29011 between them, and about the same diameter. It also shows the washer with a rounded outside edge C.30159 below them.

From what I remember of my late V12 mounting, the rounded washer C.30159 is a little larger in diameter than the spacers, but a fair bit smaller than the hole in the cross member where the cotton reel sits. What I recall, but this is from several years back, is that the C.30159 should sit between the spacers C.30157, and probably the small washer goes at the bottom. The intent is that the rounded washer gets forced into the cotton reel, so it compresses the rubber. When you drive over pot-holes and the like, this compression causes the cotton reel to act as a friction damper to stop the gearbox and mount bouncing up and down.

So if the washer between the two spacers was no larger in diameter than them, and if the rounded washer at the bottom is a bit bigger but still capable of being pushed into the cotton reel when mounted in the cross member, they might need swapping. But if the one between the two spacers is larger diameter, then it's probably correct.

I think when I first reassembled mine I got something wrong, and it ended up sitting at one end of the spring's travel resulting in no upward or downward movement of the transmission, which sounds similar to yours. I wish I could remember what I did wrong!

For what it's worth, my transmission makes a noise when I turn hard right, which I think is it leaning against the chassis leg on the left under centrifugal force. I suspect my cotton reel has dissolved. When I get around to replacing it, I'll take some photos, but I doubt it will be soon, especially if we get a cold winter.