So I’m doing a transmission mount rebuilt and filter/fluid change on my 89 XJ-S V12.
My mount came apart with a lower rubber spring mount cup and no upper. Bushing was pretty much toast (as expected given the noises during acceleration while turning hard right).
The kit I ordered from Jagbits came with 2 spring cups, presumably one for the upper and lower side of the spring. Searching the archives it seems like some people use one spring cup and others have two.
Any opinion on which is correct? Parts manual only shows the lower. Spring has some slop if installed with no top rubber cup.
Only result of installing both I can see is compressing the spring more and maybe increasing wear on the cups themselves.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
Ah, but it won’t compress the spring more! The spring will compress according to how much the tranny weighs. Adding a second spring seat will cause the tranny to sit that much higher, perhaps 1/8".
I think both seats are supposed to be in there. Whatever, when done the tranny should bounce a good ways up and down without hitting the end bumpers.
A stick shift for my XJS? I have been told that the bellhousing area readily accepts the General Motors bolt pattern, and wondered if I could bolt a GM 5 speed to the back of the V-12. If anyone in the group has tackled this project, I would appreciate their insights.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
4
You’ve been lied to. The GM 400 A/T has an integral bellhousing, and the bolt pattern where it mates to the back of the V12 engine is unique to Jaguar. IOW, GM had to specially make GM 400 transmissions for Jaguar. And in 1993 when Jaguar was renovating the V12 into the 6.0 liter version, they changed the mating bolt pattern to a different pattern that was unique to Jaguar! So GM was still producing transmissions specially for Jaguar. A conventional manual transmission bellhousing to fit either of those bolt patterns is not easy to come by, but a couple of aftermarket places have produced them. Conversion to a manual is a big job but well worth it IMHO, the car is a hoot to drive with a manual.
I just did mine (1986 XJ V12) not long ago. Both cups were there and both caps went back in.
Reassemble everything loose and make sure the transmission is able to bounce up and down freely before you tighten everything.
Did mine last year on my 1988 XJ-S, if you’re talking about the spring seats, mine only had it on the bottom, as evidence here is the diagram, which mine was identical to. The top of the spring sat firmly in the metal retainer up top.
Side note, I chose poly for both the cup and the bushing. Trying to get the main bushing inside the hole was challenging, but with some grease and strength, i did it by hand.
Well I ultimately decided to go with using a top and bottom spring cup!
Feels pretty tight, not sure if I have much up and down play. Either way its all back together but I won’t get a chance to refill the transmission and take it for a drive until Saturday.
gregma: I had the replacement rubber bushing, and it was no treat either!
Thanks, and I had a feeling that this would be too good to be true. I would still like to pursue the idea, and thinking it is a pretty large, and heavy, car, I just wonder how that would work? Now, the Series 3 E-types had a 4 speed, but I am betting that would be a hard one to come by, not to mention the cost?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
10
Even some of the E-type owners are looking to drop in a modern 5-speed Tremec T-5 or a Getrag. No good reason to reach that far back in history for something that wasn’t original anyway (note that there were roughly 100 early XJ-S’s made with the same 4-speed as the E-type, reputedly just to use up the remaining stock of 4-speeds.)
Besides, the tranny isn’t the problem. The bellhousing is the problem. And the flywheel, and the drive shaft, and the speedometer pickup, and the transmission mount.
So after input from everybody and having nothing but time on my hands. Decided to go with 2 spring cups.
One test drive told me I’d made a mistake. There was a significant increase in driveline vibration and noise. Decided to give it a day or two and a few more drives. Nope.
Disassembled the mount again and removed the upper spring cup. Much faster the second time around now that everything had been apart.
Yep. At least for a 1989 XJ-S V12, definitely only the one spring cup is required, the lower one, which lines up the parts diagrams. It was also much easier to reassemble with only one rubber cup in there.
Good info. I’m wondering what years two cups were used? Even XKsUnlimited sent me two saying I needed them, and I ended up sending one back.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
13
The mount on the BW12 transmission was completely different, although it worked the same way with the spool, spring, and rounded-edge washer. Perhaps it called for two cups? I dunno. Perhaps someone could take a look at the parts diagram for that thing.
I also have a very faint transmission noise, more like a rumble, and I wonder if this could indeed be the reason, but I fail to understand how the omission of the cup would make such a difference…
Theoretically it would just raise the trans by a couple of millimeters, very small difference considering that the mount has almost 2cm of up and down movement.
Plus the second cup should provide extra isolation.
What I noticed when installing the mount with 2 spring cups present vs only 1 was that the spring looked significantly more compressed. And the force required to lift that plate up to install the 4 bolts was quite strong indeed. In fact there was no way it could be done without a floor jack with the hole in the centre. I think the extra compression of the spring offsets the extra isolation from the extra cup. Also that cup was pretty heavily compressed by the forces involved.
So perhaps with the additional compression of the spring it is acting slightly more like a solid mount, and allowing more engine, transmission/driveline noise to be transmitted to the body structure.
And I would agree, the noise/vibration is somewhat more of a rumble, which is why I tried to describe it as driveline noise.
That makes me think, how tight do you torque big nut on end of stud that spring goes around? If you tighten too much, won’t that just compress spring/lower transmission? Since it’s a nylon locking nut, do you just put on until snug? No heavy torque?
I torqued mine on quite tight…may try loosening it a bit.
When you torque that big nut up, it pushes up on #18 in the diagram (tie plate, which is attached to the transmission), which pushes up on #21, (big washer/spacer) which then pushes on a #27 (sleeve spacer which is incorrectly illustrated for an early transmission without the wide portion of the post), above the sleeve (#27) is the round edge washer (#28, damper washer) which is sandwiched between the wide portion of the post and the sleeve.
Therefore there is a solid connection between that nut and the transmission. Thus the transmission is free to float on the spring, sandwiched between the big 4 bolt plate (attached to the chassis) and the post mounted to the transmission (#5). With the round edge washer providing friction in the rubber bushing (#3), to stop the transmission from bouncing excessively on the spring. Sort of a shock absorber / damper of sorts.
I torqued mine up tight as well. You could feel it bottom when everything came together solidly.
