anti seize on the splines ...... excellent ....top job Greg

 

Jack
The racing XJSs used standard driveshafts, if I remember correctly from Allan Scott's book. However, as the engine capacity and much else on the engine was fixed to factory OEM spec, the TWR racers were at about 400 BHP from memory. Believe it or not, I have heard of cases of the driveshafts being twisted. Have you heard of Dax Cobras? These are a really top spec Cobra kit car that loads of people race in the UK? They use Jaguar rear axles, but because the track is narrower than the XJS/XJs, they actually cut the lower wishbone and weld in a tube, I think, and they claim the welded item is stronger than the original. What they do with the driveshaft I do not know, but maybe they do something similar? It would be worth asking them, I think, or some racing shop in your country.
The driveshaft is a forged item and extremely strong, and exactly how you reinforce a forging and make it strong afterwards I do not know; but someone will. If it was me I would suck it and see, and have a few extra driveshafts ready in the shed!
Good luck with it anyway
Greg

 

Thanks Greg. I had pretty much decided to do what you recommended, and see what I break first. I had hoped to find some interesting reading, on how "they" did it, before I find the "Weakest Link" so to say. I'm still away's from that, as I'm almost done replacing the rusted sections of floor, and then welding the 1/16th thick panels in over them to add some more strength. Once the floors are done, I'm gonna start on the area around the trailing arm mounts and reinforce them as well. Then I'll add some radius arms to the rear cage, similar to what Ronbros, has done to his. Thanks for the help as always.

Jack

 

Jack
This is worth a read, it has lots of useful info:

 

Regular readers will recall this thread:
https://www.jaguarforums.com/forum/x...shimmy-209068/
and this thread:
https://www.jaguarforums.com/forum/x...ox-xjs-221677/
In addition, I had also a few months earlier had a problem with my "dog bone" castings - that bolt to the side of the diff and hold the lower wishbone inner fulcrums - coming loose. Described here:
https://www.jaguarforums.com/forum/x...ration-193055/

The first two threads were motivated by a search for a mystery front wheel shimmy, but I mention the third as I have an idea (actually Grant had the idea!) about them all being linked to the ultimate cause of the vibration and shimmy. In both the first two threads' cases, the shimmy was reduced, and I thought I had cracked the problem, but in both cases it returned, at a different speed, or in a reduced form, but it had NOT gone.
The gearbox swap was partially motivated by a distinct sound that appeared under certain conditions and was for sure caused by the torque converter rotor just touching it's outer stator. And I did find fine metal articles when I flushed out the tranny oil cooler.
Anyway, although all this work did help and did ameliorate the problem, and I thought it had been cured, back it came at about 120 to 130 kph. No ignoring it, I had to fix it if I was to enjoy the car.
Long discussions on the France/Oz hotline came to the conclusions that the only thing that was left was the UJs in the rear axle (the propshaft had been renewed a year or two ago).
The vibration has now, for 100% sure, gone. The rear axle UJs going home were definitely the ultimate fundamental cause of all the symptoms. Essentially, I believe the process was as follows:

1. the un-smooth rotation of the axle caused the tail of the gearbox (at certain speeds only) to oscillate side to side,
2. and this in turn caused the entire engine/subframe/suspension - as a a unit - to oscillate side to side about the front six-shot subframe mounts;
3. While the subframe was moving side to side the front wheels' gyroscopic action kept them going dead straight - so this caused the rack to move to take up the side to side motion of the subframe and thus the steering wheel was moving - even though the wheels were going straight. This steering wheel shimmy caused not by the front wheels moving; but by the engine/subframe/suspension unit moving!
4. the OEM six shots having sufficient compliance to allow the entire engine/subframe unit to "wag".
5. The changing of the six shots to poly changed the harmonic and the vibration disappeared at 80 kph and reappeared at 125 or so.
6. Once the axle UJs were changed - and thankfully the evidence of very substantial wear once they were apart was obvious - the entire problem disappeared, at all speeds tested well into the red sector.
7. Finally, it is important to note that the UJs showed no obvious symptoms of wear before they were dismantled. There was no noise, no looseness, and they had been regularly greased. But this is what the wear looked like when they had been removed:

And here is the punchline: I am certain, as suggested by Grant, that the loose dog-bones were the first symptom of the UJs going home. The dog-bone bolts had been shaken loose by the UJ-caused vibrations. So if you have loose dogbones, change the UJs as well as fixing the 'bones!

I had no idea that this engine/subframe/suspension unit oscillation was happening and for about two years proceeded to address the symptoms and not the cause. Including a brand-new subframe and all new front suspension components. Well, at least it is all new now, even if unnecessary...The new gearbox was necessary, thank goodness, otherwise I would feel even more foolish about this entire process than I do now!
I hope this may help others in the future, at least.

 

Thanks Greg. I hadn't even thought of all the twisting that can happen in the suspension of the XJS??? It is a far cry from all the American Muscle Cars I'm used to, where everything is attached to the frame with a few mounts, and a couple bushings, and has a solid rear axle hung from the frame instead of a separate cage and IRS. The swing arm style, engine cradle/front supension unit is also very unique. It'll be interesting to see what it "all" thinks of 650Hp. LOL!

jack

 

Jack
TWR bolted the subframes front and rear solidly up to the body. No rubber. As you are, (in effect) raising RWHP by more than 100% from OEM, I think it would be sensible to do the same!

 

I had thought about that a little bit, but I figured it would detract from the smoothness, and overall feel of the XJS? Even though It's been some 40+ years since I drove one, I still remember the smooth, refined, sneaky feel, as it handled, went like stink, and road like a luxury car, kinda the best of both worlds. And I'm not really sure if I want to disturb that feel. I'm also not sure of what it would take to accomplish that? I haven't got that far into building yet. I'm finishing the floor pan repairs, before I move to the trailing arm mounts and the suspension assemblies. I will definitely look into this much more intently, as you have raised a great concern. Thanks. It is appreciated as always.

Jack

 

You are quite right, it will ruin the feel of the car! It is just that I am not sure that the OEM rubber will take 600 RWHP!

 

Yeah me either???????????????????????

Jack

 

UPDATE:
I found and bought two 90 degree 1/4 UNF threaded grease nipples here:
https://www.advancedfluidsolutions.c...490-1947-p.asp
Luckily this turned out to be the correct thread size, and the nipples do NOT foul the hub carrier.
It is, however, important to place a washer of about 3 mm thickness on the nipple threads, otherwise the nipple is too low-set to get a grease gun onto the nipple, as the edge of the yoke fouls the gun. In the above photo, you can see how the surface of the UJ end-cap is quite a bit lower than the end of the yoke. Also, of course, the nipple must be tightened with the nipple facing inwards along the driveshaft! To get it right and decently tight, I used a spring washer on a 2mm flat washer.
Greg

 

Just for completeness, I realised I had not posted on this thread exactly how i measured the endfloat/preload in order to select the required size of the phosphor bronze spacer. I recently posted on the E Type section as follows, in case anyone will in the future find it useful:

Just in case it is useful, I have dug out a few detailed snaps of the measurement of the phosphor bronze spacer:

This is the view of the inner side of the hub carrier. The bearings are in it, and the hub has been inserted too. The pointer is on the INNER race of the inner bearing.

In this snap, the pointer is on the inside end of the hub tube, that rotates with the driveshafts and into which the splined end of the driveshaft goes.

The useful end (for measuring depth) of the electronic caliper.

The caliper is measuring the height difference between the inner end of the hub tube and the inner race of the bearing. It is this height difference that must be filled by the phosphor bronze spacer. Doing up the castellated nut on the driveshaft, means the bearings are tightened to the required preload/endfloat, but no further, as the spacer transmits the torque to the driveshaft inner flange by the UJ.

Once measured, select the required width of spacer. Endfloat/preload should be 0 ideally, but anywhere between +2 thou to - 2 thou is fine.

This final pic shows what the spacer is being torqued against on the driveshaft UJ flange. The large chrome spacer acts as a spacer, but also provides a surface for the oil seal on the hub carrier inner side to run on:


__________________
Greg: XJS V12 1985

 

I always come back to Greg's threads since they are very informative and a good reference as I rebuild my own IRS hubs.

Greg, do you happen to have the part numbers for the inner and outer grease seals for the hub, as well as the seals for the lower fulcrum shaft on the hub? Those are the ones that cover the small tapered roller bearings.

 

nsogiba,

Remember, all part numbers are on Jaguar's parts website. Here's the pre-facelift hub page:

Genuine Hub And Carrier-rear For Jaguar Xjs Sports Coupe/convertible 1975 - 1996 Classic | Jaguar Land Rover Classic Parts

Cheers

Paul

 

In my case the bearing seals came with the bearings that I bought from Manners.
They also sell a hub lower fulcrum kit with everything in it.
Paul's link is so useful, but at 71 UKP for an outer oil seal, I do not recommend you buy!
Thanks for your kind words of appreciation!