97 Jaguar XK8 - "Kate" needs bottom filler

back to more mundane things - Caliper re-furb.

The rubbers can be difficult to get in and using a similar tip I picked up from a Jag forum I used the lid of an Aerosol can cut town to about 20mm.The piston just slides nicely inside it.



Load the piston end of the rubber onto the plastic and the caliper end fits easily into the cylinder groove, slide the piston almost all the way in then pull out the plastic and the upper seal drops into it's groove. Took a minute.

I am by no means an expert but I thought it was only the S-Type TDV6 (Diesel) manual gearbox that fitted the V8?

Changing diff ratios on the Jag IRS in XKs is no big problem. It's the same bigger diff case as you get in XJ40s, X300s and X308s, but the diff centres will fit from the early type too (there may be some fettling to get the 2.88s to fit, but SimplyPerfromance did mine).

Shouldn't need a quaife diff either. Plenty of LSD options available for the Jag diffs from the factory. The earlier types as fitted to Series XJs and XJS' is a better design, but the later XJ40/X300 types work fine when in good nick (mine certainly did).

By the looks of things the S-Type 2.7 gearbox has comparable ratios, but a much better 1st gear. 1st on the BMW 'box is stupidly short (5.08:1), which means there's no legs to the gear and a big step from 1st to 2nd. Good for towing, but not much else. Compared to that the Jag's 4.68 1st is much nicer.

Don't see why you'd need to change the diff ratio though. The 6-speed is decently overdriven, so with the 3.58 diff I think you have you'll be turning 2600ish at 70mph. Not great for a diesel, but perfectly fine for a petrol. If that's an issue then there's 3.07 diffs for 2200ish and 2.88s for 2100rpm.

I think I found the S-type gear ratios,
4.68
2.53
1.69
1.22
1.000
0.837

I put them into this rather excellent calculator www.blocklayer.com/rpm-gear.aspx , with the XK8 final diff of 3.06 and tyre diameter of 28" - saved results apx6u.app.goo.gl/b7Fz
2600=70 in 5th
if you are shifting at 3.5k it looks like this (if I have the numbers right!)



So that looks pretty good to me!

That is a cool calculator!

Gear ratios look good to me definitely more evenly spaced out than the BMW ratios.

Might have come up with a solution for the missing autobox electronics, it's all theoretical but it will be good if it works. Breaking out the Arduino and CAN interface next few days for some try out.

Meanwhile something that was not flagged on the MOT but that I can see being an issue if it gets worse is the O/S main beam reflector has lost half it's Chrome. Used lamps sets are £200 and so far no luck finding just a reflector (real or can be made to fit) so I'm thinking chrome vinyl wrap or chrome paint over black gloss.  - I did try with a metal film tape that I have- as it is a  thin film of Ali it can be polished - it was "OK" but can do better I think.

Apparently there is no perfect solution other that a few hundred quids worth of kit to DIY or the same in pro service.

Someone has replaced them with Hella 90mm units hoping to get some more details on that as it is an upgrade as well. Alternatively an ebay breaker has one for daft-ish money. MOT is not until 7th so time to experiment..

Burned the mains for 30 mins - no issues with the wrap - if anything the heat smoothed out more wrinkles !



Condensation is an issue in these light units and Jag issued a TSB to drill a 9mm hole in the side and add a bit o pipe. I did this to the reflector fix side but no difference to the condensation forming even as I burned the mains.

I have seen a few other solutions involving silica pouches or cat litter (- appropriate), but I would rather ventilate than accumulate. I cut a 30mm hole in the clear top cover for bulb changing, it's tucked up under the bonnet but I uses silicone to stick on a patch of roofing membrane that (like Goretex etc) is breathable but water proof. Run it under a tap and nice and dry.

Many moons ago I was responsible for developing a fix to this problem on a similar headlamp, the key is to place the lower air vent in a high presssure (but dry) area and the top one in a low pressure area, one thing to avoid is pulling air off the back of the radiator, in wet weather this contains a lot of moisture.

When stationary the heat from the lamps will induce some flow but if designed correctly they should clear much quicker when driving.