XJS differential question.
 

I was under the impression that older XJS's all had limited slip differentials in them, however after taking apart '86 diff yesterday, I found no evidence of locking in it. Please see the picture below.
My original diff is late 1982, the HE model, does it have limited slip, or also no?

Hm. My understanding is that they were all LSD, I'm very interested in hearing more about this.

I'm finding low production cars are quirky. Few sources agree, and few people test them. Also, with the age you have to ask if the differential is original?

Yeah, never can tell if there was an oddball mistake or exception on the assembly line but the more likely story is that the diff was swapped out with an XJ6 unit....very few of which had limited slip.

Cheers
DD

Well, I am taking mine down today and I will see if my original '82 guts are any different.

Hey Mish

The ROM only lists LSD so I think Doug is on the money.

The Dana 44 hemisphere will fit in the Jag diff. the bolt holes in the flange are smaller but these can be drilled out for the Jag crown wheel. Or you can use Dana gears but the pinion yoke is different and you will need to mod the drive shaft.

cheers
Warren

Yep, just pulled my original rear off the car and diff looks different, even from the outside. I think someone on eBay is about to get negative feedback, for sticking me with XJ6 rear end.

What's up with your original diff? Why did you buy a replacement?

cheers
Warren

I got entire rear end for $350, since mine was all surface rusty. Now I am gonna make one good one out of all parts.

Ok, $350 sounds like a good price. I would rebuild the original diff. Do you know what ratio is in it? XJS came with 3 ratio choices 3.07, 3.31 and 2.88

Mine had 2.88 and I have just installed 4.09 on the original carrier with a custom spacer. I have also had additional shims installed to tighten up the LSD. I have just bought a complete XJ40 rear end for $40 for the 3.54 gears just in case the 4.09 is too short.

If it is only surface rust sandblasting and powdercoating the LCA's, subframe, radius arms and all other little bits works well.

Well, I am building hybrid, using my original LSD - 2.88, drive axles, frame and radius arms from purchased rear end. I will check which shocks and springs to use, but it looks like mine were replaced with red Koni's, when bought rear end has some good black, no name shocks on it. I will clean, prep and paint all parts, to make her undergarments look pretty.
My questions are:

1. Each of my differentials, has different shims, where drive axles connect. Do I use same shim setup, based on what diff it came with, or what frame / axles / radius arms I am using? I am building hybrid here...

2. I have solid fulcrum bearings in my rear hubs and original needle bearings in bought one. What is better options here, both are in great shape.

Thanks again!!

Shims where the drive axles attach to the diff, on the outboard side of the brake discs? Those are camber adjustment shims. I use the ones that go with the frame, shafts, and hubs....but when it's all said and done you're gonna wanna have the camber checked and (possibily) adjusted anyway.

The shims on the inboard side of the brake disc, by the way, are for centralizing the brake disc within the caliper. That's something checked and adjusted on assembly.





I dunno. I have no experience with the solid bearings so no basis for comparison. The needle bearings are fine and last forever IF the seals are good and/or they're lubricated regularly.

Cheers
DD

Shocks are probably Boge these are black and came standard.

When you push the new large bushes into the raduis arms turn them 90deg so that the holes are sideways to the arm, this will firm up the bush.

As Doug said the shims set the camber. and All of the above. The camber is set by the relationship of total length of the LCA and driveshaft, changing anything can and mostlikely will effect camber.

I asume you are refering to the inners, use what ever is in there then. I would also pull the outer fulcrum bearings from the hub carriers and check them for signs of wear on the cup.

Sorry for jumping in on this thread, but is there a way to determine what gear ratio there is there? Is there a tag? Or is it year-specific?

Usually there is a tag if it has not been removed, it will have the number of teeth listed like 49/17 which is 2.88.

This is what I saw when I dropped my rear end. I am a total newbie at this BUT when I realized I am capable (it took a long time for me to build the courage to drop the rear end) it led me to more questions.

EBC9420-28E. I understand this is a 2.88 differential...?

Is there a way to up the ratio with the equipment I have OR does one just have to go find/purchase a diff with the higher ratio?
https://cimg4.ibsrv.net/gimg/www.jag...44a1e6decc.jpg

Yes, that is a 2.88. If you're patient and follow the manual exactly, you can rebuild it with a different ratio, you'll need the crown wheel and pinion, as well as a different carrier. There are carriers for 2.88 and numerically smaller, and those numerically larger than 2.88 (3.08, 3.54 etc). The carriers can be difficult to find, but the guts are interchangeable back to series 1 E Types, so you might find an e type guy who wants a 2.88.

I used the center section out of a very early Xj40 which was 3.54, but USA market XJ40's got 2.88, which rest of the world cars got 3.54.

Points:

1. Turn the input flange on the differential. If the hubs turn in the same direction, it is limited slip. If they turn in opposite directions, it is an open differential. or the slip clutches are gone///

2. Ratio. Turn the input one time. How much did the hub turn. Almost a third, a third or a bit over a fourth??? do the math?? or is it draw a conclusion?

3. My lump is quite happy with the 2.88. And pulls OD well. .70 X 2.88 is pretty tall!!

Carl

Ok Jagboi! Thank you.

A few questions. And I hate to do this to ya, lol

--- How do I begin searching/shopping? Ebay searches or should I try going to some of the different areas of the forum? Which would apply...

--- in general, what are the benefits? Is it harder or easier on the trans and engine,,, increased mpg? Faster!?!?!? What are pro's and con's?

--- is it TERRIBLY complicated,,, or does it just sound that way? If I started googling or youtubing "differential upgrades" would I get a sense OF are things about the jag rear end that are specific and unique?

I think I want to start looking for parts.

I don't want to wear you out BUT I would love to hear your thoughts,,, might even pay ya for em 😜

Open to all input.

Y'all are GREAT!

There are a number of places to shop: wrecking yards, ebay, places like David Bodger ( everydayxj.com) etc.

Benefits: This is one of those things where there is no right answer, it depends on what you want from your car, your driving style and what you want to do. In general a numerically higher (like 3.31, 3.54 etc) ratio will give faster acceleration at the cost of higher cruising revs, so more noise, heat and lower fuel economy. A 2.88 is the reverse: slower acceleration with the trade off of more relaxed cruising and less fuel use.

If your car is a track car, then you might not care about fuel economy or noise, to obtain the benefits of faster acceleration. A sunday driver might be the reverse. Basically Jaguar was working within the constraints of the 3 speed automatic and chose 2.88 as a good all around compromise, as did many other car makers. Piston engines generally achieve minimum fuel consumption at an average piston speed of about 7 m/s, this is true from lawmowers to large ocean going ships, and with the 2.88 axle the V12 comes close to this at 70 mph cruising speed. Back in the late 70's when it was designed, these axle ratios and the HE engine were designed to achieve maximum fuel economy at cruising speeds up to 80 mph.

When Jaguar changed to the 4 speed overdrive transmission, they went with the 3.54 axle to give better acceleration, but when combined with overdrive the cruising revs are nearly the same as the 3 speed/2.88 combination.

Rebuilding the differential will take some special tools, it will take a number of different sized shims, and above all patience. You must be through and methodical to be successful. You'll also need to be able to consistently measure to thousands of an inch. The bearings will need to pressed on and off a number of times to get the shimming right, so you need a press and the special bearing puller. The limited slip mechanism is very different to what is found in most US cars, although some 60's Chryslers used the same system.

If you want to change ratios, it's probably cheaper and easier to get a complete diff or rear end from David Bodger than to rebuild one. Between special tools and parts I spent well over $1k doing my diff rebuild and that was getting a junkyard diff as a core and using the gears and LSD components from it.