Hello everyone,

So my recently acquired xjr is making a low huming noise when I'm coasting on the throttle, if I release the throttle or get on it the noise goes away. I looked under the diff and there is gear oil grease so apparently I have a leak and I understand fixing the leak is a royal pain so I was planning on buying a used unit and putting new seals in it as opposed to messing with rebuilding the gears/bearings. I was wondering if there is a better rear end I can get from a different model or year, I'd like to get something more durable and with more aggressive gears if possible. Thoughts?

Thanks for your help you folks are as classy as our cars.

 

I'm not aware of anything stronger that would bolt in. Mine failed at 77k miles.

The standard 4.0 XJ6s used a 3.58 ratio (versus your 3.27). Should be no problem finding one of those although I question the plan to install a used diff without rebuilding. These diffs don't have the best reputation and you may end up with a unit no batter than what you have.

Lots of labor to do the job once, let alone twice.

Cheers
DD

 

And your X300 diffs are supposed to be heavier duty than the later X308 diffs

At least if you replace the bearings you have new bearings as opposed to new seals on old bearings.

 

The diffs in the old inboard-brake cars were nigh on bulletproof...well over specified for the input they were subjected to. When they failed it was usually due to lack of lubricant----hard-to-replace seals can be left leaking but you gotta remember to top-off the oil now and again :-)

Rear hub bearings, too, were much less of a problem on the old style IRS. <sigh>

Cheers
DD

 

However, apparently brake jobs were a real joy

In this particular case, the OP mentions the usual greasy sludge. Perhaps cleaning the breather and a full drain/refill might solve the problem. Cheap and easy as a first try.

 

I replaced the diff in my XJR late last year there was nothing wrong with my old diff as it had been rebuilt at 160 .000 k,s and the car had only done 220,000 when I changed the diff
The reason I changed the diff is I wanted the 3,58 gears the 3,27 are to tall unless the car is on the highway all the time
The 3,27 gears are worth money as they use these in XJS cars to replace the 2,88,s they come with from the factory makes the XJS cars come alive and so does the 3,58 gears in my XJR
I have seen much higher top speeds in the car with the 3,58,s than I ever did with the 3,25,s not to mention the car is nicer to drive around town and if I get a little rice rocket next to me with junior on-board thinking smart
I hose him of very nicely the look on their faces when they just got hosed by a jaguar is priceless
I also have no problem keeping up with a whole range of newer cars admittedly I have a full headers to tailpipe exhaust system and had my computer remapped by Andy and cold air induction of some sorts as well as modified inter-cooler pump but none of this made as much difference as the diff gears
The diff is pretty simple to rebuild just have to make sure when you are doing the pinion that you don't over-tighten the pinion bolt as these diff use a collapsible spacer and once over tightened are stuffed
I set my diff pinion up then had a solid spacer turned up should last forever
I also used redline shockproof oil when I did all the mods don't want to be looking at the diff for a while

 

Taken on any Subaru WRX's in good tune lately? Or how about a Mk IV Supra Turbo?

 

A few years ago a WRX driver and I diced it up on some twisties one Sunday morning when we had the road to ourselves....although I don't think it's what he originally intended. He pulled in behind me and obviously wanted to go fast and get around me. I made him work for it....or so I thought.

We had fun for a few minutes minutes exchaning lead/follow positions until he became bored and disappeared like pricked balloon.

I was exhausted. Pretending a big Jag is nimble is hard work :-)


Cheers
DD

 

Must have been like the time I was out to "test" new suspension settings on a 2nd gen TransAm at 2am on some canyon roads.

Waited at the usual spot for traffic to clear, which is the semi-responsible thing to do ... including the last car which was a TR-6 that went buzzing by. After 20 seconds ... I thought screw it and took off after him. He saw me come up on his tail and downshifted. So I let him get 50 yards ahead and then reeled him in again. Did this 4 or 5 times before just pulling around and punching it. Nothing beats cubic inches

Beautiful exhaust note though ... as we said before

 

Thanks everyone, just a couple of follow on questions. Did the regular xj6 have traction control? Did all xj6s have the 3.58 rear end? Are there rebuild kits available or do I need to buy each piece individually? Where would you recommend I get the parts?

 

Coventry West specialises in rebuilding Jaguar diffs. They may, or may not be willing to sell you the parts.

 

thanks plums I just called over there and spoke to Pete they'll sell me a locking diff for $700 after core which isn't bad at all. They'll sell them with a 3.58 or a 4.09 ratio, anyone have any thoughts or recommendations on that ratio? I'm not planning on doing a manual transmission swap to benefit from more gears or anything like that.

 

Also how do I compensate for the bigger gear in order to not throw off the ABS/Tranction Control system? is there a revised speed sensor I can use or do I need to reprogram the computer?

 

Good price, but don't commit until someone who knows tells you that your ABS will be okay.

 

I went from 3.27 to 3.58 and didn't recalibrate anything...and ABS and trac control seem to work just as before.

Not that mine is the final word but, AFAIK, neither the ABS nor trac control sysems know or care what the gear ratio is. I think the heart of those systems' calculations is wheel speed....and the wheel speed sensors don't know what gear ratio is installed either.

Cheers
DD

 

I'm happy with the 3.58. Good improvement in response but not obnoxiously revvy at highway speeds

Personally I think the 4.09 would be too short. Too busy and may actually sorta defeat the XJR/6s near-prodigious low and mid range torque

There's also a 3.77 if you wanna split the difference. Not sure if CW has any in stock

Cheers
DD

 

Optional on the base XJ6.






That was the standard ratio for the 4.0 XJ6s with automtatic transmissions. I seriously doubt that any of the USA cars were fitted with any of the alternative choices

Cheers
DD

 

Had a run against a 08 WRX about 5 months ago the look on his face when I overtook him at 245 k,s per hour was a nice feeling (LOL)

 

I was going to buy one of these before I swapped my 3.27 for 3.58,s www.motorcarsltd.com/JLM1922-38R.html seems reasonable for re-manufactured
the cost to Australia was 200 dollars not sure where you are in the world I have bought quite a few things from these guys and very happy with all my purchases

 

By all accounts, your XJR has had extensive work done on it. So you're saying you overtook at 150+ mph then? In overdrive?

Without overdrive, on 26 inch diameter tires with your 3.58 ratio that would be just a hair over 7000 rpm.