Hi Plums I have 245/50/17 tyres on my car makes the speedo exact and since fitting the 3.58 diff I have seen higher top speeds consistently than with the 3.27 the car now gets there instead of wasting time trying to get there
The car does make a lot of noise when its at that speed I have a plate that blocks the extra holes in the supercharger so the supercharger is more like the ones fitted to other M90 equipped cars the supercharger whine is a little bit unnerving as is high wind noise and the car itself tends to get a bit of panel vibration as well at high speeds
That,s maybe why the WRX might have let me get past him the engine felt fine at that speed I am also not looking at my instruments I am looking at the road only quick glances at the instruments
If I could get the car to lock the converter and overdrive and I could then get the car on a flat road I could do the calculations for theoretical top speed
My next spend is the transmission I want to try and reprogram it so its not coasting when I take my foot of the throttle more converter so it makes use of the engine braking more and not shift down so much when you get on the throttle as the torque is there now with all the mods engine feels really strong considering the 240 thousand on the clock it had had a lot of engine work before I bought it in 2008
I have had to slow down a bit now not many points on my licence and the boys in blue over here are on the warpath about speeding

On another point if I had the time and money to spare I would have gone for 3.7 diff gears just for a test as the 3.58,s have only moved the RPM about 350 rpm up the scale while on cruise control 3.7 might have moved it 500 or 600
It depends how much open road driving you do most of my driving is highway from the Gold coast to Brisbane about 120 k,s of 5 lane motorway each way
Now that its summer and holiday season I use my 200 cc scooter to go everywhere I need to go at home no trafic or parking problems and no k,s added to my car which I intend to keep for a long while although it uses no oil or blows no smoke at current odometer reading a big statement for a car that old just goes to show better buying them with good history than not
And sorry for changing the diff gears subject
I personally would change the diff gears I have done this to a few cars over the years if you need to fix the diff anyway time to change the gears at the same time

 

Coventry West doesn't have any 3.7's in stock so its looking like a 3.58 is it, there is a guy parting out a 97 xj6 with traction control, he says his rear end is good and will sell it cheap, I was thinking of buying it and resealing it and installing it. Thoughts? Have any of you resealed these units before pinion seals and the output shaft seals? Any special tools necessary?

Also based on what I'm reading from doc if I swap my tires for 245/50/17's I won't need to worry about speedometer calibration.

Thanks everyone this information has been very helpful.

 

My speedo was always out by 8 k,s the diff gears made no difference because the speedo is driven by one of the rear wheel sensors so your speedo shouldn't need recalibrating I played with tyres to get the speedo exact for the speed cameras (LOL)

 

Badass!!!

 

I see thanks doc. Has anyone replaced the seals in these diffs before?

 

So the guy parting out the xj6 locally is selling me the whole rear end assembly with good axles and suspension for $350 total thoughts?

 

Has anyone replaced the seals in these diffs? is there a procedure?

 

At the top of this section, in one of the sticky threads, is the service manual download. From there you can go to the "Driveshafts and Final Drive" section where the seal replacement procedures are described.

Cheers
DD

 

great thanks very much Doug, I've been searching the forum to figure out the procedure for cleaning out the breather but no luck, can anyone point me to that?

 

Huge thank you to MotorCarMan and other users at the following link:

Check out this link for breather pics and location, I'm sure you will find it helpful:
https://www.jaguarforums.com/forum/x...st-seal-55403/

I must do this as well.

from ixj8it:
Image From Motorcarman:

 

Sweet thanks guys

 

I should note that the part number that appears on the image I posted (JLM20323) refers to the differential breathers after 1998.
It may likely be the same part as 1995-97, however, the actual part # for those 3 years is JLM631.

 

Got it thanks

 

Would I be able to use the ring and pinion off a xj6 non locking and somehow use my diff with the locking and 3.58 gears? I happen to have the ring and pinion available to me.

 

Hi Doc,

I'm impressed! I rebuilt the diff in our '93 and getting everything right was not what I would call simple! You must be quite a mechanic!

I'm very curious about the solid spacer you had turned up to replace the collapsible spacer. A solid spacer may or may not wear any faster than a collapsible spacer, but from the wear I observed in our diff it seemed to be the pinion bearing and race that had worn to the failure point. If it were the collapsible spacer that wore, couldn't we just tighten the pinion nut to compensate over time. What am I missing?

Below are links to photos of my rebuild of our diff, plus the output shafts and removal/installation of the diff and IRS.

Cheers,

Don

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The collapsible spacer is designed to collapse to a point to give the correct pre-load on the pinion bearing when the bearings wear they wear like most diff,s

If you retighten the pinion as some people do you risk the chance of over tightening the pinion and will overheat the pinion bearing causing premature bearing failure

The reason I used a solid spacer was when I give my car a thrashing that the lash or pinion crown-wheel gap does not allow the spacer to collapse further than the predetermined gap
My mechanic that is knowledgeable said they do that to Toyota hilux diff's when they fit V8 engines to them and use them for hard off-roading

I thought I would do it to my diff as I have no plans of ever having to rebuild it again

I also spoke to quite a few Jaguar guys that seemed to think the reason why the X300 diff's ended up getting problems was that they where under the car out of the air flow and got overheated that's why I used the Redline shock proof heavy diff oil as well

I also shimmed the LSD clutch tight as well

Wish I had this diff in my new X350 but that's another diff storey LOL

 

Hi Doc,

Thanks for the education. I'm still not convinced that the solid spacer will prevent the diff from needing a rebuild in the future since the pinion bearing is still going to wear....

I agree on the Redline - I've used it in the past and they also make excellent transmission fluids.

I have to wonder about the airflow theory and differential failure - it seems like lots of RWD passenger cars have diffs mounted in a way that they receive limited airflow.

My theory about the issues suffered by Jag diffs is that in the Jag IRS design the diff is an integral part of the suspension. The axles are the upper links, so there is tremendous stress on the output shafts and their bearings, and the way the diff and driveshaft are mounted with rubber bushes allows them to move in relation to each other in ways that stress the pinion bearing to a greater degree than in suspensions where the diff is more rigidly mounted. The Jag IRS is world-renowned for its superb performance, but the differential bearings pay a price for having to withstand the additional stress.

That's my theory, anyway.

Cheers,

Don

 

I was able to pick up a locking diff off a 94 xjs, but it is stamped with 3.54 and not the 3.58 everyone has been talking about. Has anyone have any thoughts or information regarding the 3.54, the xjs had the gm transmission and 12 cylinder engine. Thanks.

 

So I wonder why they put the taller gearing in the XJR?

Could it be because the 255/45-17 XJR wheel/tire combo was 2.28% smaller than the standard sized 245/50-17 wheel that apparently is almost spot-on to the 16 wheel/tire XJ6 diameter?

Maybe with more power Jaguar thought the higher gears weren't an issue and would help with gas mileage?

Curious....

.

 

According to XJRengineer the *only* reason XJRs had the 3.27 diff was to get a sub-6.0 second 0-60 time with the manual transmission cars. Press releases and all that. Using the 3.58 would mean two shifts to make the 0-60 dash rather than one.

As it turned out the manual trans version wasn't popular with only about 200 being sold. But they still got bragging rights.

Cheers
DD