This Jaguar is sooo not my favourite car right now


Driving to work one day I heard a nasty metalic noise- as if something from the underside had fallen off. I see nothing under the car. After removing the rear wheels, I see nothing untoward. When driving the car- there is a loud knocking noise that increase with vehicle speed and changes tone whether under load or not.
I sucked out the oil from the diff and checked it and there was no metal particles. I stuck a magnet in the diff to see if I could find any metal bits- nothing. I stuck the magnet into the transparent container with the oil diff oil to check for debris- nothing. I checked for wheel bearing play- nothing. I checked the drive shaft U joints- and they seem ok. I drive the rear wheel with the rear of the car in the air and the noise is certainly there.

At this stage I no longer have time to devote to this car. I give it to Eurotoys in Elgin to look at- and he suspects the diff.
I found out that the differential was already changed once in 2006 under waranty.
I talk to an old friend from Jag-Whitley who owns an X308 XJR and he's had similar issues. Another friend- who's ex Jaguar- filled me in on the diff. He worked in that department. He said that the decision to go for the 14 HU unit (as fitted to the X308) and carry this unit to the supercharged vehicle was ludicrous. He had opposed this decision but it was made by passionless folks who didn't care at all and just wanted to get the product out on time.
He said that for the XK180 concept car the older offset type 15 HU diff was used with powerlock- and its vastly stronger. He said on the 14 HU the teeth just fall off the pinion and the safety factors were just not high enough. This really upsets me. I don't see the point in getting another 14 HU unit. Waste of time cost cut engineering. On the otherhand, I don't want to fit a powerlock 15 Hu 3.58 ratio and spend $2K reprogramming the TCM.
I've been doing my research and the old hot rodders used to use the salisbury 4 HU units (as fitted to old series 3s and XJS') which had Dana 44 gear ratio interchangeability. There are plenty of Dana 44 gear sets availiable- including the required 3.07 ratio.
I asked my ex Whitley chum if I can use the gears from the older series 3 type diffs (4HU) into a 15 HU. He said no- because the XJS, old series 3 and even the Aston DB7 use a U joint on the prop shaft and the XJ40, X300 and even X308 use a jurid elastic coupling. I don't understand this exactly- becuase it seems to me that the Dana 44 gear sets have 26 splines as does the X308 prop shaft.

These websites have indicated that interchanging Xj40/X300 15 HU style diffs are possible.
REAR END SERVICE FOR CLASSIC JAGUARS

And this site even believes that the Salisbury/Dana44 style gears will still fit into the 15 HU casing.
Independent Rear Suspension Forum / XJ40 IRS - Boardhost Free Forums
And here-
XJ40 Powerlock

Russel-Rams post indiciated a high level of interchangeability.

I'm still doing research but welcome any other further useful information

 

setting up camp here

 

There seems to be an element of luck with these diffs, have no experience with different housings/gearings.

But you could also consider shot peening the original one for higher strength, than all you need is a very experienced diff builder that takes its time to set the pre-loads perfect.

Don’t understand your ex Whitley chum either, the xkrs (same diff) have u-joints and a jurid coupling.

 

There seems to be an element of luck with these diffs, have no experience with different housings/gearings.

But you could also consider shot peening the original one for higher strength, than all you need is a very experienced diff builder that takes its time to set the pre-loads perfect.

Don’t understand your ex Whitley chum either, the xkrs (same diff) have u-joints and a jurid coupling.

 

There is the Quaife option - it's not cheap, but certainly an answer. Avos' friend Tom at TL Jaguar can get them.
The Quaife unit is an Automatic Torque Biasing diff (ATB), I think the last time I checked it was around £1000.
It's something that was produced because Jag owners lobbied Independent specialists about just this problem here in the UK.
Why Jaguar did this, well you hit the nail on the head, all down to cost. When every car before the X308 was supplied with an LSD, it makes my blood boil. Having a performance car and having the electronics interfere every time I think about giving the car it's head, it's the one big downer about it.
Paramount Performance Ltd - Jaguar XJ8 and XJR Ltd Slip Differential

TL Jaguar | Jaguar Servicing Surrey Now Tom is a great guy to deal with, I spent over an hour on the phone with him talking all things Jaguar, and I only wanted to kno the cost of the diff, we certainly covered a lot of other things too, certainly someone to talk to about the simple conversion.
LSDiff on XK8/R's and XJ8/R's are GO
Norman is one of Avos for want of a better word, client's....... within this thread I think we have some very useful members all wanting the same thing, a limited slip diff, and to loose the trac button sometimes!

 

Thanks for the suggestions guys.
I never considered shot peening the gears. It's not a suprise that there's an element of luck involved: when designing any engineering component there are tolerances and processes that effect the 'probabalistic design'. For instance- if you have a crank design with a process during manufacture that involves welding with such variability that this process can lead to survival or failure- this needs to be taken into account during the probablistic design. So when you have a certain batch size- the chances are that so many will fail under the usual duty cycle. A good design absoutely minimises this number and adds a certain safety factor. This 14 HU design had very little safety factor. Many things could be said about the previous Jaguars- in terms of dependability but the diffs were pretty much indestructable with good safety factors. With these Jags- The other niggly issues have all but been solved but the Diff should have had a higher safety factor during the design stage.

Sean B- I knew about the quaife LSD insert but knowing this low safety factor 14 HU has a sub par crown wheel and pinion really winds me up.
What I've found so far is it's likely that the Dana 44 gear set fits the older 15 Hu, but the carrier holes where the crown wheel bolts on will have to be made larger. It's also likely I'll need a spicer tool to deal with the mating to the propellor shaft.

Jaguar Differential Build
like this:
"You will now have a 26 spline input shaft. You cannot use the Jaguar flange. Your local 4-Wheeler supply will have the Chevy yoke and U-bolts you'll need! Spicer #2-4-8091X"

Or this

REAR END SERVICE FOR CLASSIC JAGUARS

"The Dana Spicer part number for the new 26 spline companion flange, which replaces the old 10 spline flange perfectly, is:
DANA Spicer 2 - 1 - 2391"


I'll bet something similar is availiable- if indeed the mating of the new gear set to to the flange is a problem.
I know the old 15 HU diff will fit with the correct offset plate at the front. I'll let you know. One thing is certain- I don't want that weakly design sub par 14 HU anywhere near my car. I know the names of the guys involved- one has retired now and I feel like shooting them an email- but what's the point?

 

Looks like there could be another option to the $2k TCU reprogramming.

https://www.jaguarforums.com/forum/x...t-price-59907/

 

Phoned up B and G Chrysler who reflash the TCM for the NAG-1 Mercedes gearbox for only $400. I asked if they'd be able to reflash the Mercedes unit in the Jag and they were very uncooperative. I told him my back ground and asked what reprogramming software they used- seeing as they woulnd't help me. Again- no help or coorperation. I then phoned up my contact at Unichip and he said that they werent in the business of tuning TCMs but the signal could possibly be manipulated at the ECM end but related that this would take quite a bit of research. The other issue of course, is that I don't really have any interest in making this vehicle lower geared. If anything I'd make it taller geared.

I think it really is possible to get the Dana 44 ring and pinion at the correct 3.07 ratio installed into the 15 HU diff- but it's not straight forward and would require a competent and innovative rear end builder.

For now I'm withdrawing the Jag and retiring it back home, as I have too much on. I'm putting the effort into getting my Ram on the road and the Challenger 6 speed project. I'll continue to research this diff issue but ultimately I want the 15 HU differential and want nothing to do with the 14 HU. Infact we should christen the 14 HU diff the "Ball and Browett-cluster ****" after the two engineers who allowed it to be this way!

 

I sent this email to a former colleague at Jag- somewhat to rib him. He managed to rise through the ranks and become a part of senior management but he does take himself somewhat seriously sometimes. He had absolutely NOTHING to do with the Diff-as he, like me, is from powertrain- so its more of a joke/jab really. He is now in charge of vehicle so he'll have some visibility over the driveline in the future. He won't respond- I know it!
He certainly won't like the salary(for England) comment because engineers out there are paid absolutely peanuts!
---------------------------------
XXXX,
Can you stop being proud of your self and your company car and your high (for England) salary and stop being a Leamington Trendy for a moment and sort out Jaguars crappy reliability and dependability please?
My XJRs diff failed last night and according to my records it’s already had a diff change in 2006. I’d heard about this and heard it happens to S types as well as the X350s and X351s!
Jaguar used to have an enviable reputation for making indestructible rear ends- with the old 4HU and 15 HU rear ends in the XJ40s and early X300s. That’s why they’re used by drag racers over here. With the X308 they’d all but sorted a lot of the electrical problems but instead Peter Ball and Roy Browett skimped out on the rear end. At least with an X308 I can retro fit a rear end from an older XJ that’s also a lot stronger.

With the newest cars, they’re not only f.ugly and conformist looking, don’t offer a manual but they’re also below par on reliability! Come on- you can’t blame Ford any longer!
-------------------------------

 

Crossed the ravine on the walk bridge and tossed the the firebomb behind you!!!!!!!!!!!!

I guess you can never go back!!!

WOW

bob gauff

 

So, who is responsible for the poor excuse for upper cam chain tensioners then? Wouldn't that be the powertrain group?

There have been far more tensioner failures than differential failures. At least the differentials are not on the "must replace immediately upon purchase" list.

Decamping now.

 

HI,Count, i read your posts, on Jag rearends.
when i was building up my 1978 XJS rear,it had 3.07 ratio powerlok, i opted for a 3.73 ratio, went to my local(florida) rear end shop with it all apart,he measured parts,ring &pinion, and said to my surprise, Oh this stuff is from a JEEP, went back room and came back with 3.73 gears.

while i had it apart, i examined the inside of powerlok, had light scores on flat plates(BUT memory to myself) darn that looks like early Corvette Positraction parts.

as luck has it, had and old posi unit under the bench for yrs, around a 59-61yr corvette, take apart and it has the updated BELLVILLE spring plates,thinner but added one more plate.

well it added more bias to the unit, uses GM posi lube, and locks real easy on corner acceleration.

OK that done, Jeep pinion shaft used a chevy yoke and u-bolts , had made an all Aluminum single piece drivshaft, front fits a 700R4 built trans with overdrive, been that way since 1995.

no probs, helps to be an old american hotrodder.

 

Ronbros: That's exactly right! The Jeep To my knowledge uses Dana44 ring and pinion just like the XJS.
But even with the later diffs that were made by GKN it is possible to use a Dana44 crown wheel and pinion. Im glad about this because of the hot rod connection there is alot more potential to use LSDs like Auburn units and carriers which will be cheaper due to the volumes involved

 

These are the guys responsible for the chain design of the Jaguar V8

Tsubakimoto Chain Co. - industrial roller chain, conveyor chain, power transmission components & materials handling systems

They're called 'silent chains' and their pitch is such that they produce very little whining. You could learn from their example.

 

and to add to the Count, the plastic articles where designed by SACHS Eng Group, wait for it, FRANCE.....say's it all.....

 

Count:

Isn't the chain design as used on the primary for MY '02 x-308 what is commonly called a "silent chain". It is also referred to as a "Morse chain". I believe the common name for the roller chain on the earlier xj-8 is "bicycle chain".

And, sir, I do not care who designed the chains on the AJ-26 or the early AJ 27s, they are still a major flaw in an otherwise apparently pretty damned good engine. Thats not whining, just facts.

 

@ Sparky - It isn't the chains.....it's the tensioners. The later version, the morse, is designed to be quiet, not address the tensioners - I do agree that 3 stabs at getting them right is poor form, but that's down to the oem subcontractor, Sachs.

http://www.sachs-engineering.com/

drop them a mail....

 

Outsourcing doesn’t automatically exempt you from responsibility imho; I mean Jaguar did know they were French right?

 

The French almost bought Jaguar. Had that happened- would we have seen a rebirth of the vel Satis- with a Jaguar grill grafted on?

 

The X300 XJ6/XJR/XJ12 do not have a speed sensor that would pick up the pinion/transmission output rotational speed - like most older Jaguars and other cars. Instead they use the ABS sensors (I think left rear sensor) to get the vehicle speed. This means that changing differential ratios (but not tire size) does not affect the indicated speed. (Even the XJ40s used an exciter wheel/pickup combo on the OUTPUT shafts, not the transmission/pinion).
So, if the X308 also uses one of the ABS sensors, then changing the differential ration should not be an issue.
So the only problem I could see is that the ECU/PCM would see a mismatch between road speed and engine RPMs for each gear. On the X300 (and likely XJ40) is does not matter, but you might want to research this for the X308.