Prescott Hill

[malcolm]

Would standard diffs and LSDs BOTH click when on the limit cornering hard, or does that only apply to LSDs?

[Dave123m]

Hi Malcolm,

I would agree that the noise you heard at Prescott is unlikely to be the diff as the frequency was too high, I would hazard a guess that it is more likely to be something like the Propshaft bolts hitting the crossmember behind the gearbox?

As mentioned by others if the rubber collar on the rear gearbox mounting has perished this would probably allow enough movement to allow contact?

Also standard diff's should never make a noise like this unless the pinion or one of the crown wheel bearings is breaking up.

Due to the configuration of the IRS there is an incredible amount of load on the diff output bearings & when mine started to breakup it was only really noticeable on tight corners (mine is a Powerlok LSD) & there is often oil leakage from the damaged side which often gets onto the brake disc.

I would suggest your diff is ok but good luck locating the source of this & good to see the car being 'used'.

Regards,

Dave

[PeterCrespin]

Where is it stated that 2+2s of any series lack a Powr-Lok diff?

There are some Federal S2 with open diffs but they are fairly rare

Those that lack an LSD could be an OTS or FHC just as easily as a 2+2 AFAIK

[44DHR]

I have not heard a Jaguar "Powr-Lok" LSD make such a noise before. If you can get your inside wheel to spin under power, it is unlikely you have a LSD as the whole point of a LSD is to prevent this.
If you jack both rear wheels clear of the ground, a Thornton "Powr - Lok" as fitted in a Salisbury 4HA differential in E types, should be already locked to a certain level and this will enable both wheels to rotate in the same direction. If you can get any movement with one wheel held - or still on the ground - the clutch plates are worn or the Belleville Springs at the end of the clutch packs are broken and not maintaining the pressure to lock the diff. Under normal motoring, the clutch plates overcome the spring rates to permit slip and allow normal cornering motion with the inside wheel turning less than the outer wheel.
It is only once the inside wheel loses traction on cornering, or you apply extra power to break traction on both wheels that the clutch packs are further forced together by a cam process within the centre of the differential. The differential cross pins which mount the planetary bevel gears that rotate the driven bevel gears on each side of the differential are not fixed in the differential main case as in conventional differentials. In this form of LSD the cross pins are free to move up a ramp in the cam surface of the main differential casing and these apply a outward force to lock the clutch rings and friction plates in the two clutch packs each side of this main casing to lock the two sides to overcome the loss of traction.
All this should be smooth with no noise as the locking process is an internal cam action and provided the friction plates and clutch rings are perfectly clean with no damage, when running with the correct oil - as the LSD uses an additive - there should be no clunks or grinding noises between the plates as they move in normal operation.
It is fairly fundamental to know what differential is fitted to any car - particularly if you are going to drive it hard - as the characteristics differ greatly between a non-LSD car to one fitted with a LSD. The non-LSD car will give a margin of error as the inside wheel will just spin as traction is lost, however a LSD will lock and potentially give you a drift situation.
Regards,
Dave

[John_Mann]

[quote="malcolm"]Here's me doing the climb. Can anyone tell me what the horrible graunching noises are when I go round the first hairpin? (Not the ones my wife is making). Under very heavy steering.
/quote]
Hi Malcolm,

Had the same issue with my S3 when going through a tight corner or round about, particularly when it was warm. This is attributed to the clutch plates grabbing in the Power Lock diff. Assuming you have a power lock fitted, I'd say that is highly likely the problem. In my case, i suspected that the previous owner didn't use the appropriate PL diff oil or additive that the PL diff requires. As such, I dumped the oil that was in mine and replaced it with Penrite 85W/140 (specifically formulated for LSD/PL diffs).

The result was the clicking has stopped and it is now working as it should. With the correct oil or additive in the PL diffs, the clutch packs shouldn't grab to that extent when going around a corner. These diffs originally used a whale oil additive, but that is a bit taboo now a days.

And no, it is not normal for that clicking to occur. Should be silent and smooth.

Nice video by the way.

Cheers;

[malcolm]

Thanks John, and all others. I obviously need to do a bit more investigating. I don't have a ramp, but the car is going in to have a handbrake job done later this week, so I'll get them to pop it on a ramp and at least identify the diff type, and look for any obvious problems. Also, look at the gearbox mounting rubber.

[mgcjag]

Hi Malcom....this is a tag from one of the bolts on the diff....if a lsd it would also have PL or PWL stamped in..cant remember which.....the 43/14 is 43÷14=3.07 ratio

[malcolm]

Thanks Steve, good guide.

[44DHR]

Don't just go by what the tags say as often these are missing.
For a Powr-lok, the tag if present, will say "B P-L" or "P-L".
It is very easy to see if it is a LSD differential by turning the wheels when both are off the ground.
Regards,
Dave

[malcolm]

Thanks Dave, I'll do that

[richard btype]

Any further images please of the 3.4 etype?

[Hugo]

[quote="cactusman"]

Lovely to see vandal was there. He can scribble on my car any time....

I am embarassed to show my ignorance, but who is he?

[mgcjag]

Hi Hugo.... https://en.m.wikipedia.org/wiki/Norman_Dewis

[Hugo]

Thank you - I thought it might be - but he looks like a Texan in that photograph!

[chrisfell]

Thank you - I thought it might be - but he looks like a Texan in that photograph!

What you can't see is the Cuban heeled boots he was wearing. Mr Dewis always appears at official functions such as this (I understand he is an unofficial ambassador for Jaguar) with a boot lace tie, his favoured jacket and the aforementioned boots.

[John_Mann]

Don't just go by what the tags say as often these are missing.
For a Powr-lok, the tag if present, will say "B P-L" or "P-L".
It is very easy to see if it is a LSD differential by turning the wheels when both are off the ground.
Regards,
Dave

Not all PL diffs have the "P-L" designation on the tag, so that is not a reliable way to confirm. Mine is a 3.3 ratio PL diff, as per the pictured tag.

[44DHR]

John,
There should be two tags on Powr-Lok diff, one showing the Crownwheel to Pinion ratio, (as you show) and the other one a separate tag of "P-L" to show it is a LSD diff.
As I said in my quoted comment "if the tag is present", because these could be missing - as in your case - potentially after work on the diff.
I note you have a Series 3 E type, but the use of two tags was not discontinued at a certain point as the later Jaguar XJS diffs that I have fitted into Series 1 US spec E Types still have the two tags, with one showing the "P-L", but interestingly the diff ratio now is shown on these later diffs as a single number such as "3 54" on the tag for a 1:3.54 ratio.
Regards,
Dave

[John_Mann]

Thanks for the clarification Dave. Always learning something new with my E! Guess the separate tag has probably been left off, in my case.

Cheers;

[Bob.]

For info extract from Powr-Lok manual re LSDs chattering -

[chrisfell]

Any further images please of the 3.4 etype?

Richard, I'm away from my laptop at the moment warming myself in 30 degree Caribbean sunshine. When I get back I'll put together a thread on this car and it's history, most of which is well known, plus some stuff from my own history files. I've known this car and it's current owner for many years.