X152 Folks,
How many V8 owners have had issues with their rear differential? What were the issues?
I have developed rebuild options for the V6 series rear diffs: f-type-x152-72/v6-base-lsd-swap

And I will now look into the V8 eDiffs… see what goes wrong and how to best repair them.
Look here for a tear down of an eDiff, and links to new YouTube videos on how to fix these units.

 

Awesome. Thank you.

 

Looking forward to the tear down and the possible repair/upgrade option!

Although not wide spread but the oem unit are prone to overheating under load and premature failure due to clogged breather port.

 

@Ray Ray
Thanks for posting your thoughts on V8 eDiff’s overheating due to vent port clogging.
I have been inside a bunch of V6 rear diff units and have not found any clogging in the vent port… but the V8 does have the electronically controlled diff which could exacerbate the issue of generating heat and fouling of the oil and vent tube.
But so far, my engineering mind says that vent port clogging is a result of overheating, not vice versa.
Thoughts?

Notes so far:
The V8 has about 50% more engine torque than the V6
The V8 diffs tend to have 25% lower gear ratios than the V6 diffs (2.56 vs 3.31)
the V8 eDiff carries 60% more gear lubricant than the V6 LSD. (1.2 Lit vs. 0.75 Lit)
the V6 friction LSD has four clutches, while the V8 eDiff has 10 clutches…
The V6 diff clutches are similar to the V8 diff clutches (same Carbon Fiber friction pads)
The V6 diff friction material (carbon fiber) falls off the clutch discs (stainless steel)
The V8 diff units tend to over heat, which may be related to the 12V control motor seizing or partially engaging the clutch pack

 

Super interested in hearing more about this - especially your theories on why these diffs overheat.

 

@HermanWiegman i don’t think i know enough about differentials to comment on which came first, but i first saw the issue here
or somewhere on the forum, it’s actually clogged breather port blowing out the pinion seal causing slow leak of fluid and eventually kills the diff if unaddressed.

Overheating and sludge build up might be a different issue altogether but i wouldn’t be surprised if one accelerates the others and Vice Versa.

Overheating have been documented on the forum quite frequently, i might have encountered it once when i first got the R back in 2019, open parking lot and fresh coat of snow, guess what i did, no warning message but the car refused to spin after some slides with traction fully off.

i have also attended 2 rookie track days and did not encounter any issue with the diff, but i drove like a rookie so it’s not saying a lot.

 

@Ray Ray
Thanks for the link to the Skrrt garage video. It had been several months since I last saw one of his videos.
There are two take-aways for me:
1) clogging of the vent tube may be an issue on eDiffs (I know it is not on V6 open diffs, and V6S LSD’s issue)
2) a clogged vent can result in elevated pressures internal to the diff, ending in pinion or axle half seal failure.
Note: the half shaft seals are situated above the natural oil level, so they will not normally leak much oil.
The lower side of the pinion seal is right at the natural oil level, and it has constant oil spray from the rotation of the ring gear, so much more likely to leak.

I have not yet identified a source of eDiff vent clogging… but it would appear to be worn friction material + oil which collects in all corners of the diff.

I will post some photos of what I found in my used (100 kmile) Jag XJL eDiff… and perhaps a YT video.

 

Here is an update of the eDiff teardown from a 2016 Jag XJL 5 liter car.

Yes, there was "crud" or grime inside the unit, even though this used example was in pretty nice shape.
And yes, some of this grime ended up in the breather tube, which can cause oil seals to fail.
The 12V motor, which drives the engagement of the clutch discs, was not high quality, and is a possible failure item.
The generation of heat is from normal operation of the eDiff, and can be exacerbated by a faulty 12V motor or aggressive driving.

The owner will become aware of eDiff issues by:
a) diff oil drippings on the floor of the garage.
b) the dash warning will indicate "DSC Not Available"

The preventative maintenance is to
1) refresh the diff oil on regular basis to avoid grime build up.
2) clean out the breather tube (see Skrrrt Garage video above in a previous post)

I am having upgraded clutch discs made at RacingDiffs (similar to the V6 LSD disc kit),

Here is the summary video on my Onca Engineering You Tube channel.

 

Very detailed and informative, video saved for future reference!

the unit looks good having 100k miles on it, wonder if it ever had the fluid changed or serviced, I’d assume an xjl is usually being driven normally and the owners wouldn’t touch it unless something is actually off.


Does it being electronically controlled pose a challenge for change/upgrade/replacement compared to the v6 diff? Say you want to change the ratio or change it to a mechanical unit.

 

RayRay,
Yes, I think this unit (from an Jag XJL) was not stressed much, and did not spend much time in the "partial engagement zone"
So very little clutch wear, and very little grime/crud.

1) F-Type V8's who want a simpler rear diff, but keep the 2.56:1 gear ratio:
I have seen normal (non eDiff) open rear differentials with the 2.56 gear ratio.
(see eBay for Jag XJ, XJL, XF sedans with 3.0 liter and 2.56 rear diff ratio)
(https://www.ebay.com/itm/235536929590)
So F-Type V8's can leverage these simpler diff units (Open diff) and swap in a Quaife helical ATB or V6 S model LSD carrier.
Also the left hand side half shaft has to be exchanged from a V8 kind (special mate to the eDiff cover side), to a V6 kind (mate to the conventional cover side)

2) F-Type V8's who want to keep the eDiff, but get a different rear gear ratio:
I will take some measurements of the eDiff carrier and see if it can accommodate different crown gears
It may be possible to graft a conventional V6 diff gears and a V8 eDiff carrier together to get to different ratios.

All of the data in front of me.. let me coalesce it together.

What is your need or desire?

Drive Well, Herman

 

Nothing in specific, was more curious if the car can detect the change and throw a code or limit performance.

 

A question about the rear diff vent. What is located above it? Is it just the floor of the rear trunk (and not the gas tank)? If so, could one cut an access hole in the trunk to allow easy inspection and cleaning of the diff vent? You could seal the access hole with a panel plug. If such an access hole is possible, that makes regular inspection/cleaning of the vent pretty easy. Thoughts?

 

@Ray Ray I am not familiar with the eDiff controller. I know it is located in the rear boot / trunk area.
We know it gives a warning to the driver when the eDiff temperature sensor reads too high.
I think I read somewhere on the Forum that a faulty 12V motor also caused the controller to throw a code/warning.
And it is probable that an unplugged 12V motor would cause a warning (DSC not available).
Perhaps the car needs to have the eDiff feature disabled if one converts a V8 car to a conventional diff.

@diablo2112 The vent is on top of the diff, which is bolted to the rear sub-frame.
The vent is just below the rear floor, and not close to the fuel tanks.
See below graphic. (top down view of the F-Type subframe)
I would think that the rear trunk/boot carpets could be pulled up and an access hole/cover could be added to service the vent port.
With the exhaust pipes running under the sub frame, it is really difficult to access the vent from the bottom side.


Jaguar F-Type Rear SubFrame diff vent port location

 

When i had my pinion seal done, i requested to have the vent cleaned.

My mechanic said he will blow it out, I’m assuming that means compressed air through the drain/fill hole, which would be really clever and easy to do.

 

@Ray Ray Having the rear differential vent tube "blown out" sounds like good preventative maintenance.
Yes, one would blow the "crud" back into the differential, which is reasonable, as there is were it came from.
But it is exceedingly difficult to do this task when the rear diff and sub frame are in the car.
Having a trunk "access panel" would be a good option. Let me take a few photos of the boot/trunk of my Coupe and see what that would look like.

 

I think blowing from the fill hole will probably not put any crud back into the differential.

The fill hole should be accessible without dropping the subframe, not entirely positive on this though.

There is a hole sealed with tape in the floor pan, iirc it should be pretty close to the vent tube.

 

Reading this thread and looking at the posted videos, it seems really smart to clean out the vent BEFORE it can clog and lead to a blow out of the pinon seal. Perhaps among the most important bits of preventative maintainence we might do on our Type Rs.

I’ll do some measurements and I’m ok with cutting a hole in my subfloor to provide an inspection hole for the diff vent. I’ll take a few pics and see if I can help with providing the proper location for the hole. Sounds like a nearly painless way to solve a potential problem before it occurs.

One last comment: using compressed air to clear the vent would work, but I would be very careful not to pressurize the diff during this procedure. You could inadvertently blow out other seals if you’re not careful. Personally, I’d use a pipe cleaner or something similar and not compressed air.

 

@Ray Ray Dough!! I was stuck on the top vent port as the location for applying compressed air.
Very good idea to blow into the fill port. It is much more accessible than the top vent.
But there is still risk of popping the oil seals if the top vent port is clogged.
So would it be lower risk if compressed air was applied to the top vent port, and the fill port was open to relieve any internal pressure?

@diablo2112 Additionally having an inspection port in the cargo bay sounds like cheap insurance.
I will still take some photos and identify where I think the top vent is located (same place for V6 and V8 cars).

 

Success. After a bit of prodding and looking around to convince myself nothing important would be cut into, I used a hole saw to cut a 3.5" access panel, and had easy access to the vent plug. To locate the hole, I first marked the position of the rear axle (with tape), then translated that measurement to the floor of the trunk with a bubble level. I looked carefully at both the floor and the diagram of the vent location, and decided to drill the hole slightly to the right and in front of the axle. Note: 2 pieces of sheet metal join in this region. I tried to drill out the forward portion only, but still caught some of the lip of the rear piece. If you're doing this, I'd drill 2" closer to the front from my location, but it's not a big deal.

The vent was nearly perfectly in the middle of my hole. 3.5" was the smallest hole I could get my hand through, and from there, it was just a matter of cleaning up around the vent, then cleaning out the vent. I used a nylon tie wrap. I found no gunk at all in my vent, it looked really, really clean. Now, peace-of-mind in knowing I won't have vent issues.

To button it up, I used a couple of pieces of sound deading, and captured the piece I had drilled out in-between. Easy peasy.

To help you in locating the proper place to cut out the access hole, note the 2 pieces of tape in the photos below are centered on the centerline of the car and the rear axle. Center of tape in each case. Note again, I'm cutting just to the right of the centerline (2" to be specific) and placing the lower edge of the 3.5" hole at the seam for the 2 pieces of sheet metal. If I did it again, I'd cut the hole 2" closer to the front of the car to avoid the sheet metal seam all-together.

Here's a few pics.

 

Well done!
And a great first hole saw cut through the aluminum.
Looks like moving the center of the hole cut an inch or so further forward would help give the center bit some more room.

You could also have a cover plate made up from Aluminum from SendCutSend.
See their flange design below.