I am in for check up just before warranty expiration on my 2010 SC. I finally got them to hear the slight clunk I have had for some time on mid speed deceleration and acceleration transitions (seems like a tiny bit of excess lash in the drive shaft u joints or something) very subtle but annoying.

Anyway, they called and said they ordered a new e-diff actuator motor....that it was thought to be the issue. I wanted to see a diagram of what and where it is. Googling product nothing. 2010 and up XFR and SC have same drivetrain so either would be useful.

 

It hangs off the back of the diff to the right side if my memory serves correctly, maybe I'm thinking of BMW s version. The electronic actuator controls the clutch pack pressure internally.

As for the clunk is that possibly the infamous ZF transmission thump as you approach a stop? Or s it driveline lash?

 

No, I know the ZF thump. This is a clunk (usually felt but sometimes heard) when you are transitioning from power application driveline load to engine braking driveline load or vice versa. There is a transition in any vehicle but in mine if it is gradual enough you hear and feel this very slight clunk. It needs to be at speeds, RPMs and gear combos where things are loafing a bit to really feel it. Don't know if they are on the right track but last time it was in (10k ago) they re-set the transmission control and I knew it would do nothing...and it didn't. This is a mechanical issue. With the tech this morning on a test drive he definitely heard it. I suggested he look at slack out of spec in the universals etc. The adviser said they had ordered this part late in the day. We'll see...at the very least I get that new part under warranty and they can look at other elements.

I'm pretty sure its to the rear so engine tail and transmission are unlikely (always has shifted flawlessly) That leaves universals and diff and I guess axles. This is a very subtle thing that only I notice but if I can get it eliminated coming off warranty then I will love the car even more.

 

If you at also having trouble with the diff then I'd get the pinion lash checked. This is just the free play in the diff input shaft back and forth and should be undetectable basically. The pinion is shimmed on assembly of the diff so as to eliminate this lash. Unusual wear in the gear set can give this symptom. Jaguar had a run of bad diffs early on, though not the ediff.

 

I agree thats what it seems like but with the car on the hoist that would be very quickly obvious I would think...if you grabbed the drive shaft and cranked it one way then the other even by hand you would feel play if there was some. Dealer tech's have surprised me before so I guess I shouldn't count on the obvious being found. Just hard to picture them choosing to replace the edif actuator (sounds spendy) but the alternative I suppose is the diff itself coming out for rebuild or replacement.

 

Correct, But I had my E-Diff motor changed as the problem I was having was a shutter feeling when I would make a full left or right turn from a stop.
And when and if it fails the shutter will be gone but so will that posi effect.
I would for another culprit like others have mentioned.

 

Update

Was in for the final check up prior to warranty expiration. They replaced the e-diff actuator as they said it was "locking up". As suspected this didn't take the problem away. After being away for a week of travel I got over there this morning and made sure the tech understood exactly what I meant during our drive. Coasting along at 40-50kph with slack int he driveline and lightly pushing accelerator and letting it off (tiny bit both ways to put tension in the system) and you get an audible but very light clunk noise.

I left it with them and they called and said they are requesting approval to replace the diff. Have to take a fluid sample. In that it is an independent rear there is nowhere else to look....no u joints etc in the drive shaft...straight from output to diff. I guess its possible that one of the CV joints on the axles could be bad but I'll take a new diff if they can do it especially as I come off warranty. I noticed this noise on occasion when it it became my car at 30k miles so I think its a lash issue that has been there from the start.

 

The "prop" shaft as the British call it has at least two Hooke's joints and maybe three. The only solid prop shaft setup I know of requires a rigid torque tube locking the transmission tail shaft housing to the differential pinion housing with a solid shaft within riding in a series of bearings. Another torque tube type solidly connects the flywheel bell housing to the clutch housing on a rear mounted transaxle. Ferrari pioneered this layout with their 275.

No car uses an open driveshaft without universal joints at each end, the vibration would be intense and the whole shebang would self destruct.

Isolating drivetrain lash from the transmission tail shaft to the drive wheel is not rocket science. However, if you are to get a brand new ediff under warranty don't whisper a word of this until after you get your new diff and the problem remains!

Jaguar uses carbon fibre prop shafts known for vibration issues but the universal joints are robust and reliable.

 

I asked him exactly that....does the shaft have universals? He said no...It occurred on me that with the independent rear that the pumpkin is fixed in place and not need for one and I didn't question him further. I think you are quite right obviously you need isolation for flex of engine on mounts etc. and vibration. I asked him if when it was last in did they even just grab the drive shaft and see if there was play even under the human hand on rotation? He said yes and there was none. Guess we will see.

 

Another update. They are replacing the diff. Part coming tomorrow. Rover LR2 loaner. Why would anyone buy one? No offense to anyone who has.

 

The LR2 is basically a warmed over Ford Mondeo. The Freelander was based on the same platform as the Jaguar X Type. The fancy and hit selling Evoque is the same car. The new baby Jaguar is very likely to be based on this architecture, or its next gen successor.

 

I would say very lightly warmed over. At least the Evoque has a bit of style. I see very few redeeming qualities in the LR2.

 

Amazing what a nice little black dress can do for a plain Jane. !

Until you take her out again in the daytime. !

 

So....they replaced the diff. (love to know the cost on that) I have yet to completely conclude but it is better but still there. In that clunk transition zone there is clearly a more buffered feeling but I think I can still evoke the noise. I say "think" because after a long week I was just trying to get from dealer to home with minimum fuss. I will see what my weekend shuttling about shows.

The question is whether I persist in chasing this.

The service has been impeccable.