Update:

While Wayne and I certainly had another great time together at his home shop today, my wife's 2006 XK8 convertible indeed had way too much bracing and too many metal plates preventing Wayne from even getting a tool up and onto the rear differential drain/fill plug. There is no room at all from any angle, and he tried every approachable angle while we were underneath the car. The entire rear suspension and possibly some of the exhaust system needs to be dropped in order to get to the differential drain/fill plug. I was not willing to commit to that drastic action at this time because we may very well have broken or damaged some of the 14-year-old components up in those tight spaces that we would have no replacements in hand for....

The good news is that there were no differential fluid leaks and the general area still looks to be in great shape after nearly 120,000 miles. So we decided to leave well enough alone for now. The 4.0 rear differentials are doable without major disassembly but that is certainly not the case for these 4.2 rear differentials....

We were determined not to let a gorgeous autumn day get by us so we mixed up a bucket of chemicals, grabbed some scrub brushes and a garden hose, and washed the entire outside front elevation of Wayne's three-bay home shop from top to bottom. All of the hot-and-humid summer mildew is now gone and the garage doors along with the vinyl siding are now sparkling clean again. Then we headed over to the local BBQ joint for a great lunch....

If anyone figures out a way to get to the drain/fill plug on these 4.2 differentials without dropping the rear suspension, please share the magic with us. I do not believe it is possible....

 

If I could get my hands on a 4.2 I would look at it.

 

Geez! Bad luck there. These cars throw all sorts of curve *****. If Jon and Wayne can’t do this job, the rest of us don’t stand a chance. LOL!

It’s on my to do list but haven’t summoned up the courage yet. Car running well so far, so I’m delaying the job as I can’t figure out a way.... yet!

FWIW Jon89’s problem is probably the reason there’s that Youtube video of someone coring a hole through the rear trunk wall to access the filler hole.

 

David, first off on my best effort or smaller hands and contorted position, I could get one finger in the fill/drain hole where the 1/2 inch insert would go.
Drilling a hole for access is pretty much out of the equation. There is a extra plate between the rear and the trunk firewall, plus the fact there is a 3/4 inch hose that runs the length of the trunk in that area from the evaporation canister with a little extra plastic valve of some sort directly behind in line fill/drain on the trunk side of the extra plate. Any drilling at the angle required would put you right through the hose coming out and across.
The sway bar could be removed, but that would only give you a better shot a the rear bracing which needs to be removed and slide to the drivers side. After thinking it over i believe just getting it out of the passenger side area will give you a small access area. The bracket that holds that brace is still going to be the challenge, as it covers the plug about a inch and half away. Under the rear is a plate that covers the entire rear end, so drilling a drain hole with plug there is out of the question, major effort to get too it.
Your best plan would be to plan on dropping the complete system and replace the shocks at the same time, kind of a double task or while you are in there.
With 120,000 on this car, i could not see any major wear areas or bushings that appear to need replaced.
A leak would have a changed the whole approach.
So now you know the rest of the story of why no Utube on this.
Still had a good time and got the last nice day for a week or so. Thanks to Jon we are still full of BBQ.

 

David,

You should be able to get to your 4.0 differential drain/fill plug with a short piece of 1/2-inch square stock and a long thin wrench. Read the description and look at the photos that Gus posted when he did his car several years ago. Granted, that job is a definite pain in the *** but at least it is doable. Not so for these 4.2 cars. If we ever need to drop the rear suspension on my wife's car, we will do fresh differential gear oil at that time. We did her rear shocks a little over five years ago, they are still in great shape, so this rear differential job can wait....

 

Jon, I said near the beginning of this thread that a short piece of 1/2" square stock will fit the hole, and it can then be turned with a 14mm 12 point wrench, even better, ratchet wrench. My hands aren't small, but I managed to get the square in the hole with the help of a screwdriver.

 

That was not the case for us. I wonder if my wife's car's undercarriage in the rear differential area is somehow different from yours. Is your 4.2 car a convertible or a coupe?

Wayne could get his hand in there far enough to touch the drain/fill plug with one finger, but there was absolutely no way to slide the piece of 1/2-inch square stock into the plug, much less get a wrench up in there....

Please come to Wayne's home shop in Spencer and show us how you did it. You name the date and time and I will be there with my wife's car....

 

John89, this can be done in situ on a 4.2 convertible, RJ237 is correct, it has been documented many times here in the forum.

I did this back in 2012, here is the thread showing how, its listed in the stickies at the top of the forum.

https://www.jaguarforums.com/forum/x...iff-oil-71492/

 

If you visit OC Md / Berlin Md for the holidays or whenever I can get it on the lift and see what you have going on. Just let me know by email.

 

A question for those of you who successfully completed this job on a 4.2 convertible:

Assuming the drain/fill plug location is at the center of the face of a clock, at what position did you insert your wrench to successfully loosen and later tighten that piece of 1/2-inch square stock after you managed to get the square stock piece into the plug? 3 o'clock? 9 o'clock? I was right there holding the flashlight when Wayne was maneuvering his hand all around the rear differential area during his multiple attempts to find a way in for the wrench. We spent at least 30 minutes underneath the car and I never saw anything close to a reasonable pathway for the wrench....

 

I can't remember what position the wrench was in as I did it so long ago, but from this pic I took at the time it sort of looks like it was vertical, upwards.

 

My wife's car has a large metal structural plate directly underneath the drain/fill plug area of the rear differential. No way to run a wrench straight up from the 6 o'clock position....

 

It's not 6 o'clock, its 12 o'clock, look at the picture, you can just see the shaft of the wrench at the top edge.

I really don't think your car is a one off.

 

RD, I see you have the wrench inserted on the vertical and believe it or not, that was the only position I could even see the plug.
I certainly applaud your success, but even with a ratcheting wrench I was not going to risk not being able to get the plug back in with Jon over a 100 miles from home. Not sure I could have got a paint stick in there. The bracket you are between does look a bit different, but can't imagine that was changed.
I have gone over it in my mine several times, even after looking at your pictures and am in amazement of your and others being able to do this. May be time for me to hang up the tools for display.

 

Wayne,

Maybe my eyes are playing tricks on me but from RaceDiagnostic's photo above, it sure looks like he has more open space around his drain/fill plug than we had yesterday. Perhaps the bracket and plate design was indeed changed between the 2003 models and the final batch to roll off the line in May 2005. Jan's car was indeed part of that final batch....

 

Jon, as the consensus says it can be done, on your next trip for what ever reason, it will be back in the air and take a few pictures if nothing else. Something is different, as I tried over the top and the sway bar pretty much covered that area up. I think I mentioned if we take that off, we might have a chance. I'll study RD's link a bit more to be prepared for something I missed this time.

 

No worries, Wayne. Jan's XK8 is behaving perfectly now (we drove it to lunch this afternoon) and I am not worried one bit about the differential fluid. If we can find a relatively quick way to gain access to that drain/fill plug, we can service it at our convenience. If not, so be it....

What is important now is our rendezvous at Stamey's in Greensboro in mid-December to celebrate the holidays with the wives. I am greatly looking forward to it....

Enjoy your weekend....

 

RD and others, I do see how it can be done now.
One question, just how square is the corners of the plug?
The one I have is square stock, so the corners are very square and I see you have yours rounded off. Sure would hate to get that far and not be able to insert the darn plug. I ask, because mine uses a 15MM ratchet wrench for a snug fit on the plug and a little contact glue should hold it in place but not so much as not being able to separate it.
Thanks for all the advise and pictures, don't know why we couldn't find or maybe it was not understand the information already here before we started the adventure.
No way would I have believed it was that constricted in that area.
Again, next time we will get the little bugger.

 

Hey Guys, I used a piece of square tubing, which I had to grind down a little to get it in. I believe it was over 1/2". It's possible I had the ratchet wrench positioned over the hole and slid the tubing in, but I don't think that would matter. The wrench was somewhere around 3 o'clock and motion limited thus the ratchet wrench. My car is also a 05 build, carbon fiber edition.
I was just up in Wake Forest near the end of Sept. but won't be back until the same time next year.

 

RJ,

I live less than 30 minutes from Wake Forest. Next time you are up this way, let me know and we will meet up for lunch....