Having just extracted the differential oil plug on my 2004 X100 convertible I have discovered that someone has been there before me and has hacked up the plug's ½" drive recess almost beyond recognition. At least that provides the answer to why it was so difficult to engage the tool.
It seems to me that a replacement plug with an external drive purchase would make this process much less complicated. Perhaps something like in the picture below.
Is there such a replacement part in the aftermarket?
If not, is there a source for the OEM type of plug?

 

Hi Brian,

I'm not sure if there's enough clearence as my pit is busy with another car presently, but if there's room, you could modify Gus Glinka's solution by cutting a one inch piece of 1/2" key stock and tack weld it
into the damaged plug.

Best, Rick

 

Rick, thanks for that. I had considered doing that, but after using a Square Drive Socket Cap (pic below), and having to flip the open end wrench on each and every flat, I cannot imagine how one would get enough turn to make progress with only 4 flats...... This might be a convertible only issue due to the extra bracing in that area.
Indeed, I might end up brazing this tool into the plug.

 

On another note:
Does anyone know precisely what is the thread specification of the diff plug?

 

I can’t answer your question, but from experience I can verify that the coupe diff plug is not that hard to access. I use a 1/2” square drop in that has a 3/4” hex head. I use a 3/4” open end / box
end wrench to turn it.

Amazon has them :

https://a.co/d/h3STlvG

i think the convertibles are a different story and are harder to get to.

Z

PS: SNG BARRATT has the OEM part for $20:






o

 

John - To the garage on youtube - cut an access hole in the trunk & used a socket extension & ratchet on his.

 

not sure what the issue was with using the square drive socket cap. It took me about 2-3 minutes to remove the plug with the 1/2” square drive / 3/4” cap tool. Is that an excessively long time ?

Z

 

Apparently that works a treat on the 4.0 coupe. The convertible has a second sheetmetal brace between the trunk and the differential frame. Even worse on the 4.2 convertible is that one of the evap carbon canisters and the operating servo are located on that sheet metal brace, right where the hole would be located. As well, the battery connector panel in the trunk is also mounted on the surface where the hole would be drilled.
No expectation of easy projects on this car! 🤣

 

I would suspect that your car is a coupe. They have much easier access back there.
This picture shows the extra support sheet metal bracket between the trunk and the differential frame, as well as the 2 cross-frame supports which are all specific to the convertible.

 

I do mention that in my sig, and my post does also say my experience is with the coupes, and that convertibles are more difficult.

Every model variation has trade offs, with some items being easier and some being more tedious. Such is life, no ?

Z

 

The problem is getting it into the hole square to to thread. On mine I had to turn off a few threads so that it dropped in square and engaged the threads without going crossed . If the diff case threads are damaged then coat with araldite and make sure the breather is clear.

 

Although not all convertibles have the second sheet-metal brace. Mine doesn't and John's didn't because we both have early models. Once you cut the 50mm hole in the boot panel, you have direct access to the diff plug. Just make sure you drill as high as possible on the side-panel or you will have John's issue where a suspension rod is in the way.

Richard

 

Drilling that hole would entail moving too many components mounted to that sheet metal on my '04 convertible.
I did get mine out. Replacing it may be another story.

 

That's a brilliant idea! I have a lathe and can easily turn off a few threads to create a threadless pilot.
I will definitely coat the threads with a never-set thread sealer like Yamabond 3.
s
Still, I would like to replace the OEM plug with an O-ring seal type.

 

The thread in the diff might be tapered or parallel, I don't know. If it's parallel then you could rig up some kind of O-ring alternative but if it's tapered then that I suspect that it will be very difficult to get a satisfactory seal.

Richard

 

I don’t know about other years, but if I recall correctly, on my 2002 the plug is tapered.

in any case, is anyone having an issue with the plug leaking? Mine is clean (surprise !).

if leaking is an issue, or wanting a preemptive fix, then I’d use Hylomar. Nothing better at gas or oil resistance.

Z

 

Indeed, the plug is tapered. However, BSPT plugs can have tapered or parallel sockets, although usually parallel, I believe. The only way to check this is situ with such poor access is probably to buy a parallel plug with a flanged head and see if it screws right in. If it does, you could put an O-ring or similar on it if that was one's preference.

Richard

 

Thank you for the confirmation of the BSPT thread on this plug. I have been able to locate a local source and have ordered one with an external hex head. This will facilitate the next event of this process, should it ever happen.


I might have guessed that Mr. Whitworth was involved, having a 1972 Norton Commando in restoration in my garage! 🤪

 

I was working at a Triumph motorcycle dealership when your Commando was new, and the two previous years, 1970 and 1971, as well. (Triumph of Oklahoma City).

At that time Triumph was transitioning to metric from British Std. So we had a mix of fasteners: British, American, and metric fasteners; all on the same bike.

it made for an interesting day.

Z

 

I bought this one new from a Calgary dealership in 1972. The factory choice of fasteners definitely broadened my tool collection at the time. 🤪
That helped with my subsequent ownership of a '68 E-type and a '86 Vanden Plas. I haven't had to break out the Whitworth wrenches for the XK8 yet.....