The 'E' Type Forum

The thread on the Filler/level plug and the Drain plug on a Jaguar Independent 4HA Differential is 3/4" BSPT, (British Standard Pipe Taper).

Hopefully, this post is a definitive article on the thread type following the previous Technical post titled removing diff filler/level plug which has attracted over 2,100 views to date and prompted a discussion on the type of thread used on the plug. To avoid people having to trawl through that post and get a simple answer to the thread used, I have created this new post.

The previous thread, (no pun intended!), highlighted the issue of finding a suitable tool to fit the male square drive on the standard differential plug. Should anyone wish to change this plug, particularly the filler/level plug - to a different form of drive, such as an Allen key entry or Hexagonal head or just get a better more accurate square drive, they now have the thread size to use. In my research, I have looked at several other car forums who use the Salisbury 4HA differential and this question has also been raised there.

It has been an interesting (!!) journey and I have found a definitive catalogue in New Zealand on most Sump and Differential Drain Plugs and washers used worldwide. I draw your attention to pages 11 listing the Pipe Plug 3/4 -14 PTF DP 3003 and Page 24 showing the details and photo :- http://www.acl.co.nz/wp-content/uploads ... alogue.pdf

I also received the following in an e-mail from S.N.G. Barratt. "The threads in the differential casing of these Salisbury axles are 3/4 BSP, the standard iron square drive plug (3823 which we supersede to the later 607172J) is 3/4 X 14 BSPT (tapered thread). It is interesting that the female plug used in XJS and some later differentials (JLM632) is also listed as 3/4 BSP. Unfortunately, we supersede this part also to 607172J so I cannot check to see if JLM632 is also a tapered thread "

Examples of Plug designs :-

A= Standard Jaguar Black Iron plug, (removed from spare differential), around £3.00. Note the drive is not exactly square, but more a diamond shape which could be giving the issues on finding a suitable tool to undo it, as highlighted in the previously mentioned post.
B= 3/4" BSPF Nickel plated Allen key drive plug with 10mm Allen Key entry from eBay at £4.07. There is even a larger 17mm Allen key drive plug in alloy on Ebay at £7 as Subaru use this thread in their differential (albeit Japanese JIS Tapered Pipe Thread, which is surprisingly the same as British Standard Pipe Taper).
C= 3/4" BSPT Black Iron plug as available on such sites as eBay at £1.87. (You equally could go to your local plumbers and buy this item in Black iron or Galvanised for around £1.50). Note, this has a perfectly square drive which a 9/16 inch A/F spanner fits exactly.
D= 3/4" BSPF Stainless Steel Hex Head hollow plug from eBay at £2.35.
Note:- B, C and D are longer plugs and being Taper Threads, seal at exactly the same point as the shorter Plug A, they will protrude further out from the casing - not that these plugs are visible when in the car.











I don't want to be drawn on it, but the more US orientated NPT, (National Pipe Thread) at that diameter is also 14 threads per inch and although the thread profile is different at 60 degrees rather than the 55 degrees used on the BSP thread, this potentially could fit also at this particular inch size. Without getting into the details of using dissimilar metals, potential galling of stainless or alloy into other metals, high pressure sealing and the interesting Interference fits of specific fuel threads discussed in the previous post, we are talking about a filler/level plug operating in a vented non-pressurised environment. I would recommend a small amount of thread sealer for a complete effective seal and the choice is yours if you choose to change your plug.

Now back to more serious car stuff - Have fun !!

Dave

Good work Dave...very clear, detailed and to the poins.... Steve

Thanks Dave. The curious imperfect square drive on the OEM plug reflects its plumbing origins I think. My dad had some old spanners and the plumbing ones tended to be black iron too and crudely made 'blacksmith-style'. I imagine pieces of bar were heated in the furnace and a suitable slightly-tapered tool beaten through the flattened blob of red hot spanner to leave a kind of broached key that fit the crude tapered boss far better than precision mechanic's spanners. If you see one of those multi-use dog-bone drain plug spanners they have slightly tapered male and female ends.

Petep

Excellent summary thanks

As for the tools availble nowdays , I think we can list:
. A 14mm spanner but with difficult access and grip
. 8 points 9/16 socket as can be found on ebay US
. 14mm square socket such as this one
http://www.mister-auto.com/cle-et-outil ... 871-7.html

having received my 9/16 8 points socket, I confirm it works to undo the top "square" plug , with an angle rod

however there is some play, and I believe a 14mm square socket such as this one
http://www.mister-auto.com/cle-et-outil ... 871-7.html

would be better

Your post here helped me so much. I found it via a google search. It helped me find differential plugs. I found an aftermarket manufacturer here in the USA called Dorman. I found two 3/4" by 14 threaded plugs, one with a 5/8" hex head indent and a second with a half inch square socket extension indent. They fit perfectly.

What really helped me was that you mentioned that Subaru used JIS thread which is the same as British Standard thread. Thank you for you help.

Can you please link the 3/4" BSPF Nickel plated Allen key drive plug EBay item?

Hi Andrew....you should be able to get these quite easily from a local plumbers shop or hydraulic supplies..used on heated towel rails and radiators....at the top on opposite side to bleed valve.....also in stainless. ....Steve

mgcjag wrote: ↑

Fri Oct 09, 2020 8:01 am

used on heated towel rails and radiators....Steve

There's my problem

We don't have central heating in Australia. Searched EBay UK; hundreds of them!

oh yes i remember now...it was quite warm when i visited....

Hello. -73 e type series 3 differential.
Anyone know what this is? Was going to change diffoil on my newly aquired S3. And found a diff cover obviously not a standard part. It is a forged aluminum part with cooling fins. Were I expected to find level/ filler plug there is some kind of sensor with two cut off electrical wires, red and blue. Hold in place with two hold down bolts, one above and one below. The breather is capped off with a plastic cup cover. There is a forged in number btween cooling fins: 004H11 010-003
An after market «upgrade» with a temp sensor? Oil level sensor? Something from another model?
See photos.
Rgds Harald.

Looks like a later diff has been fitted, probably from an XJS. The plastic sender unit is for the speedo. Not needed on an E Type.

Thanks. A couple more questions arises. Is it possible that it is just the the diff cover that come from a later car, or would it be the complete diff?
Could I use the output from sensor to a XJS speedo? Guess that would be independent of actual final ratio. ( if complete diff is from xjs with internal side of sensor is present ) My speedo is very unaccurate, and speed indication is not consistent with odometer.
Final ratio have been changed at some point, probable from 3.51 ( us car w manual ) to 2,88.
Harald

If it is 2.88 then I would think it's a complete DANA diff from an XJS. I'm sure someone would be clever enough to fit an XJS electronic speedo but I think it's easier to get the original speedo overhauled and recalibrated.

Thanks. You are right about the speedo. And probable also about the diff itself. PO claims he had the crown and pinion gear changed to give a 2.88 ratio about 8 years ago. There is an old looking metal plate with 2.88 attached under one of the cover bolts. Maybe someone swopped the whole unit. It does have a drain bolt. Bolt pattern on cover looks similar to original, but does someone know if cover from a DANA diff actually fit an original diff? ( -73 e type s3 )
Harald.

Here's an 8 point square socket set on ebay:

https://www.ebay.co.uk/itm/333797881812

If the diff has a drain plug I don't think it can be a DANA diff. I can't confirm whether a DANA cover will fit an original diff but it looks like someone did it on your car.

Thanks.

swindler, nice tip.

Found tech info on jag-lovers saying that the DANA diff have three bolts holding bearing in place on the output shaft. Judging the boltpattern on the bolts I actually can see, there have to be more than three. Other diffs have five. ( same source )
Harald

Dana cover bolts are a different size as I recall. I have one of those XJS covers but ran into problems swapping a nice steel cover onto a tatty steel cover Dana diff. Threads were different so to bigger Dana bolts wouldn’t fit the earlier cover. Don’t recall if the size difference went the other way.