1938 ENV Rear Axle

I drained my axle for the first time. Black and icky, my granddaughter says.

I looked in the 1938 Instruction Book and it says capacity is 3-1/2 pints. I presume that is Imperial pints, which converts to 4.2 US pints.

It says on page 14 to “Fill up to the level of the plug boss.”
I’m wondering which of the two plug bosses it means,

and why there is a dipstick on the front plug if you don’t use it.

I am inclined to guess that the instruction was written for the first axle used with engines L1 to L150, which according to the SPC J.2 page 26 has an oil level plug but does not have a dipstick.
Mine is L205.
What do you all think? Have I guessed right, do I use the dipstick?

BTW should the dipstick have a handle to unscrew it, like on my XK120?

Hi Rob,

Your dip stick looks just the same as mine. Just fill the casing to the line on the stick. Don’t use hypoid oil. There are yellow metal parts inside.


Answering my own question, no, there never was a handle. The dipstick shaft is 3/16" or .1875" diameter and it seems to have been screwed in and the upper end is mashed out. I tried to unscrew the shaft out the top from the plug, turned it about 3 turns to where I could see that there are threads in there measuring about .190", so the shaft was screwed in from the bottom, and would never unscrew out the top of the plug. Apparently the handle was a feature that came along later.

What parts are yellow metal, i.e. brass or bronze?

It’s 24 years since I was in there but I seem to remember that the bearing adjuster nuts were bronze.


Fairly sure the C spanned nuts are steel Peter, no doubt you are thinking of the front pinion adjuster.

Peter doesn’t mention brass parts on his page.

Here is a page about a similar axle in an AC saloon, also no mention of brass parts.

BTW in case it should ever come up in after dinner conversation, the thread of the drain plug is 3/8"-19 BSPT tapered thread, and the plug head is 13/32" square.

Whilst everyone is talking ENV Rear Axles again, I will resurrect my plea for any clues regarding the purpose of the C.305 BOX SPANNER, for REAR AXLE as included within SS-Jaguar and Mark IV tool kits…

The critical dimensions are as shown…

The SQUARE END is shown as the external 1/2" x 1/2" being the critical dimension, implying it is meant to fit inside a female square plug which to date no one seems to be able to find/identify on an ENV Rear Axle, nor indeed anywhere else on an SS Jaguar or Mark IV if the REAR AXLE description is in error (possible, but unlikely). So maybe showing the external 1/2" x 1/2" was the error, and the internal dimensions are actually what matters and its intended to fit over a male square plug, such as Rob’s described/dimensioned 13/32" Square Drain Plug - surely a likely candidate/application for a tool such as a C.305. Trouble is 13/32" = .406" and even assuming a 1/32" tolerance in the advised 13/32" dimension, 12/32" is still only .375", and when I measure an actual C.305 (as pictured) this one measures .501" x .502" external (so as per drawing), and with wall thickness of compressed tube about .09" the internal square measures .310" x .312" so no way will it fit over the 13/32" drain plug. Any further guesses of mine all suggest errors in the specifying of the C.305 Box Spanner…

So any other ideas???

And we can then talk about the hexagon end next - with its specified internal hex at .580" across-flats with my mint/unused example measuring at .576"/.578"/.576" presumably typical. Note this is NOT a standard Whitworth size as you would otherwise expect on an SS Jaguar/Mark IV REAR AXLE, being mid way between 1/4W (.527 - .530") and 5/16W (.602-.605") - according to the relevant pre-war British Standard for spanner hex sizes… being slightly smaller than the post-war revised British Standard…

Thanks Peter, I have been under the impression that there were bronze or brass parts in there but I certainly can’t remember exactly where they were. I don’t remember the pinion adjuster being yellow metal so perhaps I shouldn’t have avoided EP oils after all. It should be possible to see the pinion adjuster after removing the access plate.


p.s. I’ve just been reading the workshop manual for the Standard 12 & 14 and is says that EP oils should be used but don’t mix different brands. Apologies for the wrong suggestion about oils.

As you are aware Peter, the access plate with the dowel pin attached is for the rear pinion adjuster , this is steel.
The front pinion adjuster is yellow metal, at least this is what I recall. I machined some to fit a lip seal for the pinion flange
If I can extract my car from it’s home in the basement I’ll check !

Hi Peter,

It would appear that ENV or Standard and SS/Jaguar didn’t know or didn’t care about EP oils and the front adjuster. The 1937 Motor Trader article for the SS Jaguar also recommends EP.


Two possibilities.
The early Birman steering box has a small fill plug, but I can’t remember if 3/8 BSPT or 1/4 BSPT, whereas the later box has a 1/2 BSPT plug. I can’t find a 1/4 plug to check the square.
5.80 is near as dammit to 9/16 AF, and the U bolts for axle / spring fixation are threaded 3/8” UNF… The U bolts on my car ( donor 1937 saloon ) have the aforesaid 3/8” UNF thread but with large BS / Whit spannerr size nuts, but I have seen the U bolts held by the normal size 9/16” AF nuts.
Perhaps the 1/2 X 1/2 square end for a spanner?

Ha, ha. Ok I’ll confess, the reason I removed my drain plug was because, while looking for something else, I came across this in my 1939 British edition of Machinery’s Handbook.

I wanted to see if it was American thread, and would a countersunk or socket type plug fit there, thus solving the mystery of the C.305 box spanner. Nope, not this time.

My Burman steering box fill plug is about 29/32" or .906" average diameter and tapered with 14 threads per inch. That’s not 1/2 BSPT which is .834" major diameter. Nor is it 3/4 BSPT nor 1/2NPT nor 3/4NPT. Is there a 5/8BSPT? The square head is irregulary formed, 19/32 x 18/32 so not a candidate for using a C305 on it.

I wonder if there is a British Standard for these pipe plugs; I am disappointed not to find it in this book. I bought it on Abebooks from a shop in Wales.

One thing missing from Roger’s C.305 drawing is the tube wall thickness. Perhaps it was in the title box under Material Specification? The reason for giving outer dimensions on the square end may be related to the tooling used to make this end, squeezing it from the outside, and with a known wall thickness, the inside dimension would come out right.
Similarly the hex end was made by a .580" tool pushed up inside.

Well Rob ! after reading your post I thought, better check !
My plug is .88 min and .91 max on a thread length of 21 / 32 with the square drive @ 9/16 . So not 1/2”.BSPT.
So assuming (dodgy) that the early box plug is 3/8 BSPT what is the average square drive for same?

Yes there is … the relevant Standard is BS.21 BRITISH STANDARD PIPE THREADS (TAPER) and it quotes 1/8", 1/4", 3/8", 1/2", 3/4", 1" and so on up to 12" BSPT as standard, but does provide for alternate sizes such as 5/8"BSPT at 14 tpi, 0.0714" Pitch, .902" Major Dia and .8106" Minor Dia, so same 14tpi as 1/2"BSPT and 3/4"BSPT…


Nope, the C.305 Drawing (dated Aug 1939) only notes Material: Steel with nothing more than the dimensions as already shown in drawing, so no indication anywhere of wall thickness; thus my belief that it is the 1/2" x 1/2" square dimension that mattered, implying an intended application for an internal-square drive plug (or similar). My quoted - and with wall thickness of compressed tube about .09" the internal square measures .310" x .312" - is based on physically measuring an original C.305 Box Spanner. But as before, I am still clutching at straws, trying to work out purpose for this C.305 box spanner, before dismissing them as made/supplied in error… but being supplied to all 1938-40MY SS Jaguar, drawn up in August 1939, then supplied again to all post-war Mark IV and Mark V this is a long time with a few major opportunities, not to have fixed any error or deleted its ongoing supply… :joy:

Ok, so the Burman filler plug is 5/8"-14 BSPT which is an allowed but non-preferred size. I don’t see any particular reason why they would use it rather than 1/2" unless they found a whole bunch of them for free.

Peculiar that there would be no wall thickness or steel type specified on the C.305 drawing. That’s basic requisite information. If I was the engineer checking it, I would mark in red “missing dimension” on it and send it back to the draftsman. Otherwise the supplier could make them in .020" wall Grade B and expect to be paid.