TR3 Oil filler plug spanner

[PXC]

Hi

Has anyone got one of these spanners surplus to requirements, for sale - 2 square holes, one for brake adjustment, one for engine, and gearbox oil level/filler plugs? Part number RX1643.

Thanks

Paul

 

 

[Lebro]

I think you will find that both ends are for brake adjustment. Too small for gearbox etc drain plugs.

Bob

[james christie]

Why not solve your gearbox and engine sump plug problem by welding a suitable nut onto the square edged plugs, next time you take them out.

Don't 'alf make life easier and you can use a ratchet and socket - well maybe not on the  gearbox filler plug.

james

[PXC]

That’s a good tip James. It’s the gearbox filler/level plug that I’m addressing. I first have to get existing one out. It’s a bit rounded, and I don’t believe it has ever been out for many years. I have drilled a 25mm hole in the tunnel directly opposite the level plug, but that’s only useful if you can find a socket, or pipe spanner, to fit the square nut tightly, which I can’t.
It is poss to drain it from the drain plug, the refill from the top. As it happens, my gearbox has a large hex headed plug on the top, which I can fill through. This seems none standard for a TR3. 
 

I’ve filled up now, so when the “off” season starts, I’ll get the transmission tunnel off and get that plug out. 
 

regards

Paul

 

[John Morrison]

Hi Paul,

I picked one of these up at an autojumble years ago, 

Appently it is a wagon, brake adjusting spanner - works really well, but of no use for access to

the GB filler plug, because of the flange on the side of the GB. So I found a redundant, 1/12 socket and 

welded it the 'Wrong' way onto the other end.

Its never failed to remove even a rounded off filler plug.

 

Paul, if you weld its a doddle to weld any old 1/12 socket onto a bit of bar or flat, if you don't weld let me know and I'll knock

something up for you.

John.

 

[PXC]

Yes the flange is the complication- that’s why I’m going in from the side through the tunnel. But that’s a genius idea John. I’ll try a back to front socket on the square nut first. 
I got the digital caliper onto the square nut and got a reading of 11.2mm, which made me think it should be 7/16” AF. But maybe it’s just a bit worn and a 1/2” socket drive will still be tight enough to move it. (The new plug, which I have from Rimmer, is 12mm AF).

I’ll probably weld an old socket backwards onto a short 1/2” square drive extension then I can go straight through the 25mm hole in the side of the gb tunnel. Easier than grovelling under the car. 
 

Thanks for the offer of welding, I have a local chap who will help me out there, but if needs be I’ll come back to you. 

Regards

Paul

 

[Ralph Whitaker]

10 hours ago, PXC said:

Yes the flange is the complication- that’s why I’m going in from the side through the tunnel. But that’s a genius idea John. I’ll try a back to front socket on the square nut first. 
I got the digital caliper onto the square nut and got a reading of 11.2mm, which made me think it should be 7/16” AF. But maybe it’s just a bit worn and a 1/2” socket drive will still be tight enough to move it. (The new plug, which I have from Rimmer, is 12mm AF).

I’ll probably weld an old socket backwards onto a short 1/2” square drive extension then I can go straight through the 25mm hole in the side of the gb tunnel. Easier than grovelling under the car. 
 

Thanks for the offer of welding, I have a local chap who will help me out there, but if needs be I’ll come back to you. 

Regards

Paul

 

They are indeed 7/16 originally, but as they are basically a plumbing fitting they tend to be a tapered profile on the head which is why a 1/2 inch  square socket will sometimes fit and undo them. You can buy the correct socket for them, I have 2, a 1/2 inch drive and a 3/8 drive, but instead of being 12 point for a six sided nut, they are 8 point for square nuts.  If when you get it out you want to replace it take it down to your local plumbing supplies emporium who I am sure will be able to provide a replacement.

Ralph

[PXC]

Well I tried a reversed 1/2” drive socket short extension, it didn’t budge and I just managed to round it off a bit more. So it will have to wait until I can take off the tunnel, and get an angle grinder on to square it up again, then a good fit tool of some sort. 
luckily, as explained above, I can still fill and drain the box by other means. 
cheers

Paul

 

[Brianjone5]

On 9/4/2025 at 8:57 AM, Ralph Whitaker said:

They are indeed 7/16 originally, but as they are basically a plumbing fitting they tend to be a tapered profile on the head which is why a 1/2 inch  square socket will sometimes fit and undo them. You can buy the correct socket for them, I have 2, a 1/2 inch drive and a 3/8 drive, but instead of being 12 point for a six sided nut, they are 8 point for square nuts.  If when you get it out you want to replace it take it down to your local plumbing supplies emporium who I am sure will be able to provide a replacement.

Ralph

I bought a 7/16 square pipe plug socket. It fits the tapered plug perfectly snug on all four sides.

https://www.amazon.co.uk/dp/B006L23G0W/ref=pe_27063361_487055811_TE_3p_dp_1

[Charlie D]

On 9/3/2025 at 8:25 PM, PXC said:

As it happens, my gearbox has a large hex headed plug on the top, which I can fill through. This seems none standard for a TR3. 

Paul,

I'm intrigued by this !

Next time you get a chance can you post a picture of it.

Charlie

[Lebro]

I thought you had a saloon box?  This is a 1972 saloon box:

I have added the 2nd gear overdrive switch, & the dipstick.  no hex headed plug, but from memory yours was blanking off the 2nd gear overdrive switch hole.

which a saloon box should not have, so maybe not one.  later TR box perhaps 

Bob

[Brianjone5]

On 9/3/2025 at 5:39 PM, Lebro said:

I think you will find that both ends are for brake adjustment. Too small for gearbox etc drain plugs.

Bob

Actually, no. Rimmer supplies such a spanner: one end for brakes, the other the 7/16" drain plugs

https://rimmerbros.com/Item--i-RX1643--SelectedCurrency-1?utm_content=mediabuy&gad_source=1&gad_campaignid=22140097117&gbraid=0AAAAAD500i_uE0x-9Ad6s1wssfiH-oCBP&gclid=Cj0KCQiAosrJBhD0ARIsAHebCNoW9X8b0NDp9nn6nEY7uURGlNBW1iBTfyrVJQYBfv_agHelxW4HaQ8aAg23EALw_wcB

[PXC]

On 12/5/2025 at 9:53 AM, Charlie D said:

Next time you get a chance can you post a picture of it.

 

[Charlie D]

That (I think) is the normal dip stick hole.

Bob made his own dip stick to fit. Maybe he can give you the dimensions to make one. (Useful thing.)

[Lebro]

No, it is the place where an overdrive inhibitor switch could go. the location for a dipstick is the bulge furter forward on the right hand side.
you can just see my dipstick top on my image above this one.

Bob

[Drewmotty]

I drill and tap the dipstick boss on late gearboxes 3/8 BSP to use as a filler. 

[Charlie D]

10 hours ago, Lebro said:

No, it is the place where an overdrive inhibitor switch could go.

Ahhhh... of course it is.

If you tried to put the dip stick through there it would hit the selector rod.

[PXC]

I like the idea of having a dipstick, particularly just now when I think I might have a gearbox leak.
When drilling and tapping that boss for a dipstick, what do you do about the swarf dropping into the gearbox? Can it be just flushed out? Or is that operation one you should do only with the gearbox out, drained, and on its side?

Bob, did you acquire, or make your dipstick?

Paul

[AJ2014]

Another photo which may help to see the dipstick.

Regards Ade

 

Edited December 7, 2025 by AJ2014
Picture added

[Lebro]

3 hours ago, PXC said:

I like the idea of having a dipstick, particularly just now when I think I might have a gearbox leak.
When drilling and tapping that boss for a dipstick, what do you do about the swarf dropping into the gearbox? Can it be just flushed out? Or is that operation one you should do only with the gearbox out, drained, and on its side?

Bob, did you acquire, or make your dipstick?

Paul

  

Made my own.   Alignment of the rod in the gearbox is quite important, as it runs very close to the gears.

Bob

Edited December 7, 2025 by Lebro

[Charlie D]

41 minutes ago, Lebro said:

Alignment of the rod in the gearbox is quite important, as it runs very close to the gears.

Mine was too close.

[RogerH]

That would have sounded like our school days bikes with a fag packet running on the spokes.  

[Don H.]

On 9/4/2025 at 6:35 AM, PXC said:

Well I tried a reversed 1/2” drive socket short extension, it didn’t budge and I just managed to round it off a bit more. So it will have to wait until I can take off the tunnel, and get an angle grinder on to square it up again, then a good fit tool of some sort. 
luckily, as explained above, I can still fill and drain the box by other means. 
cheers

Paul

 

I've used a small pipe wrech to take drain plugs off my TR in years past.  If you have access and get get one of these on the plug, it'll get mangled, but it's comin' off!

[PXC]

18 hours ago, Don H. said:

used a small pipe wrech to take drain plugs off my TR

Yes, I’ve got past that problem now, once the tunnel was off I could get proper access to it. 

[PXC]

22 hours ago, Lebro said:

Made my own.

I thought you would have, very nice. 
I also see the selector cover off for drilling the boss out - I didn’t think of that. 
Regards

Paul