S3 short end allen key for gearbox filler plug

43 posts / 0 new
Last post
Wrightpayne's picture
Last seen: 5 min 38 sec ago
Joined: 17/04/2014

I cannot visualise this - have you got a pic or sketch to show what you have done?

On my car with original 5sp sierra box and now 6sp caterham box I've never had any difficulty with the fill plug. I always go under the car from the opposite side to the plug so your fingers naturally bend towards the plug. Plug between both index fingers and push one up / one down to turn the plug.

I have a cut down allen key to 'crack' it undone then use above method to remove. I sometimes add a bit of steel tube over allen key to add leverage and get my knuckles away from anything sharp! 

Last seen: 9 hours 39 min ago
Joined: 23/08/2015

#12 That's basically what I do but with the cut off Allan key, 10mm spanner (or is it 3/8", I forget) on it and a tube over that to crack. Then a couple of turns with the spanner and the Allen key can be removed and the plug taken out by hand. 

I can see the risk of screwing out until hitting the chassis panel and being stuck but never had that issue. I'm pretty sure the plug would be out before my bit of Allen key hit the panel. 

I have an SV though, maybe it's a touch wider there? 

Jonathan Kay
Jonathan Kay's picture
Last seen: 21 sec ago
Joined: 17/04/2014

And perhaps not all lengths of key are created equal!

: - )


Drumster's picture
Last seen: 8 hours 21 min ago
Joined: 17/04/2014

This had been a very useful set for those tight fitting spaces. Purchased from Halfords many years ago but not sure if it's still available?

Member since March 1998

Mrp's picture
Last seen: 8 hours 8 min ago
Joined: 17/04/2014

I've got the same #15

Mrp 420R

john milner
john milner's picture
Last seen: 1 month 2 weeks ago
Joined: 17/04/2014

I have a set of drain plug keys and one just about fits but it is very tight. SV chassis and five speed Sierra gearbox.

I would not recommend using any form of ratchet unless you are sure you will not trap it in the reducing space.

I have never seen a bulk buy of cut down Allen keys.

Last seen: 9 hours 39 min ago
Joined: 23/08/2015

It's not hard to cut an Allen key with a Dremel.

Following this thread I've bought an extra long 10mm double ended ring. Ratchet at one end plain the other. 292mm long.

I've cut a piece off a 10mm Allen key, after grinding the end down to .375" hex so now I can use the same long spanner on both the drain and fill. (6 speed)

I started the job just to see if I could grind down the hex accurately enough by hand and it was fairly easy, you're only taking 0.25mm off each flat, and it fits the socket very well. 

I'm aware of the trapping risk but my intention is to make the stepped Allen key short enough to eliminate that risk.  (Or be very careful!)

timb2117's picture
Last seen: 2 months 4 weeks ago
Joined: 26/04/2020

Basic, low rent but works a treat.


grumpy the 7th
grumpy the 7th's picture
Last seen: 8 hours 28 min ago
Joined: 17/04/2014

All of the above suggestions work except the hole in the tunnel side, I've got a diagonal frame that just obscures the drain plug.

I use the spanner and cut down 10mm hex key BUT also put a bit of gaffer tape over the hex bit and press it into the ring before cracking the drain plug. That way you don't have to get out from under the car to look for something with flat sides that falls out and rolls for yards to the other side of the garage.

Bakewell, I prefer a tart

TexasDreamer's picture
Last seen: 3 months 3 weeks ago
Joined: 08/03/2021

Whats the best method for getting the oil in without dripping it on the seats and carpet? 

TexasDreamer, 1992 Caterham Super 7, 1700