Trying to work out what size allen key fits the type 9 gear box before i grind down my 10, 8 and 6! Need to do an oil change and it's such a tight squeeze to get to it I'm not sure what size allen key is required! Any advice welcome, and any tips and tricks for the change appreciated!
Thanks
Rhys
Rhys,
Its 10mm but I've always used a chopped 3/8" on mine.
You can also get replacement OEM plugs with a square hole that a std ratchet will fit.
Ian
Here are a couple of pictures of one I cut with a dremel. It worked well. I think the plug is often tight. The tape is to reduce scratches on the chassis rail.
I used an oil pump to drain it and a large oil syringe body as a funnel to fill from above. Patience is definitely a virtue in the process. There is another recent thread on it from a few months back.

Thanks for the reply Ian, don't think I could fit a ratchet up through the gap!!
Just seen the thread!! Sounds like a fun job!!
The best advice i had when doing mine, although a different type of box, was to make sure you undo the fill plug first, as you dont want to have drained it all and then find out you cant open the fill plug. As it turned out this was excellent advice as the fill plug was a complete nightmare to open, where the drain plug was really straightforward.
R500sv
'Bravery is being the only one who knows you are scared'
I cut mine a bit longer. Also slipping a bit of tube over the key to extend the handle gives some extra oomph!
PS - I have a couple of new surplus 3/8 allen keys if you want me to post one, save sacrificing one from your set. Drop me a PM.
As above +
... on many Sevens you can cut an access hole in the transmission tunnel to give direct access to the plug. (On some there's a chassis member in the way.)
... if you use a ratchet wrench on the hex key stub make sure that it's the type that you reverse by moving a lever and not the type where you have to turn the handle over... I may have related this saga before... ; -(
Jonathan
"Any advice welcome, and any tips and tricks for the change appreciated!"
Detailed notes from Alcester Racing Sevens. (That's now on The Wayback Machine.)
But I think that most of the points are now covered in this thread.
There's a very large number of threads on this exact topic. Some notes on searching, as many of us can't find what we need using either of the site's two built-in search functions. I suggest trying the one that's in my Signature at the bottom of this post.
Jonathan
A type 9 gearbox doesn't have a drain plug, only a level/filler plug. Hence the need to symphony/pump it out.
I thought 2020 was the year that was going to give me all I wanted. It turned out to be the year to make me appreciate what I've got.