SC/CR gearbox

[steveshepstone]

I've managed to get my hands on a straight-cut close-ratio gearbox for my MGB. I used standard 20/50 oil in one I owned previously, any ideas/comments if this is still the best to use? Many thanks.

[Peter Cresswell]

Hi Steve
I am 95% certain you need to use 20/50 oil, as per a standard box, but to be 100% I suggest you give either MG Motorsport or Brown and Gammons a call to check. Both have competition experience with straight cut boxes.
If it is 20/50 you might like to consider protecting your investment by using Millers CTV 20/50. This is a semi synthetic oil specially developed for classic Minis and it has a hypoid component that protects the gears. I looked into using modern oils for the gearbox and you can read the response from Millers here:
http://mgbforum.mgb-register.org/viewto ... ?f=4&t=154
They also do a similar but fully mineral oil called Classic Mini 20/50, which may suit better if you have Overdrive as well as this has a cone friction clutch in it

.I had a 1967 Mini Cooper modified to S spec and used CTV 20/50 in that and it maintained 60psi even after a 25Km climb to the 2802m summit of the Col de la Bonette. A very impressive oil!

[steveshepstone]

Many thanks Peter. Just the confirmation I needed. Hope to fit the gearbox this week.

[Ian McKay]

Give Doug Smith a call at MG Motorsports...he is back from his skiing holiday in France this weekend...he knows a helluva lot about engine oils for MGB's. Seriously.

[Peter Cresswell]

I noticed recently that in the Moss MGB Catalogue, Technical Advice section, they recommend using EP80 Gear Oil with their straight cut gear set (their part number is STN70X). I have queried this with Moss Technical Support and this is their reply:
*********************
Hi Pete

You should use EP80 GL4 for straight cut gears STN70X because of the way they mesh together. You can use 20/50 engine oil in the helical gears.

Kind Regards,
R & D Technical Support
Moss Europe Ltd
********************
This has just to added to the confusion! As the previous posts from myself and Ian, I suggest you contact MG Motorsport or Brown and Gammons for a chat about. Incidentally many high powered racing Minis use straight cut gears and run on Millers CTV, including (I've just checked with Swiftune) Nick Swift's Clubman at Goodwood over the weekend. Using up to 9,200 rpm as well!

[steveshepstone]

Thanks everyone. More to ponder...... I had heard that EP90 was the oil to use but, specifically, in non-overdrive boxes only. I'm gong to use this box with 20/50 like I did with the last one. Watch this space!