which oil for 6 speed box

which oil for 6 speed box

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Discussion

analog_me

Original Poster:

287 posts

128 months

Saturday 15th September 2018
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Hi all,

I would like to change the oil of my 6speed box, do you know what to go for?
I remember having read several time the best one is the standard one for reduced noise and feel but which one is this?
also is there a point in getting a slightly more viscous for a tired box?
Thanks

CycleSi

504 posts

192 months

Saturday 15th September 2018
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Redline MTL.

tomwoodis

570 posts

183 months

Sunday 16th September 2018
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Seconded, Redline MTL is the one to use

anonymous-user

53 months

Sunday 16th September 2018
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I changed the standard Comma for MTL after about 2000 miles.

A small but definite improvement in smoothness of change.

viper blue

166 posts

163 months

Sunday 16th September 2018
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I stick with comma manual gear oil EP75W80 plus GL4.
Get it from your local Halfords. I have used this in my 6 speed for the last 10 years. No problems.
It is a mineral base, the same type as Caterham fit. I have tried semi-syn but fine the box is happy with the mineral.
There are a few posts on the web that mtl is too slippery for the box’s synchros. Much view and discussion on this point.

Edited by viper blue on Sunday 16th September 18:35

analog_me

Original Poster:

287 posts

128 months

Sunday 16th September 2018
quotequote all
Thank you,
As per my internet search the filling point is on the side and needs to be filled in until it starts to overflow but how much is this in liters?
Furthermore is there a bottom drain on the box to remove the old oil ?

fergus

6,430 posts

274 months

Monday 17th September 2018
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viper blue said:
I stick with comma manual gear oil EP75W80 plus GL4.
Get it from your local Halfords. I have used this in my 6 speed for the last 10 years. No problems.
It is a mineral base, the same type as Caterham fit. I have tried semi-syn but fine the box is happy with the mineral.
There are a few posts on the web that mtl is too slippery for the box’s synchros. Much view and discussion on this point.

Edited by viper blue on Sunday 16th September 18:35
They do an "NS" (non slip) version. I use this in my rebuilt 1960's Alfa Romeo box (with modern synchros) and the standard MTL product in my Caterham 6sp box.

I'd speak to Phil @ Road and Race Transmissions if you want chapter and verse on the Caterham box, it's foibles and the recommended oil.

anonymous-user

53 months

Monday 17th September 2018
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analog_me said:
Thank you,
As per my internet search the filling point is on the side and needs to be filled in until it starts to overflow but how much is this in liters?
Furthermore is there a bottom drain on the box to remove the old oil ?
Yes, there is a bottom drain and from memory you’ll get about 1.8 L or so in. The MTL comes in US quarts, about .95 Litres

I cut down an Allen key to fit in the level plug, which I turn with a 10mm spanner.

I pump the oil in with a Sealey Mini Pump. It’s pretty straightforward.

DCL

1,215 posts

178 months

Monday 17th September 2018
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MTL certainly works well but needs a caveat in terms of gearbox wear. It works by increasing friction between the synchro cone and rings - essentially removing any polishing of the synchro surface. But that results in faster wear, and wear rate that may be important to you. I found using MTL to 'rejuvenate' the box every now and then, and then changing to a conventional GL4 oil gave the best of both worlds.

V7SLR

456 posts

185 months

Tuesday 18th September 2018
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Mine previously had MTL but I started to question whether the noise was doing the gearbox any good ... swapped to a regular GL4 oil and the box runs much quieter. When cold there's a slight drag going into 2nd but this disappears within half a mile of use, absolutely no difference in shifting when warm. My car's predominantly road use with an occasional track day, I've decided a normal gear oil is more appropriate for my use.

anonymous-user

53 months

Tuesday 18th September 2018
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V7SLR said:
Mine previously had MTL but I started to question whether the noise was doing the gearbox any good ... swapped to a regular GL4 oil and the box runs much quieter. When cold there's a slight drag going into 2nd but this disappears within half a mile of use, absolutely no difference in shifting when warm. My car's predominantly road use with an occasional track day, I've decided a normal gear oil is more appropriate for my use.
Why the reference to GL4? MTL is GL4.

It’s odd how different users have different perceptions. I’m not aware of any change in noise, though the gearbox is pretty quiet in any case.

I did perceive an improvement in the smoothness of change when I started using MTL but haven’t ever noticed any ‘drag’ when cold, whichever oil. Having said that I always go slowly through the box until it’s warm so maybe I wouldn’t.




V7SLR

456 posts

185 months

Tuesday 18th September 2018
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I swapped to a “regular GL4” ... as opposed to a “specialist GL4” which is how I would describe MTL.

analog_me

Original Poster:

287 posts

128 months

Thursday 11th October 2018
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As I was looking into how to best replace the grearbox oil I discovered since the last two years and 8000 miles I own the car a plug is missing from the gear box driver side above and behind the speedometer pickup point, close to the gear lever. Do you know that this is?
It is in the place the red plug is located in the caterham website showing the 6speed gearbox.
https://caterhamparts.co.uk/gearboxes/5204-gearbox...


Edited by analog_me on Thursday 11th October 21:17

downsman

1,099 posts

155 months

Friday 12th October 2018
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That is the hole the speedo drive goes into the gearbox from. There is a much smaller plug opposite that the old mechanical speedo drive comes out of.

analog_me

Original Poster:

287 posts

128 months

Saturday 13th October 2018
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My old mechanical speedo is where the yellow plug of the picture is, further forward and lower down.