Gear oil grade

Started by Phil C, 05 Jun, 2018, 13:03

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Phil C

05 Jun, 2018, 13:03
What oil should I use in the gear box of my 1965 B40F?  I thought it should be EP90, but there don't seem to be many straightforward EP90s. Is 80w-90 suitable? Also, what is GL4?  Phil.

AWJDThumper

#1
05 Jun, 2018, 13:43
Having just checked the owners manual, it surprisingly seems to recommend the same oil in the engine and gear box!

Phil C

#2
05 Jun, 2018, 15:37
Yes, I saw in the Haynes manual that Castrol GTX 20w50 was recommended, and so thought about using the same stuff I have in the engine (Comma Classic 20w50.)  But I see that in Nigel Clark's book "Classic Motorcycle Restoration and Maintenance" (I have the books but not a clue!) EP90 is recommended. Rupert Ratio vol 1 (p.42) tells us that EP90 was not originally recommended by BSA as there was a possibility of the gearbox oil seeping along the gearchange shaft, kickstart shaft and from the gearbox main shaft bush, to mix with the engine oil. RR goes on to say that this is not possible in the sidepoints engines. Mine is side points, so I guess I'll look to use EP90.  But as I say, the shops don't seem to have much in the way of straightforward EP90.  Maybe I'll look on-line.  I suspect that, as I think someone suggested when I was posting about primary chaincase oil, I might be over-thinking this - maybe it's not all that crucial.  But anyway, I'll look on-line for EP90.   Phil.

JulianS

#3
05 Jun, 2018, 16:16
Some gear oil specifications are not recommended for boxes with phosphor bronze parts - bushes.

Suggest see the Morris website for classic oils and read the technical information for the products they offer.

https://www.morrislubricants.co.uk/catalogsearch/result/?cat=0&q=classic

Using Morris 20/50 in my A10 needle roller box with no problems. Have also used Halfords gear oil to GL4 spec with no problems.

AWJDThumper

#4
05 Jun, 2018, 16:18
Modern practice is to use the same oil in motorcycle engines and gearboxes (actually, the same oil) and so, if it's good enough for these, it's going to be good enough for a B40. As indicated by RR, a heavier oil (eg EP90) will give the gearbox a longer life in principle but the rest of the engine (valves, cylinder, etc) will probably have worn out a long before that!

Phil C

#5
05 Jun, 2018, 16:56
Wish I'd read this before I ordered the EP90!  Oh well, I'll know in future.  Thanks, AWJDT.  Phil.

Phil C

#6
05 Jun, 2018, 18:34
Just seen your post, Julian.  Thanks very much, but, as I say, I've ordered some Castrol EP90, which I assume will be fine.   Phil.
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