What oil do I use in my SR gearbox

[rowan.bradley]

I am planning the rebuild of my 1958 Super Rocket. I know the engine needs a full rebuild, but as far as I remember from 50 years ago, the gearbox worked OK. Since then it has sat there doing nothing. Am I taking a risk if having rebuilt the engine I simply change the oil in the gearbox and start using the bike, and see if any problems develop with the gearbox? Or do I need to strip it down and examine things (bearings, oil seals etc.) to make sure everything is OK before riding the bike? Are there things that I should definitely plan to replace (e.g. oil seals) before riding the bike?

What oil do I use in the gearbox? I have seen elsewhere that 80/90 gear oil is best, but does this need to be hypoid oil? Or does it need to be non-hypoid? Or does it not matter? Can I flush the gearbox out with anything to minimise the amount of 50 year old oil that remains before adding the new oil? If so, with what?

Many thanks - Rowan

[morris]

Penrite gearbox 30 does it for me.
http://www.penriteoil.com.au/products/gear-box-oil-30
While the box is out, you could also install a new sprocket seal and an SRM sprocket nut to eliminate leaks from the final drive.

[Topdad]

I can feel people twitching already at the prospect of an oil thread !!I'd say it's agreed that all oil is better now than back when our bikes were new.  choice therefore is down to the individual and options he incorporates ,for instance fitting  an inline filter would enable use of a multi grade ,(but some members run multi without ) others ,myself inc run on straight 30 or 40 grade .
Probably more important is that during the rebuild you clean out the sludge trap on the crank as even the best oil in the world won't stop your drive side  conrod exiting the cases with a bang  if the the oil flow to it is stopped by  a clogged trap!
search oil and you'll see any number of previous posts on this .Oh i use engine oil (40 ) in my g/box. cheers Bob.

[muskrat]

G'day RB.
The book says 40 or 50. I use whatever is in the engine Penrite 20W60 or 25W70 and for extra "slickness" I add
https://www.nulon.com.au/products/specialty-products/manual-gearbox-and-diff-treatment
Cheers

[KiwiGF]

I am planning the rebuild of my 1958 Super Rocket. I know the engine needs a full rebuild, but as far as I remember from 50 years ago, the gearbox worked OK. Since then it has sat there doing nothing. Am I taking a risk if having rebuilt the engine I simply change the oil in the gearbox and start using the bike, and see if any problems develop with the gearbox? Or do I need to strip it down and examine things (bearings, oil seals etc.) to make sure everything is OK before riding the bike? Are there things that I should definitely plan to replace (e.g. oil seals) before riding the bike?

What oil do I use in the gearbox? I have seen elsewhere that 80/90 gear oil is best, but does this need to be hypoid oil? Or does it need to be non-hypoid? Or does it not matter? Can I flush the gearbox out with anything to minimise the amount of 50 year old oil that remains before adding the new oil? If so, with what?

Many thanks - Rowan

I think you will be ok just changing the oil and giving it a go, apart from checking it spins ok without grinding noises etc an "external" check worth doing is for a worn bush on the main shaft, called a sleeve gear bush. Just check if there is any obvious play in the mainshaft....if there is ....then it's strip down time. A few thou is ok but not (say) 010". The rubber seal on the sleeve gear may well have perished and may leak a little but it's probably worth risking in your situation, I can't remember if that can be replaced without a gearbox strip, maybe someone else can advise?

I use castrol gtx 20/50w in my gearbox (and engine) which works fine, forks as well for that matter. A thick 80/90w grade gear oil is NOT ok for the box.

Edit: I would not flush the box, but maybe change the oil after it's got hot and after a few initial trial runs.

[duTch]

 The drive sprocket seal can be changed on a swing arm model without a strip-down.  Just need to remove the inner chaincase....
 I think I use Castro 85w90 in my box, and don't have issues but my climate is a bit warmer than yours.

 You might find third gear a bit 'noisy', that's to let you know you're in third- should have a part number but somehow missed the list  if not you're lucky..

[BSA_54A10]

Gear oils and engine oils use different viscosity ratings.
A 30wt engine oil is around 50w gear oil.
Any manual CAR gear oil will be fine as will syncro safe truck oils.
However oil designed for crash boxes as found in big trucks, tractors and some plant will not be OK as it still contains sulphur.

[KiwiGF]

After reading this https://en.m.wikipedia.org/wiki/Gear_oil should you take the risk of using a gear oil? When it appears the "most" (quote) contain additives harmful to copper based alloys?

Yes some types can used safely but is it worth the risk and/or bother of finding out for certain if they may mess up the bushes in a gear box?

I had new sleeve gear bushes fail after using a gear oil, I'm not certain if it was the higher viscosity, or additives, or rubbish bushes that caused the failure, but I personally won't risk using it again.

[Black Sheep]

Morris lubricants make gear oil for classic machines. Just the right kind of additives.

[BSA_54A10]

After reading this https://en.m.wikipedia.org/wiki/Gear_oil should you take the risk of using a gear oil? When it appears the "most" (quote) contain additives harmful to copper based alloys?

Yes some types can used safely but is it worth the risk and/or bother of finding out for certain if they may mess up the bushes in a gear box?

I had new sleeve gear bushes fail after using a gear oil, I'm not certain if it was the higher viscosity, or additives, or rubbish bushes that caused the failure, but I personally won't risk using it again.

The  big problem with unsubstianted rubbish you see on the web is most of it is rubbish put on there to inflate the ego of the poster, many of which know absolutely nothing about what they are posting but just cut & paste from real web sites ( like the two quoted ).
1)  SYNCRO CONES ARE BRASS thus any oil designed to go in a syncromesh gear box, which is about every manual car box made since 1960 will be fine in a BSA gearbox
2) gear oils are not heavier than engine oils they are lighter because the viscosities are measured differently
3) modern gear oils are in the range of 5 W to 10 W and both of those would be less than a 0 W engine oil

From the 60's to around the 80's gear box oils were marked "syncro safe" if they did not have anything that attacked copper based alloys ( yellow metals really? ) however once syncro boxes became the norm and most of the old bangers running crash boxes had their appointment with Mr Simms the oil companies went the other way and labeled the sulphur oils as "unsuitable for syncromesh gear boxes.
Now days most truck boxes are also syncro so most truck gear oil will also be fine.

back when BSA parts were hard to come by a lot of idiots made up sleeve gear bushes
1) without the 3 oil entry holes
2) without an oil gallery
3) without the proper shaped clutch end
4) without the oil reseviour in the middle ( usually done by using 2 short bushes )
5) out of the wrong materials,

Owners also decided that the felt placed on the end of the sleeve gear bush by the engineers at BSA to protect the end & prevent grit getting into the bush was not necessary so omitted it when they changed their sprockets

[Angus]

A Gearbox oil tread and nobody has mentioned EP90 -GL4 which on a thread earlier this year was recommended and thus what I changed to. Please don not change your minds. Its in both boxes and they are performing great. see https://www.a7a10.net/forum/index.php?topic=11603.msg88568#msg88568

[BSA_54A10]

Well that is because I am using Agtrans 120 in all my BSA's for a long time as I just inherited 40 liters of it.
When that runs out I got another drum of Agtrans 90.

People fuss so much about oils
Get out and ride the thing,'
back in the 60's 70's & 80's the bike was lucky if it had any oil in the box and what went in when low was whatever was at hand.

Thses bikes are dinosaures of the transport era , not a modern high performance car shoving 400+ Hp through a slick low drag box & LSD.

Some times I wonder if people ar scarred to ride their bikes and just looking for an excuse to pull it apart again.

[Angus]

Yes I agree Trevor using them is key and they used to be treated very badly and still came back for more.
I will be honest and say it was the first time I had EVER actually changed the A7's (owned since 1976) or the A10's gearbox oil. Just did not want to find I had put something bad in as I do use both. This year the A7 has had 2 in year oil changes 2700 miles and A10 has done about 1500 and even the Norton (it runs now) has done 500. Not huge mileage but it was all fun . I like to treat them nice as I dont want them broken on the bench.