The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: RogerSB on 23.05. 2019 20:18

Title: Gearbox protection
Post by: RogerSB on 23.05. 2019 20:18
On a few runs recently I've detected a slight chattering (best I can describe it) noise when in 2nd and 3rd gear with either a light throttle opening or when throttling down. I don't detect it in 1st or 4th or when accelerating, even hard. The problem is when riding it's difficult to know exactly where it's coming from but as I only get it in those gears and when riding I imagine it's from the gearbox.  Without stripping it down to look I thought I may try something like this first (see pics).  My thinking is, if it makes a difference I'll know for definite where it's coming from.

Has anyone had any experience using either of these products in their gearbox?
Title: Re: Gearbox protection
Post by: RDfella on 23.05. 2019 20:51
Not sure additives will help. Many years ago I tried an additive in a racing engine. It seized up shortly after.
Have you checked the cush drive, primary chain, etc?
Title: Re: Gearbox protection
Post by: RogerSB on 23.05. 2019 21:24
Not sure additives will help. Many years ago I tried an additive in a racing engine. It seized up shortly after.
Have you checked the cush drive, primary chain, etc?

Hi RDfella, thanks for your reply. SRM 4 spring clutch fitted end of 2017, along with SRM's cush drive nut tightened to 60psi with loctite and a new Regina primary chain. Primary chain was checked recently and was ok (1/2" at its slackest point). Also secondary chain new at the same time and is adjusted correctly. It's not the clunking tapping you get from a slack chain, it's more a light scuffing chattering noise. As I can't detect any unusual noise while in the other gears it leads me to think it's probably from the gearbox, which is filled with 14 fl oz of Halfords 80W/90 GL4 gear oil. I was thinking of adding either the Slick or MolySlip to that - just to see if it has any effect on the noise I'm hearing (edit: which could confirm or rule out the gearbox).
Title: Re: Gearbox protection
Post by: dave55 on 23.05. 2019 22:43
Hi Roger, have used the top one in a old MG I had in the 70,s I though it made some difference, but then again I thought go faster stripes did too, something which did make a difference to the gearboxes in the factory I worked in was PTFE shavings, the gearboxes were quite expensive and we could only rebuild the noisy ones in August shutdown unless it failed all together ,so if it was noisy in say March standard practice was to get a tin of these shavings from the stores and put them into the gearbox oil whilst machine was running until you noticed a quieter tone. We never had a failure due to them and when the gearbox was stripped the gears had a coating on mating faces of PTFE .
The shavings looked like soap flakes of a smaller size and were meant to be used for gland packings in water based hydraulic presses, I  am not to blame if any one tries it and buggers up the gearbox though . Cheers Dave
Title: Re: Gearbox protection
Post by: Greybeard on 23.05. 2019 22:52
Roger, this sounds very much like my experience a couple of years ago. I did try Molyslip to improve notchy changes. One day I arrived at Cheshire camp sounding like a coffee grinder. I had the box professionally overhauled. It's been super smooth since then.
Title: Re: Gearbox protection
Post by: orabanda on 24.05. 2019 01:56
Local folklore was if you had a noisy gearbox in your car (Holden or Ford),
then add a couple of bananas to quieten it down, and sell it!

In your case Roger, might be best to pull it apart.

Richard
Title: Re: Gearbox protection
Post by: Black Sheep on 24.05. 2019 06:41
Of course, should any gearbox oil with Molyslip seep along to your clutch, you might have to add add clutch plates to your shopping list. A proper investigation is what's required.
Title: Re: Gearbox protection
Post by: Swarfcut on 24.05. 2019 07:53
My money is on the layshaft blind bush.  There is more  load on it in the intermediate gears, a pointer to the problem, as the load is transmitted further towards the bush as 2nd and 3rd are engaged. No load in top (direct drive, mainshaft locked to output drive sleeve). First gear engaged puts the main load at the other end of the layshaft.  A little bit of rattle in the bush will allow it to dance on light throttle or over run.

 Assuming you box has the standard (worn and knackered) bronze bushing, and the heavily scored standard layshaft.

 No, not really Roger, only joking.

 Swarfy.

 
Title: Re: Gearbox protection
Post by: BSA_54A10 on 24.05. 2019 09:40
BSA boxes are designed to be run in SA30 oil.
Running anything much heavier than 50 will cause excessive wear in the layshaft bush which will not get enough oil.
Way way way back, I took some advice and used NLG 000 liquid grease to stem the flow of oil from the pre war box
Now the adviser was a well known repairer but what I failed to realize was he does around 100 miles a year max on any one of his dozen or so bikes, so the excessive wear was never going to be a problem for him.
However I was putting 20,000 miles a year on my bike, so the gearbox lubrication problem became chronic but not before it destroyed the entire box.
The only useable parts were the mainshaft and forks everything else including the case was wrecked.
Not sure about how Molly slip changes the oil flow within the box but surfices to say, my box ran quiet & drip free till it didn't.
Title: Re: Gearbox protection
Post by: muskrat on 24.05. 2019 10:40
G'day Roger.
I'm also backing the layshaft bush.
I use Nulon Smooth Shift https://tinyurl.com/y4secgo7 in my gearbox's, BSA's, cars and trucks.
The A7SS box was untouched after 9 years of racing (flat changes, no clutch).
Cheers
Title: Re: Gearbox protection
Post by: RogerSB on 24.05. 2019 11:31
Many thanks for all your valuable responses.

Most of my riding is over hilly Dartmoor on narrow, winding, up and down roads with lots of throttle, braking and gearbox work and it's at these times I notice it. On a fairly straight road with a steady throttle opening it isn't noticeable. It’s not an obvious loud clattering or knocking but more a change of sound and (I think) mainly when I throttle down. Gear selection, including neutral is easy and fairly smooth. I've been aware of this slight change in sound for some time now and I've been trying hard to detect where it's actually coming from and when (or if) I can do that I can investigate it.  My ‘hope’ (and I’m emphasizing hope here) is that a gear additive which coats the metal parts may be a quick and easy way just to confirm whether it is from the gearbox – not to hide the problem.

In the past when I restored and drove classic cars and used them as everyday transport (i.e. Austin Devon, Ford Prefect E93A, Rover 100 P4, Hillman Minx, Morris 1000 and a couple of S1 Land Rovers) when I rebuilt all the engines and some of the gearboxes I always added Wynn’s to the engine oil and, if I remember correctly, it was Slick to the gearboxes in the hope it would help to prevent wear and I was wondering if anyone on here has had any positive, or otherwise, experience with using these anti-wear additives in our BSAs.
Title: Re: Gearbox protection
Post by: Swarfcut on 24.05. 2019 16:48
Roger.. Years ago I bought some Snake Oil called Active 8 from a guy at the Stafford Show. This was demonstrated as  friction reducing oil additive and was demonstrated by applying increasing pressure to a steel slug against a rotating shaft. Needless to say the product offered the highest degree of protection against seizure. 

 I put it in my old Vauxhall Astra with 40K on the dial. It is now on 162000 Miles, still on the original camshaft. Regular oil changes and Active 8 top ups as required. The cams were notorious for wearing, so I reckon the product did some good, maybe, or was it down to regular oil changes with ever improving oils, driving style, mechanical sympathy, faith, hope, charity, e.t.c. Who knows?

 The pundits slagged it off, as being old WW2 technology, with a tendency to dissolve phosphor bronze, so I never had the courage to put it in the old bike.

  If you believe the formulation of any commercial lubricant is a delicate balance of the finest additives known, dumping a dollop of snake oil into your pride and joy seems a bit of a gamble. Like me I suspect we all believe in the Miracle in a Bottle, but the small print will usually disclaim the perceived lack any benefit as being beyond the maker's control. The only Guarantee is that these products will comprehensively empty your wallet.

 Swarfy.
Title: Re: Gearbox protection
Post by: RogerSB on 24.05. 2019 19:20
I can see your point Swarfy, my idea was to only use it as a one off just to see if the noise disappears, if it does it'll confirm it's the gearbox and then I'll know what I have to do.

It seems the benefits or not of MolySlip has been discussed on here before, way back in 2009 by Mike Hutchings of Dynamo Regulators. I came across it when doing a Google search on MolySlip.

https://www.a7a10.net/forum/index.php?topic=1075.msg7357#msg7357

According to Mike (in his reply no. 14) he said there was an amazing improvement, so I may pluck up courage and add some tomorrow and then go for a run before putting my bike up on its work platform next week to carry out a planned overhaul of the front forks.
Title: Re: Gearbox protection
Post by: ironhead on 25.05. 2019 07:39
I can see your point Swarfy, my idea was to only use it as a one off just to see if the noise disappears, if it does it'll confirm it's the gearbox and then I'll know what I have to do.

It seems the benefits or not of MolySlip has been discussed on here before, way back in 2009 by Mike Hutchings of Dynamo Regulators. I came across it when doing a Google search on MolySlip.

https://www.a7a10.net/forum/index.php?topic=1075.msg7357#msg7357

According to Mike (in his reply no. 14) he said there was an amazing improvement, so I may pluck up courage and add some tomorrow and then go for a run before putting my bike up on its work platform next week to carry out a planned overhaul of the front forks.



While its up on the work platform it would only take a couple of hours to strip the gearbox. Worth every second for piece of mind. A blown gearbox is no fun on the side of the road. IMHO. Put what the snake oil would cost into bronze.
Title: Re: Gearbox protection
Post by: Plammimam on 25.05. 2019 09:53
My view is if you do not know the history of the box and you suspect it might be the cause of your noise, strip it and look. Your time is by far cheaper than a wrecked box. I am building one now and it’s a simple box. With bushes at around £20 each you can replace most of the likely items for not a lot of cost. You then will have peace of mind where you can use normal modern oils and forget the additives.
Title: Re: Gearbox protection
Post by: RogerSB on 25.05. 2019 11:41
Many thanks again for the latest comments - I know what you're all saying makes sense.

When I can eventually identify where this change of sound I'm hearing is coming from then I'll be able to tackle the job properly. Bear in mind I only detect it when I'm actually riding and then its intermittent and only in certain circumstances - so not that easy to pin point. I've had the bike for a few years now with no serious problems and since fitting SRM's 4 spring clutch the gear selection etc is easy and smooth and I can't hear anything unusual when going through the gears with the engine running and the bike on the main stand.

Everybody seems to think my intention is to add an additive in the hope it'll cure a known problem with the gearbox. I'm not, as I'm not that sure it is the gearbox, I just think it could be because of the circumstances in which I hear it.

I'd like to emphasise again that I wasn't thinking about an additive as a miracle cure but just as a test to see if it made the slightest of difference - and if (by a miracle) it did - then I'll know exactly where I need to look, than I can plan to strip it down. What I want to avoid is stripping the gearbox and clutch etc unnecessarily, especially in the riding season  *sad2*.

(Edit): Also I don't believe a modern additive designed today for specific use in a manual gearbox will do any harm (ok, may not do any good either) but for a tenner it's not a big deal.