BA Gearbox hints & tips

[simon.holyfield]

Chaps, I'm about to embark on the strip & rebuild of the Burman BA gearbox in my Square Four. I've read what Mr Waller has to say, and I have some downloaded Burman manuals, but I would like some advice from those who have gone before.

Is there anything I should be looking out for, any rebuild hints & tips, any key failure modes, any spares I should buy before I start?

[david.anderson]

Simes
When you dismantle the box there are 12 lose rollers around the gear selector shaft that are going to fall out, so when you remove the inner cover make sure you put the gearbox in a cardboard box to contain rather than loose those rollers all over the floor.
Dismantling is best done in neutral.
I have found the quickest wearing part is the layshaft bushes so they are worth checking.
Next check the sleeve gear bushes. If they are loose they will leak the grease oil mix, not good on a fresh rebuild. If you renew those bushes and rheem to fit, make sure the inner bush is grooved to feed some lubricant through to the outer bush as it can otherwise seize on the shaft and spin in the gear. The seal (for want of a better word) at the mainshaft is generally in good condition and may not need replacement but if it has hardened, should be replaced. Some people have the casing machined to fit a proper oil seal but it is not necessary if you are going to use the grease oil mix.
Next check the individual gear bushes as excessive play can lead to a whine, particularly in third gear.
Also check the mainshaft bearings. If the gearbox has sat for a period of time, condensation within the box can lead to pitting in the ball tracks so give them a good wash out with kero and inspect with a light for any pitting. the pitting is normally at ball contact point with the track.
Check your gearbox sprocket for wear and replace it if there is a hint of wear as it is a complete strip down again to replace it if you find it will need replacement in the near future.
On reassembly pack the 12 rollers into positon with grease and be careful not to dislodge them as you slide the inner cover on. Next the selector shaft and gear change quadrant must be timed so make sure you line up the centre punch marks on the two.
David

[chris.shearwood]

Hello Simon,
I suggest Loctite Bearing Retainer on the two sleeve gear bushes. I don't think I am the only one to have had the bushes slide along the mainshaft preventing 4th gear engagement or jamming the box in 3rd gear.
Regards, Chris

[simon.holyfield]

Thanks for all your help folks. It's now stripped & inspection is complete (and shown on the blog).

The ball bearings are shot; the bushes are on the upper limit of acceptability but the pinions, cam & forks are perfect.

What grease do you all use?

[simon.holyfield]

Any recommendations on grease brands, oils and what mixture I should use folks?

[Graham.Goral]

Spheerol (self-levelling) grease seems to be the ideal option these days, for those that don't want to bother mixing grease with oil. I've used it for a few years and it doesn't separate-out leaving dry grease in the box after the oil has eventually all seeped out.

[nevhunter]

Controlling end float and having good condition gear engagement "dogs" ensures the box doesn't jump out of gear. The selector forks can be worn and have play in the pins that move on the cam. The layshaft bushes should be the self lubing type unless the box runs oil. It might be difficult to get good bronze for that application. Nev

[john.nash]

Thanks for all your help folks. It's now stripped & inspection is complete (and shown on the blog).

The ball bearings are shot; the bushes are on the upper limit of acceptability but the pinions, cam & forks are perfect.

What grease do you all use?

Semi-fluid grease mixed with a little oil.
Mine is red. It comes in a gallon tin from the local place that mixes their own oils (they also do straight 40 for, I think, £43 for 20L - I need some more so I'll need to get down there for it)

[simon.holyfield]

Spheerol (self-levelling) grease seems to be the ideal option these days, for those that don't want to bother mixing grease with oil. I've used it for a few years and it doesn't separate-out leaving dry grease in the box after the oil has eventually all seeped out.

Thanks John & Graham. Any idea how much you need?

[dave.pitt]

Hi

I've got mine in bits too Simon. It's done 18 years and 28,000 miles since the last rebuild...
I use semi-fluid grease too. I used Penrite for many years but now use Morris oils for everything. British y'know!

In addition to what others have written I would say that the two bushes in the fourth gear didn't stick with Loctite when I used it 18 years ago! It's just my opinion but I think Loctite doesn't work when it's submerged in petrol or oily environments. I soaked my driving gear and new bushes in alcohol before assembly to get them clean. Perhaps they lasted awhile...

Check your selector forks, especially 4th gear... And do remove the split pins from the selectors and check the sliding dowels don't have flats on them in the slots in the camshaft.

The other thing I would say is on the timing of the quadrant and camshaft on reassembly. The book implies that you should rebuild in neutral and time the two 0's together. But this is NOT neutral... It is a false neutral between second and third gear. I annotated my Waller thus after scratching my head for awhile and finally thinking about it all. If you think that the quadrant moves up and down between 1st and 4th, then it's pretty obvious that the position of the 0's at half way along the teeth must be halfway around the camshafts rotation.

Going anticlockwise the 0 on the cam gear is at about 2 o'clock in 4th, 11 o'clock in 3rd, 8 o'clock in 2nd, between 5 & 6 in detented neutral, and about 4 o'clock in 1st. You can find an undetented neutral between 2nd and 3rd, and 3rd and 4th. The 0's align in undetented neutral between 2nd and 3rd.

And another thing... You will by now have discovered that the only way to change a gearbox (drive chain) sprocket on a BA box is to strip the whole box. Full marks to the designer! Burman got it better with the GB box... If your gearbox sprocket, an item prone to wear what with sloppy chains and road grit, looks even slightly dodgy, do yourself a big favour and put a new one on, rather than unnecessarily stripping the box for no other reason.