Naughty Gearbox

[andrew.chapman]

Thanks David. That is really helpful.

I am in two minds about whether to repair the original box or swap it for my spare. Depending on the cost, I might do both. I am very curious to see what has been going on inside the box but I also want to minimise the time that the bike if off the road. I like to ride all year round.

[John.Newbury]

I have replaced all bearings and bushes in my GB gearbox and it still whines in 3rd gear, don't they all do that?

[nevhunter]

If you examine the particular gears that are meshing when the noise occurres you will inevitably find a line on the tooth profile where wear has taken place. It doesn't have to be much. When you build a gearbox up out of a "mixture' of gears, from various sources, sometimes they will not mesh perfectly and CAN occasionally get better with a bit of use, but don't get your hopes up too high, this doesn't happen very often. A noisy gear can indicate the hardness is coming off a tired gear and this may continue at an increased rate and this will contaminate the gearbox oil eventually. The gear that seems to wear the most is the one on the layshaft which meshes with the output gear, ( sometimes called a sleeve gear). as it does more work than any other in the box. Nev

[david.anderson]

If after replacing all bushes you still have a whine it can be reduced a bit by using the 50/ 50 oil grease mix that was used in the BA boxes. The oil grease mix will halve the noise and also reduce the oil leaks out of the box. I do admit that one of my GB boxes has a third gear whine. That box was in a very bad state when I got it and it whined in third from the rebuild. I stripped it again to check and the only tell tale sign is the fine line on the teeth that Nev referred to. I believe the wear on the teeth is as a result of sloppy bushes not being replaced in time.
David

[chris.vredenbregt]

Whining of gears has nothing to do with bad teeth the fact is that the shape is not optimal (straight) that's why modern gears are under an angle to have more surface where they meet.
Second point is that all the gears except the highest are only shortly engaged and get no time to run in.
The highest gear get smoother after a long time and therefore makes less noise.
I experienced that on several of my bikes , but grease helps anyway...chris

[brenton.roy]

Yes, but all the gears are straight cut, and not all gearboxes whine. Straight cut gears do whine a bit, but there must be other factors for third gear only noise.
Third is the gear that has had the most dropping back a cog up a hill, quick overtakes and slow traffic work.

[John.Newbury]

Only ever used matched gearsor originals in box and never found any wear lines very fine or not. I would suggest it's a function of the epicyclic profile and how well it was machined and matched and Chris is absolutely corect about modern gears. I just accept the characteristics of my old Burman gearboxes and enjoy their sounds provided it's not excessive there is no problem.

[david.anderson]

It is well known that helical cut gears are much quieter than straight cut gears. It is also well known that many Ariels have a third gear whine. I have discussed the third gear whine with older Arielists including a former dealer and a prominent racer. They have stated emphatically that the Burman box did not whine when new. I would be happy to hear from anyone who has actually experienced a 3rd gear whine from a new GB box.
I have rebuilt numerous different GB boxes in the past 20 years, mostly for others. Some of the boxes were in poor condition and after rebuild (new bushes included) the feedback that I have is that the boxes that had the badly worn bushes have a whine. I currently have 5 bikes fitted with GB boxes, 2 VH, 1 NH, 1 HT and a Mk2. The VH and NH boxes were in good condition when I got the bikes. The HT box was one that I made up from a Matchy AMC box and an Ariel box and the Ariel cluster which was in good condition was used (yes I know it is not wide ratio but it better suits my off road riding anyhow) None of those boxes have a whine.
The box in my Mk2 was however like the rest of that bike, severely neglected and in very bad order. I fitted new bushes and bearings throughout and have a whine in 3rd gear only and on reinspection there are minor wear marks on the teeth, just as Nev described. I can see no other reason for the whine. As I find the whine offensive I have used an oil grease mix to reduce the noise.
I believe a well serviced and maintained Burman box will do large mileages without becoming noisy. I purchased my first VH (which had been upgraded to HS Mk3) in 1972. At that time the bike had over 70,000 miles on the speedo and after tracing the original owner (who was a former employee of the Australian Ariel importer) I was advised that there was also a lot of race track miles done. Since that time I have done an additional 120,000+ miles on that bike, so the box has done about 200,000 miles. I have regularly checked oil level and have rebuilt the box a few times. I have replaced bushes as soon as a little wear develops which has kept the gears are in good order. There is no whine in 3rd gear or any other for that matter from that box.
That is my experience, yours may be different.
David

[p tuxworth]

now ive got to strip the gearbox on my ariel bitsa , 3rd gear whines and i was putting up with it ( for the last 32years ) now im worryed alls not well , apart from this whine the gear box is spot on and far better than my Triumph
http://s1205.photobucket.com/albums/bb4 ... kes038.jpg

[nevhunter]

Plenty of straight cut gears will run perfectly quietly provided they are made accurately, have not changed their profile due wear and the accuracy of their alignment has not altered. This means the bearings are sound, in practical terms.
A ball or roller bearing where the surface has gone rough due corrosion or fatigue pitting of its bearing surfaces, has occurred will make a noise also.
Third gear seems to be the main one to become noisy but the noise eminates often from the gear that is in constant mesh with the final drive gear on the end of the layshaft. ( The smallest one). This gear is very much the hardest working gear in the whole gearbox as it is always working unless you are in top gear. ( which is not a gear at all) Top gear is "one to one" and it is a situation where the mainshaft is locked directly to the output gear and all the gears in the gearbox are doing nothing but rotating with NO load on them
The "3rd gear whine" shows up most because that is the time when the layshaft is going at the fastest speed with load on it.( Remember it is in constant mesh with the final drive gear). ALL of the lower gears vary the engines torque and then feed it through this pair of gears, so they are the ones you should inspect. You can arrange all of the gears asssembled in the gearbox intermediate cover if you want to see their relationship.
Getting back to the original problem, the falling out of various gears happens when the engagement dogs become worn. Loose bushes allow the parts to "tilt" and wear more so they throw out of engagement under load. Not much can be done with the BA and CP gearboxes in this regard, to remachine these surfaces due to their design, but the GB, AMC and Norton boxes can have the engagement dogs reshaped with a tool and cutter grinder,( carefully) and make sure all the bronze bearings fit well. Nev