Gearbox whine in 3rd and 5th

[tr3ndy]

Hi Guys
I just joined the forum as I have got my eye on an r65 but need advice before I commit and join the bmw party.

The bike is a 1984 model (not monolever) and looks to be in good condition. The downside is the gearbox makes a loud whining noise in 3rd and a not so loud noise in 5th. I'm assuming this would be the bearings?

Bolting in another transmission sounds more fun than getting the original box rebuilt but like everything in Australia it's sometimes hard work sourcing parts. Do gearboxes from other bikes fit such as an r45 or r100 and if so from and to what year? I assume the k series is incompatible?

Thanks in advance for your help.

[Bob_Roller]

Both of my roadworthy R65's do the same thing, the '81 just had a transmission overhaul done 9,000 miles ago and still had the gear whine in third gear after the overhaul .

I've worked around jet aircraft for around 36 years, so my hearing is not great anymore, I don't notice any pronounced gear whine in fifth gear .

I've got 87,000 miles on the '81 and it has sounded the same since I got it .

One thing to check, if you can, is for water contamination of the transmission oil, if it has water in it, it looks like coffee with milk in it .

The water gets in by the rubber boot that covers up the speedometer drive cable where it enters the transmission .

If the boot looks deteriorated and not sealing well, good chance you have water in the transmission, pretty common problem .

You could use it as a 'bargaining tool' to negotiate a lower price .

Another quick things to look for, is gear oil dripping or on the rear wheel, quite common for o-rings to leak where the brake shaft goes through the final drive .

Take a good look at the brake master cylinder for leakage, quite common to get leakage here from a corroded and pitted cylinder bore, it's made from aluminum and if the brake fluid isn't flushed out regularly, damage happens here as well .

Malfunctioning odometer is another common problem, make sure it works, otherwise you may have a bike with unknown mileage .

The transmissions from the '81 model year, up to the end of the airhead series bikes, not quite sure when that was, but they are all interchangeable .

[tr3ndy]

Thanks for your advice. I'm going to see the bike tomorrow night so will see first hand how bad it is and will also check out the areas to check you have suggested.
It's also good to know that gearboxes from other models are interchangeable.

Fingers crossed its worth buying.

[steve hawkins]

All transmissions are the same for airheads, as long as you are mindful of the year.

I.e. an R100/R80 transmission will go into an R65 as long as they are from 1981-84.  It might well be that the mono transmissions are okay as well - infact I cannot think of any reason why not, but thewn I have never had a monolever.  The critical point was pre 1981 when they went from the heavy to the light flywheel.

It is the final drive when the gearing is changed.

[georgesgiralt]

Hello !
If you get the bike, I suggest you change ALL fluids including, of course, the tranny oil.
Remove the old oil in the gearbox, pour in 0.8 litre of Diesel fuel and run the bike for 10 miles. Remove the fuel and put a very good 80W140 gearbox oil in it. Run the bike for a thousand km and change oil again this time put the same gear oil you put  before. The noise could be vastly be reduced.
Otherwise, new bearings (and new gears locking springs...) could be a good investment.

[Barry]

Mine whines a little under load going up hill in 3rd but not in 5th.

5th has helical cut gears so it shouldn't whine. Got to think it could be a bearing on the way out.

All gearboxes have the same internal ratio's so if you can find an 81 on box from any other model airhead it should be fine.

[tvrla]

Take a look at the transmission drain plug magnet.

If there are slivers or chunks, the transmission needs work!

Soft fuzz is normal and acceptable.

You can access this magnet without draining the trans oil by removing the plug and quickly covering the hole with a finger.

Don't make the mistake of removing the engine sump plug, which is lower - the first one you see looking up.    

It's not normal for the transmission to have a loud whine in third and fifth. I'd be suspicious. A transmission from any 1981 to 1995 airhead will work.