Monoshock Gearbox

[deckes01]

I have an '86 R65 with 39K on the clock. After a 400+ mile ride last weekend (the longest day on this bike by far, in the last few years) I noticed some clatter when in 3rd gear. The bike is shifting smoothly, and the noise is only on acceleration. Gear oil change revealed no obvious issues. I am not terrribly excited about doing a tranny re-build at home,(never attempted one) but after my local BMW dealership said that I could be looking @ about $2,000 in repairs, depending on what's up... I know of an '81 gearbox from a R100 available, but I'm curious as to what other boxes would work on my bike????

[jdiaz]

$2000? I don't think so. Fix the one you have so you don't have to worry about buying someone else's crap.

My '86 R65 had an issue with the output shaft which caused a slight vibration that could not be tuned out. The trans came out, a new output shaft, bearings, and re-shimming took place, and now that transmission shifts like butter. I think we spent $1000, and that included loaning me a spare to ride around with for a month.

You want to be looking up guys like Tom Cutter on IBMWR, Jim Barron in Woodstock, IL, or Gunther in southern Indiana (check the /5 webpage?). Jim Barron did the trans in my R65, and it is wonderful.

[flash412]

know of an '81 gearbox from a R100 available, but I'm curious as to what other boxes would work on my bike?Any airhead gearbox from '81 on will drop right in.

[kbasa]

Any airhead gearbox from '81 on will drop right in.

The internals, right?

[deckes01]

Jon,

Thanks for the advice, I am going to look these guys up to get some information on what to do. It sounds like your problems were a bit different from what I am experiencing. Based only on sound, I would suspect that I have a few teeth missing on 3rd gear itself, as the clatter is only heard while in 3rd. I'm just a little nervous about getting in way over my head on this one.
Thanks,
Steve

[AntonLargiader]

The internals, right?
The case and all, except that the output shaft is sealed differently for Paralever bikes. But changing that is a quick job for a mechanic with the right tools.

A bearing replacement/reseal/reshim is about $600 to $700 if no parts are broken.

[AntonLargiader]

Based only on sound, I would suspect that I have a few teeth missing on 3rd gear itself
That's really unlikely. You'd be tearing things apart if that were the case, and chunks of metal would be in the gear oil.

First, make sure your engine is tuned. Vibrations from mismatched cylinders can create clatter in the clutch and tranny. If you think you have a problem, drain the transmission oil and see if there's a lot of metal debris in it. If not, pull the tranny and inspect the splines.

[PHMarvin]

Hi, Dave,
No, NOT just the internals. If he has an '86, any twin-shock or monolever gearbox from the R45 through R100RT will fit. They are all basically the same, save any running changes. I'm not as sure of the G/S and GS models, but I think they will interchange, too. There might be an issue of the vent (at the gearbox output flange) being plugged. Ask Anton or Tom Cutter about this.

[28796]

While the tranny is apart make sure to get the circlip mod done so you don't have to go back in there again. At 34K the bearings were going away in my 87 R80 tranny due to the shaft moving.