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GS transmission guru fitment question

happy wanderer

happy wanderer

Day Dreaming ...
I've come across a rebuilt transmission from an '87 R100 GS. Not being familiar with what it might fit I looked at the MAX fiche and the part number is different from my 81 R80G/S and my 82 R100RS.

Sometimes these part numbers can be misleading and it is possible to use substitute parts. My question is whether it's at all possible the R100GS five speed might actually fit either of my bikes?
 
Not really a tranny guru, but I checked my notes which say that '81-on gearboxes are interchangeable. '74-80 gearboxes are interchangeable...not sure about the early 4-speed ones.
 
I'm no tranny expert either, but I think the only difference between the post 81 tranny's in the GS's with the paralever driveshaft is that the output shaft seal on the rear case is installed backwards and the vent hole plugged up. I'm not 100% sure what seal is called, but that one needs to be replaced for use in non paralever driveshafts. Hopefully the experts will come by and be more specific.
 
For the Paralever bikes, there is a different output shaft seal (which gets installed with the lip facing inward) and the triangular notch in the cover at the top of the seal is blocked off with some kind of sealant.

You can use that GS transmission in a non-Paralever '81-on bike if you just pull out the chunk of sealant. Most likely you could just leave the brown seal in place, but the green one is correct for a wet driveshaft.
 
AntonLargiader said:
For the Paralever bikes, there is a different output shaft seal (which gets installed with the lip facing inward) and the triangular notch in the cover at the top of the seal is blocked off with some kind of sealant.

You can use that GS transmission in a non-Paralever '81-on bike if you just pull out the chunk of sealant. Most likely you could just leave the brown seal in place, but the green one is correct for a wet driveshaft.
Click to expand...

Thanks very much for your reply Anton. I'm going to jump on that rebuilt spare gearbox. Fact that it would fit both my bikes is a nice bonus as I would have a bolt on spare ready while the original was rebuilt and too good to pass up!
 
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