R100GS gearbox on 81 R80G/S

[dirtsurfer]

I am told the later gearbox is not compatible with the early G/S's . Can someone remind me what the difference is

[SteveD]

I thought they were compatible from 9/80 onwards? There were some internal changes like shift kit, gears were upgraded and the circlip was dropped for many years...
I'll be interested in the responses too.

fwiw a search with pn 23 00 1 338 461 on maxbmw fiche doesn't include 80-84 in the list of compatibilities.

Screenshot 2022-09-03 at 21-51-47 BMW Motorcycle Parts Search for parts.png (129.12 KiB) Viewed 829 times

[gspd]

I say they're interchangeable (until somebody proves me wrong).

[SteveD]

My search above looked at the later pn from the R100gs

This search is from the early R80g/s. from www.realoem.com because it gives a list instead of thumbnails.

fwiw...unsure if it helps though. The fiche has it's own idiosyncracies.

23002301786, 5-gear transmission
From: 04/02/1982 To: 05/24/2013 (ENDED)
Weight: 11.400 kg
Price: $2981.70
Supersedes: 23001242416 (09/01/1980 — 08/25/1988)

Part 23002301786 was found on the following vehicles:

R45-R65LS..78-85   (01/1978 — 07/1985)
R 60, R 75 , R 80, /7, RT (76-85)   (04/1977 — 01/1985)
R 65 GS, R 80 G/S, R 80 ST (80-92)   (05/1980 — 11/1992)
R 65, R 65 RT, R 80, R 80 RT (85-95)   (03/1984 — 12/1995)
R 100, /7, /T, CS, RS, RT, S (76-84)   (03/1976 — 11/1984)
R 100 RS, R 100 RT (87-95)   (07/1986 — 12/1995)

Copyright © RealOEM.com

However, Snowbum writes

Another problem to be considered is that Paralever bikes have different transmission mountings.

[gspd]

Another problem to be considered is that Paralever bikes have different transmission mountings.

Different transmission mountings?
Do you mean the 4 bolts that hold the trans to the engine?
Can you elaborate?
Or post a direct link to exactly what he's saying?
I can never find anything on his website without reading pages and pages and pages and pages and pages and pages and pages and pages and pages and pages and pages and pages and pages and pages of stuff.

[SteveD]

Another problem to be considered is that Paralever bikes have different transmission mountings.

Different transmission mountings?
Do you mean the 4 bolts that hold the trans to the engine? Unsure.
Can you elaborate? Nope, he doesn't. I'm gunna send Anton Largiader a question.
Or post a direct link to exactly what he's saying? way down the page a bit...https://bmwmotorcycletech.info/transmission.htm

I've done a bit of searching but no answer.

[dirtsurfer]

Thanks team. I really appreciate the responses (thus far). The reason I am asking is that I am looking at a used gearbox from an overseas ebay supplier; BMWSalvage in Germany. The the profile on the part states that it is from a '96 BMW R100 GS and is not compatible with R80 g/s.
Yet the description translates as:

"short input shaft, 5-speed, the output bearing has a detent in the bearing and the bearing should be replaced, comes from a running motorcycle with 58 TKM, housing no chips, input shaft runs well, not broken in, rear gearbox cover is not cracked, the speedometer is pictured not part of the auction !!, see photos for condition - please refer to the item description for more information. The condition is best seen in the photos"

My understanding is that the short input shaft is compatible with the '81 R80 G/S .

[Rob Frankham]

As far as I'm aware, the only difference between the two in terms of compatibility is that the monolever equipped bikes have the output oil seal on the gearbox set with the outside facing inwards while paralever equipped bikes have the output seal the other way round with the outside facing the drive shaft. The drive shaft breather (a groove ground in the gearbox cover casting where the oil seal seats) is also blocked with silicon.There are, of course, other variations that were applied over time to the 5 speed box but, as long as the box comes from a machine with the lightened clutch (Post MY '81) it will be compatible (apart from the oil seal as above).

Rob

[SteveD]

Yes Rob, I’ve just had a local airhead mastermind also confirm that it’s the output seal that is the difference. Cheers

[dirtsurfer]

Thanks all