R1100s transmission interchangeability

[san augustine]

Noob question, is it possible to use later transmissions, let’s say a 2004, in a 1999 bike? Just asking.

[908/930]

I did a quick look at the part numbers and they are the same.

[san augustine]

Thanks, was curious if they were interchangeable like airheads.

[908/930]

Only R1100s though, the other R1100's were 5 speeds, the 1150's likely share similar internal parts but case is different.

[Jozef Schumann]

There's a bit more to be gleaned here.

The gearboxes for our R1100S's differed from early to late units. ALL of the bikes manufactured prior to 2003 were fitted with the early boxes. The gearboxes can be identified by the suffix following the gearbox serial number located on the transmission housing adjacent to the timing hole port on the right side of the bike.

The early boxes will almost certainly have a 'GAB' or 'GAJ' following the number. However, this is not absolute as it can also be a 'GBB' or 'GBC' or others. For example, the lightweight bikes with black motors obviously had black gearboxes and those were coded differently.

____________________________________________

The late '03 onward production machines were fitted with improved gearboxes known as the EVO box. These had a narrower gearset assembly with a deeper tooth profile which shaved combined gearset weight from about 8.5 kg to 7.7.

BMW also improved the shift forks by employing teflon bushings - and the selector assembly itself was improved by increasing material thickness and modified ratcheting function. Though nothing can be found in any literature or engineering white papers available to the public, I am somewhat confident this was a production fix addressing complaints by teams and riders of these bikes when in an competitive setting, complaining of difficulties shifting, particularly at high revs. Having close to 19 pounds of metal rotating at constantly changing high speeds results in considerable internal loading. Missed or in any way bungled shifts is not only frustrating for the rider decaying confidence in his machine throughout an event, but also a deciding factor leading up to the finish line. I can only speculate how many motors tagged a piston via valve float resulting from a missed shift. Who knows. More than a few I'd wager.

I know I, personally can attest to the improved shifting performance when seriously exercising my bike. Surely, many of you have also noticed times where the gearboxes reluctance to change gear was usually when you were really hustling down your favourite route. That being said, with the early boxes, there is rarely an issue when riding in an normal manner, even spiritedly. I have found only fast gearchanges with the tach at, or nearing redline is where issues surface.

The late EVO variants will always have a suffix starting with a 'J'. i.e, "JAG, JAE, JAJ, JAS" etc.

I can assure you a new box from BMW will be an EVO.

These are very strong boxes with internals being identical to the 130 bhp K1200RS and GT's.

Actually, if one is mechanically capable. A straight swap of the internals into your undamaged case is absolutely do-able.

If you're used box hunting and you want the best box, the EVO is it. If you're not a hooligan, it won't benefit you in any way and a properly maintained early box is perfectly fine. Regardless of which box is chosen - the input shaft splines should be the very first thing you look at. If I were in need and came across an EVO and older box, the one with the good input shaft would get the nod without reservation.

Hope this helps and good luck.

J.S.

[njsax]

Good info, Jozef. Thanks!

[mgp steve]

Jozef, that is some cogent, concise and detailed info!

Do you know how to determine what number build of 300 a specific, plaque-less ‘04 BCR would be?

Thanks, Steve

[Jozef Schumann]

Hi Steve -
Forgive me for not responding in a more timely manner, I am immersed in more things than any one person should be.
I have been asked this by several owners in the past, even inquiring with some well trusted contacts overseas and have been unable to obtain this information.

Surely, one would assume such details would be held somewhere in BMW's Berlin databank. Why motorrad would be so cryptic in divulging this is anyones guess.

J.S.