R1100GS Novice Gearbox Repair Attempt (with pics)

My mates R1100GS has been making a bloody racket for a while, like a light grinding noise at low speed. Lots of metallic flake / sludge on the gearbox drain plug magnet, oil only changed 2 months ago. Not having the cash for a pro rebuild, we decided that I would order the bearings and seals and have a go, with the understanding that if i break it, i wont be liable for the replacement cost.

Thought it may be of use to document it here as I go, success or failure, for anyone else that finds themselves in a similar situation.

Its not the first time i've pulled a gearbox on these so progress was pretty quick to start with. Two hours yesterday saw the box out and on the bench. The FD and driveshaft all appear to be fine and smooth, and there is a definite roughness when spinning the input shaft. Splines look good, no oil on the clutch disc and a fair bit of meat still. Will give him the option of putting a new clutch in, I would at this point if it was my own, but funds will likely decide.






I couldnt get the exhaust off on my own and didn’t want to jiggle it too much on the ramp. Looked like i could get the box out with the exhaust still in place so i did.

Heated the top cover with map torch, a bit of persuasion with a rubber mallet and it pops off.



There are shims on 2 of the shafts, carefully set aside for reassembly. Hoping that I wont need to measure and reshim as same shafts are just going back in.

Had to call it a day at that, Tuesday evening ill take the internals out and see if I can find the knackered bearing. Suspect it is (at least) the rear input shaft one that's disintegrated.

Well I have been reliably informed that I *am* going to have to measure and shim after all. I have a dial indicator, but have never used one. Was considering 'plastigauge' strips, anyone used these? I shall consult the clymer later, assuming I will find the required shaft tolerances in there...

Also should've removed the final rather than leave it attached to the swingarm as you'll need to remove it to fit the shaft as it's far easier removing it while still attached to the bike rather than attached to a loose swingarm

the voice of sense i realised afterwards that i should have cracked the torque on the pins before removing it. ill reattach it without the driveshaft temporarily so i can remove the final drive pins, thanks.

thanks for posting Gog
you might end up with more "friends"needing help
hope your touring plans are going well

Managed to get a bit of time in the garage lastnight. Having never taken a gearbox (of any description) apart before, I found it a little fiddly to work out the sequence of part removal What I did was:

Remove and label shims. Mine had one on the input shaft and one on the intermediate shaft.
Locate the little spring and ball bearing that sits on top of selector drum, put somewhere safe. Mine had fallen in to the box upon removal.
Remove gear and neutral switches, behind those there is a little circlip that needs removed from the keyed shaft on the end of the selector drum
Remove the gear lever from the splined end of the shift shaft (outside of the box)
Remove the large metal baffle plate, just lifts out
Remove the small metal baffle plate, needs 2 screws undone from outside of the box
Remove selector fork pivot shafts (2), these just wiggle out, leaving the forks in place
Swing the 3 forks away from the selector drum, remove the selector drum and shift shaft from the box. I gave them a wiggle and gentle tap from the other end and they popped out without any trouble. There is a washer at the rear end of the shift shaft that stayed in the box when i removed the shaft, luckily it was spotted and put back on the shaft before being lost forever. The selector drum also has 4 thin spindle things that can fall out, careful here.
This leaves space now for the selector forks to be removed from the gear shafts. Labelled and put aside.
Should now just be left with the three shafts in the gearbox
Turn box over and heat the rear bearing seats, I used an IR thermometer and about 110 degrees C.
Turn over again and use 3 of your hands to coax the shafts out of the box together, while your 4th hand holds the box on the bench. They came out without too much drama.








The culprit for the noise in the box is evident. Rear input shaft bearing is destroyed. The gear behind it has also been eating away at it, gouging the oil shield of the bearing. I have read on advrider IIRC about this happening on M97 boxes but not M94. Apparently some have machined a thrush washer to stop this happening, but that's beyond me just now so its going back together as is with a new bearing.








I used a cheap ebay gear puller (https://www.ebay.co.uk/itm/201908737706) to remove the old bearings, heating the bearing up first. Worked a treat. Waited for the shaft to cool, heated the new bearing and drifted on to the shaft. No trouble here as long as the shaft is cold and the bearing is hot. Repeat for all three shafts. On the rear of the input shaft there is a circlip, a split washer (sits in a groove) and a shield washer that sits over the split one. These need removed before you can remove the bearing, and refitted after new bearing is on.

Front input shaft seal drifted out with a suitable size socket, noting install depth beforehand. Drift new seal in to same depth. I'm using BMW seals from motorworks.

Cleaned the gearbox covers thoroughly with paraffin ready for reassembly. Bearing seats cleaned and inspected, no issues or damage at all here thankfully.

Ran out of time, so next session will be replacing the other seals and refitting the shafts. Got to work out if the old shims are still correct and then button it all back up.

That's going to need a bloody good clean out inside as well or you'll be back where you started. Cleanliness is next to godliness when it comes to gearboxes (or any internals for that matter).

Its all clean now Nin, I just didnt take any pics after cleaning

Not that much of a novice then


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It might be worth fitting a Touratech ‘hard part’ for the rear horizontal gearbox mounting bolt to reinforce it on rebuild, assuming you can still get them?.

A known weak spot, I had to get our coded TIG welder to repair a guys 1100 gearbox that had split the mounting lug clean in two after hitting a pothole in the dark.


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Pukmeister said:

It might be worth fitting a Touratech ‘hard part’ for the rear horizontal gearbox mounting bolt to reinforce it on rebuild, assuming you can still get them?.

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Mikeyboy has a load ...

Hard parts already fitted to this bike, and my own too. Cheers

I normally leave the seals out until reassembled,it makes checking for any binding on the shafts easier.
BUT ,remember to fit the rear input seal 1st as this fits from inside the box.

Great work Gog - thanks for all the pics & good luck reassembling.


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thanks mike - i’ll bear that tip in mind for next one, front input shaft seal is already in this time. to be honest i was hoping you or another pro that has done these many times before would read the thread and tell me if i had done anything wrong

cheers

gog said:

i was hoping you or another pro that has done these many times before would read the thread and tell me if i had done anything wrong

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in the interest of clarity i have already received some good advice and pointers from DrFarkoff in PM

Voyager is another who has good gearbox experience and not too far away from yourself...

ive heard of him mike but never met or talked. believe he isn’t too far but going to try and complete the mission solo

Good job

was good to meet you, however briefly it was, at dent