Cracked R1100GS Transmission Case

[MotorradMike]

MJ Gurunathan

You, sir, are altogether too calm, too reasonable, and too polite.
Nice guys finish last.
But they're still nice guys.

[ragtoplvr]

If the peice is broken out, and a crack does not extend into the case, a good welder should be able to build up the broken part, then drill out and tap.
Rod

[def]

Originally Posted by ragtoplvr

If the peice is broken out, and a crack does not extend into the case, a good welder should be able to build up the broken part, then drill out and tap.
Rod

Certainly worth a try...

BTW, I would hire someone to throw a brick thru the BM........never mind.

[Whale Rider]

If you want to try the welding path, I could send you that part of the gearbox housng only not the complete rear housing. I had a crash on my 1100 a few years ago and broke the left hand side out of the housng. I am working on a project at the moment and have cut the rear bell housing part off the gearbox to fit into a frame I am building. I do have a spare complete gearbox but I think freight costs between New Zealand and Singapore would be prohibative.
WR

[AntonLargiader]

To answer the underlying question: your transmission internals will fit into any other M94 case (obviously) without changes.

They will fit into an M97 case once you have upgraded the input shaft bearings and the rear intermediate shaft bearing.

They will not fit into an M93 case at all.

You can probably use your existing cover with any rear case, but the appearance will be different (M97 is thicker and has a different finish).

[TXjames]

Originally Posted by AntonLargiader

To answer the underlying question: your transmission internals will fit into any other M94 case (obviously) without changes.

They will fit into an M97 case once you have upgraded the input shaft bearings and the rear intermediate shaft bearing.

They will not fit into an M93 case at all.

You can probably use your existing cover with any rear case, but the appearance will be different (M97 is thicker and has a different finish).

They will also fit the M96 that I have with the use of what I think is called the "clean bearing kit" from BMW. It has a 3mm spacer to compensate for the greater depth of the taper bearing.

[MJ Gurunathan]

Hi all.


So I went back down to the dealership and asked them about the technician about what happened with the gearbox. I got pretty much the same answer as I did from the service rep; that the pin seized and as he applied leverage to remove it, the gearbox threads gave way. BUT he did produce a heat gun and tell me that he tried to heat the pin before removing it - which I think might be a bit too convenient, but there is no way that I can prove that he didn't.

One of the theories that he put forward was that the wrong type of thread locker was used when the pivot pin was put back in place, but I know that is rubbish because I used the same type of red loctite as specified in the manual. What I think happened was that he tried to loosen the pin, found it wouldn't budge, put a bit more force and *crrrack* there went the gearbox. Out came the heat gun and impact wrench and then miraculously the pin gets removed.

Let's see what I can do to sort this mess out but I can be sure of one thing: I'd rather sacrifice my own time and work on the bike myself, rather than send it in for repairs to the dealership. What a horrid experience.

Thanks all for the great advice!

[MJ Gurunathan]

OK once again thank you all for the great advice.

Special thanks to all who have volunteered help in one way or another with parts.

Here's what I've learnt so far, summarised for anyone who cares to read it. Of course, all of the information below has nothing to do with the R1100S transmission, which I know nothing about and in any case will not fit the R11000GS/R/RT.

Please correct me if I'm wrong, I'd like to try and get this all right so we can build up a reference of sorts.

1) Ratios:

The R1100R/RT/RS/GS M94/M97 transmissions all have the same gear ratios. The M93 transmission has different gear ratios from the M94/M97 transmissions.

Different final drives are used for different R bikes. The ratios are presented below:

R1100RS 31:11 (2.818)
R1100RT 32:11 (2.909)
R1100GS 33:11 (3.0)
R1100R 33:11 (3.0)
R850R 37:11 (3.364)
R850GS 37:11 (3.634)

2) Interchangeability (complete gearboxes):

All M94 and M97 gearboxes are interchangeable. M93 is interchangeable with M94/M97 but you'll get different ratios in the gearbox.

3) Interchangeability (internals):

M94 internals will fit M97 housings with modifications to input shaft and rear intermediate shaft bearings.

M97 internals will fit M94 housings with modifications to intermediate shaft bearings. Some M94s had the newer M97-type bearing here.

M94/97 internals WILL NOT fit an M93 housing.

4) Interchangeability (housings)

The M97 housing has thicker walls and a different finish so there will be some mismatch when the front case of an M94 transmission is bolted to the rear case of an M97 transmission. Opinion is that it is possible to mix and match M94/M97 cases.

There is no such thing as an M96 transmission.

Please add on as you see fit. I will try to refine this when I have more time.

Regards;
MJ.

[AntonLargiader]

Originally Posted by MJ Gurunathan

M97 internals will fit M94 housings with modifications to input shaft and rear intermediate shaft bearings (this is an assumption, can someone verify this?)

Only the intermediate shaft bearing*. You just have to use more shims on the input.

I am unsure as to what an M96 transmission is, could someone shed some light on that?

Doesn't exist.

* EDIT: in some cases. Some M94s had the newer M97-type bearing here.

[fallingoff]

hi here is a link to ebay http://www.ebay.com.au/itm/270984116...84.m1423.l2648
for 1100
bike is in syd oz

i have had cases welded in the past with success


i hope this helps

cheers

q

[TXjames]

Originally Posted by AntonLargiader

Doesn't exist.

True, true. Sorry about the confusion. I got my numbers mixed up. It is an M94 case out of a 1996 RT.

[rutard]

Originally Posted by MJ Gurunathan

The M97 housing has thicker walls and a different finish so there will be some mismatch when the front case of an M94 transmission is bolted to the rear case of an M97 transmission.

Does this mean that they can't be matched? Or is it just a cosmetic problem?

Thanks for the transmission synopsis!

[MJ Gurunathan]

Originally Posted by rutard

Does this mean that they can't be matched? Or is it just a cosmetic problem?

Thanks for the transmission synopsis!

I am not sure of this. Dimensionally the cases should be the same, but until and unless I have the cases in hand I cannot be certain.

Logically this should work. You've got the same swingarm, driveshaft, clutch, clutch bell housing, everything is the same... and if you can swap the gearbox as a complete assembly, surely you can swap housings. Personally I think it is best to keep them as a matched set.

Honestly if I had some money I would buy a used transmission, tear the bloody things apart and do a Lego on them. Haha! See what fits where using what in which way... whoaaaa....

[MJ Gurunathan]

Good day all.

I would like to share my experiences with all of you, so that I can help anyone who faces the same issues that I did. Sorry this update took so long, but my health hasn't been too good. Finally got the job done though!

Synopsis:

Motorcycle Model: 1994 R1100GS, M94 transmission.

1) Whilst removing the RHS pivot pin for the swingarm from the gearbox, excess force was applied to a seized pin. This caused the housing to crack as in this picture (cracked portion is circled below):


DSC03288-1 by MRF3343, on Flickr

Tips:
a) Use the correct threadlocker when installing the pin.
b) Heat the gearbox around the pin prior to removing it. The heat will soften the threadlocker and make it easier to remove the pin.
c) If the pin seizes, DO NOT FORCE THE PIN! Drill it out and carry out a thread repair using a wirethread insert.
d) Oversize holes can be repaired using a solid insert. Cracked holes must be welded, the case crack tested and then retapped.

2) The crack was caused by excess force that was applied to the swingarm pivot pin. The gearbox was stripped down to facilitate repair. Here are some pictures of the internals of the M94 gearbox:


IMG848 by MRF3343, on Flickr

And again:


IMG861 by MRF3343, on Flickr

Tip:
a) Take pictures as you carry out each step in the disassembly process.
b) Put all parts in plastic bags. Label them with the BMW part number.
c) Match spacers to shafts, bearings to races. These parts are already bedded in.

3) After the gearbox was stripped down, it was cleaned in a solvent bath and then plastic-blasted to remove all traces of the original coating. The gearbox cases were then placed in an oven set to 140 deg. C for about an hour. This was done to drive out any oil or solvents that remained in the porous aluminum. Once I was satisfied that the gearbox was clean and oil free, I handed it to the welder to start the welding process. Here are some pictures of the gearbox after cleaning and plastic blasting:


IMG925 by MRF3343, on Flickr

And another view:


IMG946 by MRF3343, on Flickr

Tips:
a) The paint on BMW gearboxes is very tough. To save time when blasting, soak painted parts in paint stripper to loosen the paint. You can then blast the paint off with some ease.
b) Use kerosene to clean the gearbox, then a solvent degreaser.
c) Heat parts in an oven to drive out oil and gases from the porous aluminum.
d) Plastic bead blast the gearbox casings. Plastic blasting is gentle and will not harm the parent metal. Accidentally blasting a bearing seat or gasket surface may damage it if you're using highly abrasive media like alu-oxide.

4) The gearbox is made of an aluminum alloy. Some form of inert-gas welding must be used when welding aluminum. In my case, I TIG (tungsten inert gas) welded the gearbox. The material was built up in small sections around the cracked area. Once the crack was built up, the threaded hole was built up to repair sections of thread that had chipped off. Buildup was continued until the hole diameter was less than 24mm. This is because the pin has an M27X1.5 thread; a 27.0mm-1.5mm = 25.5mm hole must be bored to allow the thread to be created. Below are pictures of the gearbox during the welding process.


IMG926 by MRF3343, on Flickr

And again:


IMG927 by MRF3343, on Flickr

After blending:


IMG944 by MRF3343, on Flickr

Tips:
1) Make sure the affected case is clean and free of oil, dirt and grease before welding. It is important to heat the part in an oven to drive out anything that may 'gas out' during the welding process. This can cause weld porosity.
2) It is a good idea to build up more material than is necessary. You can always machine the part to size later.
3) If possible, leave a small amount of undamaged thread to act as a hole center reference and as a guide when tapping the hole.
4) If possible, do not weld completely the flat surface next to the pivot pin hole. You will need a small portion of undamaged material to act as a datum to machine the face flat.

5) Once welding was complete, I started planning the machining of the affected area. To set the workpiece up correctly, I needed two datums; one to set the gearbox parallel to my machine table, the other to set the gearbox perpendicular to the table. I set the gearbox up on a milling machine as in the picture below:


IMG1177 by MRF3343, on Flickr

Here again is the setup:


IMG1178 by MRF3343, on Flickr

And another view:


IMG1181 by MRF3343, on Flickr

The centre of the hole was conveniently found to be related to the distance between centres of the footpeg mounting holes. A pin of the correct size was held in the machine spindle and the table adjusted so that the pin could slide easily into the footpeg mounting hole. I then used an edge finder to set the workpiece zero. This hole centre was confirmed by running a threaded rod into the pivot hole on the other side of the case and seeing if it would clamp neatly in the chuck of the milling machine. I also confirmed the hole centre distance from the mating face with the angle plate by comparing it with a measurement (previously taken) of the hole centre distance from datum of the pivot pin hole on the LHS of the gearbox.

I then bored the hole to 25.4mm ID (0.1mm allowance) by pocket milling. You can see the machine in action below:


IMG1183 by MRF3343, on Flickr

Sadly I had to de-rig the job as I had to start on another project. Not good practice because this meant that I lost the hole centre and would have to setup the job again (clocking the angle plate, finding hole centre etc) in order to accurately tap the hole.

Tips:
1) Again, make sure you leave some portion of the original hole undisturbed. This will help you find the hole centre much more easily.
2) Assemble all your tools before you start. It is best to machine and tap at one go. This will help you save time on workpiece setup later.
3) Check and recheck dimensions before starting machining to avoid expensive mistakes.

6) Once I had some free time, I headed down to the shop to start tapping the hole. I used a dial gauge to indicate hole center and then tapped the hole. The picture below shows how the tap was set up:


IMG1216 by MRF3343, on Flickr

Tips:
a) Make sure you have your hole center correct. Any misalignment might cause the swingarm to shift or the swingarm bearings to wear and will affect the driveshaft alignment as well.
b) Tap slowly. Make sure the tap is perpendicular to the workpiece.

That's it! Job done. I'll powder-coat the cases and then reassemble the gearbox when I have more time. I shall try to get bearing sizes and seal dimensions so that you won't have to go back to BMW to buy bearings and seals. Saves a great deal of money.

MJ.

[def]

I have always admired skilled welders and machinists...they understand how to fix things broken by those of us who are unskilled with tools or use the wrong technique when repairing things made of metal.

During the restoration of his 1970s vintage Triumph T100, my brother discovered one of the engine mount tabs on the crankcase was broken. A local welder repaired it without drama for a few bucks. To this day, the repaired case is fine.

Nice work on the transmission case.