Transmission (innards) Notes

[wmax351]

I'm making this a section for notes relating to the (internals of the) transmission. Basically, deviations from the BMW and Haynes Shop Manuals.




1. The cover does not necessarily need heated to remove. Gently tap on the output shaft, and use large screwdrivers and fulcrums to remove it.


2. When removing the shift claw mechanism, the manual instructs you to remove the breather sleeve. This was not needed (and may not be readily possible) for my bike (A 1991). The rod which the shift claw rides on is slightly thinner than the inside of the breather sleeve. Simply pop the circlips off, and slide the rod out.


3. The seals are pretty straightforward. I was able to grab most of them with a hook type seal puller. Be careful that the point of the hook is on the seal, and not another surface.


4. The input shaft rear seal is a pain to remove. Its tiny, and really wedged in there. In addition, it is inserted in the reverse of normal lip seals. The usual prying surface is harder to reach.

[billday]

Thanks, Wmax, this reminds me how fervently I hope to get through my bricking life without taking apart a transmission.

[wmax351]

Thanks, Wmax, this reminds me how fervently I hope to get through my bricking life without taking apart a transmission.

If you get the chance, its actually fairly interesting, because it allows you to really see how it works (its not all voodoo). Not all that hard either. Only took me a couple hours to tear it down and clean it.

[billday]

Sure is pink in there...

[wmax351]

Sure is pink in there...

Pepto Bismol.


http://www.redlineoil.com/product.aspx?pid=44&pcid=8

[TimTyler]

So, how confusing is it to remove the transmission guts and put them all back properly?

I was scared to mess around too much when I tightened the grub screw last time I had the gearbox open.

[wmax351]

So, how confusing is it to remove the transmission guts and put them all back properly?

I was scared to mess around too much when I tightened the grub screw last time I had the gearbox open.

Really not a big deal at all. Where it gets hard is if you have to disassemble any of the shafts or replace bearings, because you have to re-shim the transmission. This requires a special tool and careful measurement. Alternatively, you can use some really straight bar-stock (I mean, really straight. Think instrument grade). 

[Justmike]

I was having some real difficulty getting accurate measurements for end-play. Any wobble at the end of each shaft would cause the measurement to vary. I had to find another way if I was going to have any confidence in the numbers.
So, the thought of Plastigauge crossed my mind, but since I didn’t have any, nor could I find any of the right size or quantity I had to consider something else.
Voila - lead solder! I dug through my boxes and found some that was 0.040” dia. - perfect since the gap I was going to measure without the shims in place was between 0.020” and 0.040”. I cut four little pieces about 1/4” long, located them radially on either side of the bearing bore and secured them in the cover bearing bores with some grease. I carefully installed the cover and torqued it in place, then removed the cover to find nicely “squished” pieces of solder. I then measured the thickness at the “squished” area, subtracted from this number the desired end-play clearance of 0.0019” - 0.0059”, and the result is the shim thickness required. I repeated this a few times just to confirm the measurement and found them to be very consistent.
One thing I found when measuring was that it is very important to measure from the face of the outer bearing race and not the end of the shaft! - the shaft is proud of the bearing races by a good few thousandths of an inch and measuring to this point will result in shims leaving too much end play.
I’d be interested to hear any comments or criticisms- I haven’t buttoned the transmission back up yet 😉

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[bocutter Ed]

I remember using solder to check the cylinder gaps on printing presses. That was in the '80s.