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drpetemurray
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VBMWMO #8864
Joined: 02/06/2015
Posts: 3

I am planning on rebuilding my /5 transmission .The tranny was working normal . The input shaft spline is toasty ,My plan is to replace the input shaft ,transmission bearings and seals. Is there any black majic involved ? My local dealer says 10 hours of labor Grief ?
What do those say who have done this ?

Thanks

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PeteM
Stroudsburg,Pa
73 R75/5 , 1014 RTW, IBA 359

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6546
Pete - Haven't done it and

Pete -

Haven't done it and for me, this is way outside my comfort zone. But, to each his own. Yes, I would say there's some black magic. It's critical that you get the shafts and bearings shimmed right. It takes specialized measurements in order to be sure there's not too much or too little play in everything. Then there's the issue with what to replace. What about considering the shifting forks or the dogs that are inside the transmission? I believe parts for the 4-speed transmissions are no longer available. In addition, there's the $2 part that can fail...that should be replaced with a newer shift kit...which I don't believe is available as a kit but parts have to be purchased separately.

There are some places to look out there...maybe they will help:

http://www.ukgser.com/forums/showthread.php/271570-Airhead-Gearboxes
http://jhau.maliwi.de/mot/gearbox.html

Good luck.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

drpetemurray
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Joined: 02/06/2015
Posts: 3
Thanks Kurt, The procedure

Thanks Kurt,

The procedure does not appear difficult regarding transmission shaft bearing preload and shifter fork alignment. If I have any doubt regarding those procedures the BMW shop can double check my work before cover install. I was using the Clymer manual.

Pete

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PeteM
Stroudsburg,Pa
73 R75/5 , 1014 RTW, IBA 359

pokie
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Joined: 02/08/2015
Posts: 86
Transmission shimming

Not so much "pre load" as restricting the end float. Pre load here will cause the bearings to suffer. What you are trying to achieve is zero end float.

Too much end float will cause a myriad of other problems, one being "savage clutch". Savage clutch happens when there is too much end float, so much that the shafts can move back and forth in the case (and it doesn't take much). When the bike is cold, the clutch works just fine, the situation rears it's ugly head when the bike heats up. The transmission case heats up and allows the bearings to move in the case, so when you are slowing down for a stop the shafts move to one end then when you start to let the clutch out, the shaft (or shafts) slip to the other end of the case causing the bike to leap forward, almost knocking the rider out of control.

If you've never taken a four speed apart before, a good tool to have (besides the holding tool and puller for the rear flange) is a digital camera to record your steps and what order parts go in. A simple thing like putting any of the washers back on the shafts backwards will cause problems. Don't force anything and use heat.

Go slow and methodical and you should be ok. Shimming can be a bit fussy but with a good pair of parallels, a caliper with a step function and a simple calculator, you'll do fine.

drpetemurray
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Thanks Pokie, I plan to

Thanks Pokie,
I plan to order the output shaft holder from cycle works to verify fork alignment.

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PeteM
Stroudsburg,Pa
73 R75/5 , 1014 RTW, IBA 359

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