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monkeybikegirl
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VBMWMO #9267
Joined: 05/15/2017
Posts: 55

Hello everyone
My driveshaft to transmission bolts have come loose twice now under hard riding. First time I would not even have noticed but the drive shaft boot was leaking and when I replaced it there were two of the bolts and washers in the folds of the rubber boot and the other two were loose. I replaced the two beat up ones with new and used the washers from the old ones. I also used blue Loktite on them, but since the threats are all oily, I'm not sure if that works. Well they came out again. This time one came out completely and two were loose. Other then removing the transmission and cleaning the threats, can I make sure the bolts stay. I am assuming that the bolts might have done some damage to the shaft, as they were slightly beat up.
Thanks very much for any input.
Christian

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6866
You should not be using the

You should not be using the long bolts with split washers. There have been instances of them coming loose as you have experienced. They come loose because the washer breaks or become weaker and doesn't keep the tension on the head. BMW went to shorter bolts. When installed correctly with a goodly amount of torque (and a bit of blue Loctite), they should stay in place.

Get a set of new short bolts. See if the bolt threads will feed easily by fingers into each of the holes in the output flange of the transmission. If they do, then you're in good shape. If not, you might need to chase the threads to clean them up. To tighten them up, I use the closed end box wrench from the tool kit. I put a rag in my hand, step on the rear brake, and give the bolt a good grunt. There are special adapters to get a torque wrench into the tight space. It's supposed to be 29 ft-lbs. Be mindful of the extensions and how they could change the actual torque versus the torque shown on the dial/meter. Unless you do it right, the applied or actual torque will be higher than what the torque wrench displays.

__________________

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

monkeybikegirl
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VBMWMO #9267
Joined: 05/15/2017
Posts: 55
Thanks so much, Kurt.

Thanks so much, Kurt.

brownbmw
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VBMWMO #7491
So. Cal.
Joined: 01/03/2009
Posts: 92
BMW still offers the longer

BMW still offers the longer bolts and washers for early airheads, and the shorter ones (no washers) for the later models.
It's OK to retrofit the later short bolts (without washers) on the early models. You must use loctite on these.
Neither version of the drive shaft bolts should ever be re-used as they have one-time-use stretch threads.

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