BMW R35: new gearbox housing.

As I mentioned in my previous post, the gearbox with a hand operated gear switch lever is a cornerstone of the whole BMW R35 Restomod Project. Dismantling of the engine brought me no good news: even the gearbox case was extensively damaged. Here is how it looked after initial washing:

BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox caseExtensive oxidation and the wall of the battery compartment that was partially cut weren’t the main issues.  The main issues were as follows:

  • Most of the threads in  the case were damaged, drilled and tapped with larger threads. Some of the latter  threads were damaged as well.
  • The seat of the rear bearing likely seemed to be  loose, so to hold the bearing in place someone punched  the housing around it.
  • The rear contact surface of the gearbox was also extensively damaged by punching and using something like a chisel  as a main tool for parts separation.

Here are some illustrations.

BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox caseThe Inside of the gearbox housing did not avoid damage either. With such a list of damages it  was only wise to find another gearbox or at least its housing. However, it turned out to be quite a challenge. For long months I was searching locally and abroad, but it was all in vain. Gear boxes for R35 with a hand operated lever are very rare, and those that are worth buying are even more so. And then suddenly I came upon the most unbelievable:  transmission case that has never been installed on a motorcycle!  I wonder,  what is a chance to find 70 years old and intact NewOldStock gearbox housing? It was located in Germany and advertised only on local internet bulletin board.

Therefore I needed help to get that gearbox housing and I found it in Michael aka Scirocco, resident of KZRider.com web community. Many thanks to him, I got the gearbox housing at my disposal without any additional issues.

Here it is, the Holy Grail of our  BMW R35 Project. In the photos you may see it just as I received it: dusty from long storage. Precious vintage dust, one may say!:-)

BMW R35 transmission housing BMW R35 transmission housing BMW R35 transmission housing BMW R35 transmission housing BMW R35 transmission housing BMW R35 transmission housing BMW R35 transmission housing BMW R35 transmission housingI inspected it through and through and I found no traces of it ever being  installed on a motorcycle or that bearings and main components were ever installed in it.

BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox case BMW R35 gearbox caseHowever, I found out that the outsides of gearbox housing were media blasted some years ago. The traces of blasting are visible along the perimeter of the rear contact surface of the transmission case.

BMW R35 gearbox housing BMW R35 gearbox housingManufacturing markings:

BMW R35 gearbox housing BMW R35 gearbox housingAnd to finish the article, here are a few photos of gearbox housings in comparison. As you may see, the casting of the new box is more accurate. Also, housings have different part numbers: 235 209 111 01 for new housing and  235 209 111 00 for old. And here, again, I have to say that I am glad to work on restomod, where mixing parts from different modifications of BMW and even EMW R35 is acceptable and allowed.

BMW R35 gearboxes comparison BMW R35 gearboxes comparison BMW R35 gearbox housing BMW R35 gearbox housingIn the last two photos above one may see that in the new case holes for the  front unit of gearbox (housing that contains front bearing, front part of shaft and clutch lever)  are located  slightly askew. It may affect the position of the clutch release lever, but I think I already have ideas how to eliminate this effect.

 

 

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