I had this clean 1972 R75/5 Transmission stored away and have decided to install it behind the R100S sidecar engine. Bob Clement, owner of Bob's Motorwerks, is in the process of rebuilding it and also a spare 1974 Five Speed I had sitting. The 74 five speed transmission has the kick start. That is the same model transmission I'm using in the sidecar now. The 4 speed is a more "robust" design and Bob recommends it for the sidecar.
Bob Clement with his Gold Wing sidecar
I'm currently running a 32/10 final drive with the 5 speed, but that might be a bit high geared for the 4 speed. I also have a 37/11 final drive which is one range lower geared so can swap if wanted.
I've noticed that my rear wheel appears to have a bit of a left "lean" so think the swing arm is probably "tweaked" a bit. Tire wear is normal, handling is not affected so I haven't bothered to do anything about it. Since I'm changing out the transmission, I'll swap out the swing arm with a heavier, later model LWB one I have.
Lastly, I may pick up a pair of matched replacement pistons / cylinders (currently on EBay) to have on hand if needed. The cylinder heads were redone, with new valves / seats / guides a few years ago so should be good for a while yet. I do have a loose pushrod tube on a left cylinder, although it is not leaking, the pushrod tube seal collar is loose and doesn't properly compress the seal to the engine block. I put a couple of hose clamps on the tube collar a couple years ago as a stop gap fix.
So this Winter I will separate the sidecar and go over (at least) the following....Transmission change, inspect clutch (only a couple years old / maybe 10,000 miles on it), change out swing arm, check and /or replace swing arm bearings, possibly swap out Final Drive, reseal oil pan & cooler which have been leaking, replace pushrod tube seals, new tires, and go over all ignition system components.
As the bike sits now, I would not take off on a multi thousand mile trip as I know the Transmission is tired. Although it still works fine and shifts well, I know its' days are numbered.
Bob works quickly so should have transmissions back in a week or two. His fees are reasonable:
$350.00 Labor + parts for the 5 speed and $450.00 Labor + parts for the 4 speed. So, barring any major parts needs, I should have both redone for under $1200.00, which I think is reasonable.
Old bike line up in Bob's Shop a few years ago: