we used four p80 12:1 Transmissions on our Linkage Drive. THe linkage involves stresses not normally seem in a drive train (there is some side load when the wheels switch, thankfully omni wheels make that minimal) and our transmissions held out fine, and still hold out fine! We had one problem with the drive shaft slipping, but that was our fault (we took that one apart and forgot to add the compression ring back on it
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I think these transmissions are awesome, they are so easy to mount, and for linkage drive, thats the most important thing!!
EDIT:
Here! This is the pic of our drive train and out mountings (notice the lack of support on the other side of the drive shaft, and it still ran fine!!