Hi Slakewell -- the part I'm lookin at is described as a:
PENTON KTM 1975-1978 400 MC TRANSMISSION TRANS AHRMA 76 77 6SP MINT
I did a search on the Penton Owners Group site and found the following posts -- so it looks like it will all fit -- I'll probably go for it -- you can never have enough parts under the bench
Post 1 ...
Brian, the transmission gears and shift mechanisms will interchange between the '74-'77 250 and 400 motors. Not sure about the 175s. Black '73 motor had an old style, not so good shift drum. Somewhere around '75-'76 (Larry Perkins knows for sure) the side dogs on the gears were back-cut, ie they "locked" in after shifted together with the angle on the dogs. These gears in good shape shift together better and stick, much less popping out. Suspect you have worn side dogs with no back cut.
Good news is there are lots of good transmissions around, out of water-damaged cases. And splitting cases is real easy, and not much to jiggling gears in and out. I've bent a couple of the shift pawl arms back to the spec'd gap and they've worked fine. Get a decent set of gears out of a '76 or '77 and a spare center case gasket, and you can swap it out in a couple hours.
My old '73 Harescrambler was a shifting nightmare, but when I swapped in a complete '77 drum and tranny, it was sharp, snappy and perfect no-miss shifts...best shifting vintage bike I ever owned. Good luck with it.
Post 2 .....
Trannys in the silver motors are all the same. Check claw, shift fork straightness to it's shaft and dog edges on gears and you will prob find problem. However, I have a 72 175 engine I built that is doing this and I tore it down and checked everything and can find nothing wrong??? Im wondering if something may have been welded wrong as the old ones have welded shift drums. Dont have that issue on silver motors. At least your half way there now with the handling straightened out. Good Luck
