TK5 Fifth gear does nothing

[jtrain199]

I recently installed a Toyo Koygo TK5 transmission into my 1984 B2. Everything shifts smoothly except for fifth gear, which acts like neutral. I tested the transmission before installation and all gears worked correctly. Any ideas on why fifth gear isn't engaging?

 

[19Walt93]

Some of the 80's 5 speeds had small reverse teeth like those a syncro would slide over but they weren't syncronized. If people slammed them into reverse without either engaging a forward gear first or waiting for the gears to stop spinning it would strip off the teeth and 5th became a neutral position. That doesn't sound like your problem since you had 5th when you bench tested it. Pull the drain plug and see if little steel teeth come out with the fluid. It seemed to me that the Mitsubishi transmissions had the reverse failures and the Toyos were prone to rear bearing failures that would whine in all but 4th gear.
Is it possible to install the shifter out of position so it can't fully engage reverse? That would be quick and easy to check.