Transmission name.......? What trans do I have?

I'm pretty familiar with GM automatics and their designations,
th400
th350
2004r
700r4
4l60e
4l80e
powerglide
turboglide

and the only manual I know the name of is the borg t56(f bodies) and t5(not even sure if thats GM though)

My question is this, what are manual transmssion designations for our large trucks.

My shifter is says low(i think) 1, 2, 3, OD, and R. So I guess technically its a 3 speed with granny low and overdrive. But to me its just a 5 speed.

Anyway my truck is a 93 3500, originally with a diesel. What tranny do I have?

Thanks everybody

mg5 or mw3 are the RPO codes

if i am remebering right the mw3 is the one with the "granny gear" LOW-4 which is the heavy duty one...

the mg5 is 1-5 like what is in the half tons

Good stuff, thanks for the info, I just need to figure out which adapter plate I'm going to need for my cummins swap