Speedometer question

[McC_65_91]

so i disconnected my non-working speedo cable the other day to try and narrow down the problem. disconnected from the transfer case (4X4) and the gauge, spun it and all good, kinda disappointing tho, already got a cable with my last big order, figured it was like $15 so might as well just order it, but now dont need it.

next i reconnected the cable to the T-case and started driving with it disconnected from gauge - cable not spinning... this would lead me to assume that it is the sending unit on the T-case right??

has anyone else done this on a 4x4? or know if the T-case sending unit on a 4x4 is the same sending unit on tranny on a 2wd?

all thoughts advice and help appreciated
PS its a 65 GMC, 4 speed