Transmission Swap Gone Wrong

[jared_larsen]

Hey there,
Truck: 79 Sierra 2500
Trans: TH400

Hey there, I just swapped out the original '79 tranny out for a "new to me" one and am not sure of the year it came out of. I didn't do the work I got a guy to come to it while I was away working, and he left the driveshaft off. So I'm underneath putting the driveshaft bak on and Im a half inch short to connect it at the tranny.
Am I crazy? Shouldn't it just fit right in? Those trannys should be same size no matter what year right? Does the drive shaft extend anywhere? Does the tranny shift up and down the frame? Do I need an extension of some sort?
Any advice? This is my first restoration and am learning as I go,

Thanks

[zieg85]

There are different lengths. 2 have the slip yoke and one the u-joint bolts directly to a yolk

[jared_larsen]

Hey, it's the two piece drive shaft with the yoke that bolts to the frame in the middle, does it slide apart somehow?

[zieg85]

OK, I re-read your post, 1/2 inch off isn't a big deal.  Your center piece is a carrier bearing and there is slots where it bolts to the frame cross member.  The drive shaft slip yoke should move 1/2 inch no problem.  It should slide easily when you loosen the carrier bearing holder bolts.  Not sure if it is the correct terminology in my description

[VileZambonie]

What transmission did you take out and what was the tailshaft length?