i know absolutely nothing about 4wd ...

there's a 1990 f250 4wd extra cab long box diesel about 2 hours away that i am very interested in because it is the exact configuration i want and the price is right.

it has a broken drive shaft ... when i asked him which one, the guy didn't seem 100pct. sure, but he said it was the rear shaft.

can a 4wd be driven (highway all the way ... slowest speed i can reasonably get away with would be 50mph) with one or the other driveshafts broken ?

 

If it's the front driveshaft you can remove it completely and drive it as much as you want, as fast as you want.

If it's the rear you're probably out of luck. I think by '90 these trucks had a slip yoke at the rear of the transfer case. If that's true then removing the rear driveshaft would give you a 2.5" diameter hole in the back of the transfer case and all of the fluid would flow out.

If I'm wrong about the slip yoke being used in '90, then you can remove the rear driveshaft and drive it with the transfer case in 4WD and the front hubs locked. You can drive as fast as you want, but you may feel / hear some vibration at higher speeds (and may want to slow down if you do). the biggest annoyance will be that there can be quite a bit of vibration in tight corners. it won't hurt anything, but it's annoying. And keep in mind that the front driveline isn't as strong as the rear, so I wouldn't try to haul a lot that way.

 

If everything else is in good shape you avoid any tight maneuvering yea and it is not a slip joint for the rear driveshaft (believe it will be but may be wrong). That said 2 hours is a long way away driving a unknown back home though.

Myself I'd take your other truck rent a good size car trailer from someplace like uhaul and carry it home if I bought it. Tell them you're gonna haul a explorer or something, anything that is long but lighter than your tow vehicle. Otherwise they'll deny ya even though your 94 for example would have no trouble handling the job. The other option would be a dolly rear driveshaft removed broke or not.

 

If you are buying a truck from someone who says it has a broken driveshaft and can't tell you 100% for sure which one it is, then I would not be buying a truck from that person. I would immediately wonder if he even knew what he was talking about.

If you are determined then I would follow the advice given about towing it back. It could have problems with the 4WD system that he doesn't even know about.

 

Yea first thing came to mind reading the OP, I'd be concern what he was doing when the shaft broke......if that is what happen.

Hey a failed ujoint shaft fell out no biggie but he'd know which shaft it was. But doesn't know or just can't remember? yea right that's a tad hard to believe.

His not being able to recall suggest he may not know to start with, was trashing the truck off road or similar act and it broke down wouldn't move, so he walked away calling a tow.

Worth a look at for the right price but wouldn't be too confident about it being road worthy based on information provided thus far.

 

thanks for the input.
the truck is most definitely worth a look at the price he is asking, but i will drop the idea of trying to drive it home if i wind up buying it.
i am not concerned that he didn't know what he was talking about ... remember that not every truck owner is able to identify a water pump, even if they are holding one in their hands. these are the guys you can often get a good buy from when something breaks and the shop quotes them $1100.