I know how many I have but it isn't what the part store calls for. I have a 79 F250 4x4. My front and back shafts each have two joints. Parts store says they should both have three. I have even looked up and have seen where I am supposed to have 3. Has someone along the line replaced drive shafts in my truck. I first noticed this when I changed the front u joints in the front shaft and was given the wrong sizes from the parts store.

 

Two different types of drive shafts: Single Carden (left) & Double Carden (right). U-joint is basic part number 4635

Which type does your truck have?

 

2 ujoints at one end is a double cardan joint (although most people call it a constant velocity joint).

There seems to be a slew of different u-joints used over the years and previous owners could have swapped stuff out. Just take your drive shaft with you to compare in the shop to find the right ones. I think the trucks were 1350 size but maybe even smaller?

I wouldn't always trust the book on driveshafts.

 

1978/79 F250 4WD's (C6 & 4 M/T) used 1330's, but there are two different versions (Ford: C3AZ-4635-H & C4SZ-4635-A).

The OP should take all his old joints to the parts store to match 'em up.

 

2x with tabascom. Owners often and do modify these rigs and after 30+ years almost anything is possible.

Call me crazy but I would crawl underneath the truck and count 'em ... regardless of what the parts monkey behind the parts counter says his/her computer or books states.

 

X2 on get under there and look at them and measure the end caps (width) to get the size you need.

tabascom16 is right, rear d/s should have 2, one on the front end, and one rear rear. And you should have a slip joint/spline joint too on the end closest to the xfer case.

If things are stock the front d/s should have 3 one on the front. 1 on the (axle end) and 2 in the cardan joint akd CVC joint (on the transfer case connection point) .

And you should have a slip joint on the front d/s also.