Why do different trucks have different driveshafts? alum, vs steel? i can think of 5 different trucks and none follow a pattern of alum or steel. why is that?

Good question, I have no idea. I assume it has to do with length? Noise? I know that the big aluminum shafts have foam inside them.

what i know it that they can't make long steel shafts for what reason i don't know. that i why they make them out of aluminum.

Cars and trucks used to have long steel drive shafts, so making long driveshafts out of steel is not a problem. Aluminum is a lot lighter though, and lighter means better economy.

A common one piece steel shaft can't go over 70".

A common one piece steel shaft can't go over 70".

What are you basing that on? Ford F150 shafts use to be 77 or 78 inches long. I don't know what they are now.

A common one piece steel shaft can't go over 70".

the long bed crew cabs have a small shaft under the cab then to a u joint in a rubber boot then goes to a longer shaft down to the rear end. I know one long bed 4d dually like that, and one 4d long bed srw that i knnow was steel but not sure on if it had a small and a big shaft