[Formulajones]

Is it a short bed or single cab?

My understanding from our local driveline shop is it's the length of the driveshaft needed that determines the material, and if it's a long shaft and made of steel, there is a certain point where a carrier bearing is needed so the shaft can be made in 2 shorter pieces. Really long steel shafts aren't a good idea, They get too heavy and as mentioned critical speed becomes an issue, earlier I mentioned they start whipping if too long and heavy.

Think "jump rope"

Aluminum is lighter and will have a much higher critical speed before that occurs. So in some cases when the factory didn't want to use a carrier bearing to make a 2 piece steel shaft for what ever reason, they would use aluminum, make it one long shaft and done.