Driveshafts

Combat_Medic · Post by **Combat_Medic** » November 2, 2007, 2:27 pm

The driveshaft on my f250 2wd is a 2-piece unit. I have also noticed one piece driveshafts in parts catalogs and such. I was wondering what the significance of this is. Are there benefits to having one or the other in a given performance envelope or is this just one of those things? What is the rationale? Long bed vs short bed maybe? Just wondering, thanks for any info.

-Josh

turtle1056 · Post by **turtle1056** » November 2, 2007, 2:50 pm

general rule of thumb for a truck is no shaft over five feet long to prevent whip or occilations, or bending, hence the midspan hanger bearing, and two piece shaft. It also allows for smaller tube sizes

is why u see multi piece shafts under larger five ton n up straightframes

you will notice that the longer one piece shafts have a very much larger tube size to alleviate this problem

6166 Junkyard Dog · Post by **6166 Junkyard Dog** » November 2, 2007, 5:41 pm

my F-450 has 4 drivesahfts under her

blackagatha · Post by **blackagatha** » November 3, 2007, 12:12 am

6166 Junkyard Dog wrote:my F-450 has 4 drivesahfts under her

WOW!!! that sounds like a bloody pain to determine which one is the bad Ujoint... haha

I read somewhere that on a 1 piece driveshaft, there is actually some sort of "surging" that takes place

Supposedly, as it turns, it spins a bit quicker right when the Ujoints flip over. But if there was 2 ujoints in a cluster, it would relieve this issue. I don't "fully" understand it, but I got a decent grasp of it anyway.

banjopicker66 · Post by **banjopicker66** » November 3, 2007, 6:32 am

I hope I am not overstating the obvious, but the need for a two piece driveshaft in the pickups often depends on the transmission used in the truck, more than the length - although that is a factor in larger trucks.

The driveline requires an inline slipjoint allow for the change in angle declension between the fixed transmission and the floating axle. When the truck is loaded, the angle is smaller, and the driveshaft needs to be shorter; when the truck is empty, the angle is greater, and needs to be longer.

Most automatic transmissions have a slip joint for the output shaft. Most manual transmissions, and some older automatics like the COM have a fixed output shaft. The driveline must incorporate a slip joint elsewhere, hence the two piece driveshaft.

Even larger trucks will have this feature in place.
Perhaps I have misread your question?

Post by **Greg D** » November 3, 2007, 5:00 pm

When I get the 5 speed for my Uni I will pull the driveshaft too so I have one to get shortened. I now have a carrier bearing under the truck, this will eliminate that.

ezernut9mm · Post by **ezernut9mm** » November 3, 2007, 6:00 pm

i have a one piece out of a 66 f100 long bed, but i can't remember if it was an auto or manual truck.

Combat_Medic · Post by **Combat_Medic** » November 3, 2007, 10:34 pm

Wow, learn something everyday. Thank you guys for the information - Banjo and Turtle especially. Once again, free exchange of knowledge for the win.