Why a 2 piece driveshaft?

[LennyGB53]

Does anyone know why the 1967 - 1972 Chevrolet C10 had a 2 piece drive shaft? I am replacing mine with mixed results. Advanced Auto Parts shows one picture and has a different part in the box. Auto Zone doesn't have it and NAPA was more expensive. I'm waiting to see what O'Reilly has for me now. That made me wonder why it's 2 pieces. I've had other cars and trucks that had drive shafts that long and there was no center support bearing.

[Jacfourteen]

It's a general rule that if the driveshaft is more that 72" then it needs to be two piece or it won't balance right.

[fixit-p]

As a drive line gets longer the critical speed goes down you can increase the critical speed by using a larger, thicker tube or both. Critical speed is the point where the drive-shafts rpm's match the frequency of the material and begins to bend off its centerline.

Good reading here>>> http://www2.dana.com/pdf/J3311-1-DSSP.pdf

Ujoint listings here w/dimensions>>>http://www2.dana.com/pdf/K350-1-DSSP.pdf

[JCD]

So there..

J.

[truckdude239]

if u need a new drive shaft find a reptual shop and have it built

[ChevLoRay]

Could it be that the leaf-spring chassis had a one-piece and the coil-spring chassis had a two-piece? I'm just asking and have no clue. My '96 GMC has leafs and a one-piece. My '69 has coils and a 2-piece. As long as the u-joints are good and properly installed and the center bearing is also good and the rubber in it is good, what is the problem?

[70BLAZERX2]

short or longbed 2-piece..they had those too..

If you need a shortbed driveshaft one piece to replace the 2 piece, you simply get a driveshaft out of a mid 80's 4door caprece...Its a bolt in..and easy to find..

[Jacfourteen]

Originally Posted by ChevLoRay

Could it be that the leaf-spring chassis had a one-piece and the coil-spring chassis had a two-piece?

My 68 GMC is leaf and it has a 2 pc shaft.

[mr.chevy]

Originally Posted by 70BLAZERX2

short or longbed 2-piece..they had those too..

If you need a shortbed driveshaft one piece to replace the 2 piece, you simply get a driveshaft out of a mid 80's 4door caprece...Its a bolt in..and easy to find..

Are you serious? I am turning mine into a short bed and I need a drive shaft. Does that mean it will bolt on for an automatic or manual transmission?
And what is the length of it? do you know it off hand?

[Sport/Truck]

Originally Posted by ChevLoRay

Could it be that the leaf-spring chassis had a one-piece and the coil-spring chassis had a two-piece? I'm just asking and have no clue. My '96 GMC has leafs and a one-piece. My '69 has coils and a 2-piece. As long as the u-joints are good and properly installed and the center bearing is also good and the rubber in it is good, what is the problem?

I'm thinking it's the transmission.... My neighbor has an original 72 stepside w/coil springs and it has a one piece.

[Sport/Truck]

Originally Posted by 70BLAZERX2

short or longbed 2-piece..they had those too..

If you need a shortbed driveshaft one piece to replace the 2 piece, you simply get a driveshaft out of a mid 80's 4door caprece...Its a bolt in..and easy to find..

That sounds real promising. You have any pictures or other info?
s/t

[ChevLoRay]

When I made my comment, I meant for it to say that I didn't know and was just making a comment. I have no proof. My SWB has a small block and a TH400, as well as a 2-piece driveshaft.

I can see why longer wheelbase vehicles have multiple section driveshafts, so the mystery has been the subject of this post.

[Sport/Truck]

Originally Posted by ChevLoRay

When I made my comment, I meant for it to say that I didn't know and was just making a comment. I have no proof. My SWB has a small block and a TH400, as well as a 2-piece driveshaft.

I can see why longer wheelbase vehicles have multiple section driveshafts, so the mystery has been the subject of this post.

I don't know either, and I'm just adding what I know to help narrow it down.
Both my neighbor and I have short beds. Mine is 350 auto with coils = 2 piece.
The short step manual trans w/ 1 piece.

[Jacfourteen]

Originally Posted by ChevLoRay

When I made my comment, I meant for it to say that I didn't know and was just making a comment. I have no proof. My SWB has a small block and a TH400, as well as a 2-piece driveshaft.

I can see why longer wheelbase vehicles have multiple section driveshafts, so the mystery has been the subject of this post.

I'm not sure what the logic is why some have 1 pc and some have 2 pc, I was just saying what I have. I knew you were just throwing ideas out there, I wasn't bagging on you or anything.

[70BLAZERX2]

Originally Posted by mr.chevy

Are you serious? I am turning mine into a short bed and I need a drive shaft. Does that mean it will bolt on for an automatic or manual transmission?
And what is the length of it? do you know it off hand?

It will fit the auto ,Yes right length for v8 auto.. some are 54 inches weld to weld,depending on what trans they has..200R4 or 700r4..

the later 86-up are 55 inches weld to weld When you get your truck back together,take your old one,slide it in the trans where the yoke normally rides,then just measure it..and go to the yard and pick one out.

That way you know..I worked at a big yard years ago..and you found what worked..

[LennyGB53]

Mine is a short bed flare side with a 2 piece shaft. I had a 1976 Ford with a 8 foot bed and it had a one piece shaft. The length thing makes no sense. All of the older cars that were huge had one piece shafts with or without coil springs. Think of the old Buicks, Olds and Packards. My shaft is fine. I'm changed transmissions and now I'm replacing the u joints and center bearing. My last truck was a '68 long bed and sent from a 3 speed manual to a TH350 and we kept the same driveshaft.

[dan42]

They all came from the factory with a two piece driveshaft, long bed or short bed. If they have a one piece driveshaft, it's been converted.

[LEEVON]

to answer your question, I like my 2-piece because it doesn't have the same vibrations that every single 1-piece in my lowered trucks has.

[Keith Seymore]

The "critical speed" post is correct.

What you guys might be missing is that propshaft critical speed not just based on wheelbase but is also based on trans type (length), rear axle ratio, tire size, and engine type (larger engines allowing a higher top speed).

So - a long wheelbase truck with a low (numerical) rear axle ratio spins the shaft slower and might get a one piece, but an otherwise comparable truck with a high rear axle ratio might get a two piece.

One other comment - critical speed is not directly related to balance, but rigidity. When the shaft exceeds it's critical speed it begins to bow in the middle and swing like a jump rope. Hence the disturbance and durability concerns.

K

[LennyGB53]

I guess I'll accept that. It just seems odd that some longer vehicles have one piece and a shorter C10 has a two piece. Perhaps it's due to the diameter of the drive shaft itself.

[ls1nova71]

Originally Posted by dan42

They all came from the factory with a two piece driveshaft, long bed or short bed. If they have a one piece driveshaft, it's been converted.

I've had two shortbeds, one 1972 250 6 cylinder with a turbo 350 all original, and a 1971 250 6 cylinder with a 3 speed manual, and both have had one piece driveshafts. There is not even anyplace for a carrier bearing to mount to on either one. There are holes in the crossmember that the trailing arms bolt to, but it doesn't look like there has ever been anything bolted or rivited to it.

[grs]

Have a drive shaft shop make a one piece. They will tell you how to measure it. Take the bracket that the carrier bearing bolts out of the truck.

[Keith Seymore]

Originally Posted by LennyGB53

I guess I'll accept that. It just seems odd that some longer vehicles have one piece and a shorter C10 has a two piece. Perhaps it's due to the diameter of the drive shaft itself.

Yep - the '73/'74 SWB 454 trucks had a two piece shaft. There's so many more variables than just wheelbase.

In the GMT400 and GMT800 versions we started using "exotic" materials like aluminum and carbon fibre wraps in larger diameter shafts - all with the motivation of taking some of those two piece applications and turning them into one piece (saving the additional center bearing hardware and complexity).

Believe me, the engineers wanted one piece shafts wherever they could get away with it, too.

K

[stich626]

Originally Posted by LennyGB53

Mine is a short bed flare side with a 2 piece shaft. I had a 1976 Ford with a 8 foot bed and it had a one piece shaft. The length thing makes no sense. All of the older cars that were huge had one piece shafts with or without coil springs. Think of the old Buicks, Olds and Packards. My shaft is fine. I'm changed transmissions and now I'm replacing the u joints and center bearing. My last truck was a '68 long bed and sent from a 3 speed manual to a TH350 and we kept the same driveshaft.

cars didn't tow or get loaded down with 1000lb or more..

[raycow]

Actually, quite a few GM cars began using 2 piece shafts as far back as the late 50s. This wasn't done because of shaft length or loading, but rather to allow a lower floor hump or accommodate an X-frame. Other makes may have done this too, but I happen to be personally more familiar with GM.

Ray