Why a 2 piece driveshaft?

[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

[mr.chevy]

Originally Posted by 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.

K

I may be understanding you wrong but,

That doesn't make any sense to me. If i have the same trans as you but i have 5.14's in the rear the drive shaft spins a lot faster than it would at as say a 2.73 ratio. I had a 3/4 ton 67 with 5.14 posi in rear and it had two pieces. It has to turn 5 times around before the tires turns around once. hence the high rpm at a low speed.

Larger engines don't have anything to do with top speed. unless you need tons of power to get to a ridiculous speed. your last gear in your trans is 1:1 unless its an overdrive. Gears in the differential more than anything allow for a higher top speed.

Also i was under the impression that it was the short beds that got the one piece. i could be wrong.

[fixit-p]

Originally Posted by mr.chevy

I may be understanding you wrong but,
That doesn't make any sense to me. If i have the same trans as you but i have 5.14's in the rear the drive shaft spins a lot faster than it would at as say a 2.73 ratio. I had a 3/4 ton 67 with 5.14 posi in rear and it had two pieces. It has to turn 5 times around before the tires turns around once. hence the high rpm at a low speed.

There you go right there, if an engineer were to do his critical speed calculations based on a vehicle speed of 60mph that 5.14 ratio may spin a 1 piece driveline at or near its critical speed, that same 1 piece driveline on the 2.73 ratio rear end @ 60 mph maybe well below its critical speed. Based on that logic the dive line on the 5.14 ratio rear end should be a 2 piece, larger diameter or different material.

Originally Posted by mr.chevy

Larger engines don't have anything to do with top speed. unless you need tons of power to get to a ridiculous speed. your last gear in your trans is 1:1 unless its an overdrive. Gears in the differential more than anything allow for a higher top speed.

.
Often times vehicles with smaller lower torque/hp engines were equip with lower gear ratios to compensate for the lack of power.

[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.

[Saloonwarrior]

Originally Posted by 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.

I was told by Sadler Powertrain to install yoke into transmission until it bottoms out, measure from center of yoke holes to center of rear housing yoke holes then subtract 1 1/4" for proper clearance.

[70STOVEBOLT]

Originally Posted by Saloonwarrior

I was told by Sadler Powertrain to install yoke into transmission until it bottoms out, measure from center of yoke holes to center of rear housing yoke holes then subtract 1 1/4" for proper clearance.

This IS the correct way to do it.

[68gmsee]

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.

They didn't all come with 2 piece shaft. I've got a 69 Chevy shortbed with coil and single piece. Never been converted. I also have a 68 GMC shortbed with springs single shaft. Also never been converted.

[Sport/Truck]

Originally Posted by 68gmsee

They didn't all come with 2 piece shaft. I've got a 69 Chevy shortbed with coil and single piece. Never been converted. I also have a 68 GMC shortbed with springs single shaft. Also never been converted.

Were they manual transmissions by chance?

[71meangreenc10]

Originally Posted by 68gmsee

They didn't all come with 2 piece shaft. I've got a 69 Chevy shortbed with coil and single piece. Never been converted. I also have a 68 GMC shortbed with springs single shaft. Also never been converted.

I have never ever, seen a stock 67-72 chevy truck with a factory one piece shaft...I have own many of these trucks, only two pieces.....

Maybe I am due, if they were available.....


Smitty

[Kidd-7]

I had my carrier bearing tear off the frame a few years ago; broke a u-joint & dropped the driveshaft. Had to have new "ears" welded on and a carrier bearing pressed on. Here is the shop that did it: http://www.samwinermotors.com/ excellent shop and very reasonable.

[LennyGB53]

That makes some sense finally raycow. Thanks...

[LennyGB53]

Stitch, many cars pulled camping trailers etc. that exceeded 1000 pounds. They put on Reese hitches and overload springs often to pull their camping trailers.

[stich626]

Originally Posted by LennyGB53

Stitch, many cars pulled camping trailers etc. that exceeded 1000 pounds. They put on Reese hitches and overload springs often to pull their camping trailers.

yes I know that, but the truck was engineered to do it..
at ride height or bumber drag'n.

tail drag'n a wagon and tow'n kills ujoints,, and gives a stock 1 piece tube a slight twist to it..
draw a line on a driveshaft in a wagon then tow 1500 miles and look at the line again.. unless you drove like a granma, it's got a slight twist to it..
even light power over wet r/r tracks will do it..
once it starts it only gets worse..

[Sport/Truck]

This thread has been long over due, and I appreciate such an excellent explanation to why some have different setups.

Sounds like the 2 piece is the better all around choice, as the 1 piece were used on trucks with lower gearing (Probably because it was cost effective).

2 piece was used for trucks that had higher gearing to keep critical mass down.

Do I have this correct?
s/t

[WIDESIDE72]

One piece ds' are always a larger diameter to compensate.

I have a 72 SWB step. I swapped in a 700r4. I slipped an old yoke I had into the trans, measured from where the middle of the front yoke would be to the where the middle of the rear yoke would be and got 55 1/2" at ride height. A few weeks back, I came across a Craigslist ad from someone selling a driveshaft out of an 85 Chevy SWB... It was 55 1/2" center to center as well.

[franks72]

I've allways wondered why people want to go with one peice shafts. I have had 5 of these trucks over the years and only had one carrier bearing go bad. There plenty strong .My truck now has the stock two-peice and I run this truck at the track. 4500lbs, 180 shot of nos and no problems. I just dont see the advantages of a one-peice. my .02 .

[WIDESIDE72]

Originally Posted by franks72

I've allways wondered why people want to go with one peice shafts. I have had 5 of these trucks over the years and only had one carrier bearing go bad. There plenty strong .My truck now has the stock two-peice and I run this truck at the track. 4500lbs, 180 shot of nos and no problems. I just dont see the advantages of a one-peice. my .02 .

Personally, I am only going to a one piece because of a trans swap and the one piece was $35

[franks72]

Originally Posted by WIDESIDE72

Personally, I am only going to a one piece because of a trans swap and the one piece was $35

Well I have to say I didn't think about cost on a swap, 35 bucks is hard to beat.

[raycow]

Originally Posted by franks72

I've allways wondered why people want to go with one peice shafts.

Two-piece is fine as long as the truck is COMPLETELY stock. Once you start with modifications it is difficult to set up all 3 U-joint angles so you don't get vibration. Modifications can include engine, transmission or rear end swap, raising or lowering. This problem is legendary on 58-64 Chev full-size passenger cars that have been modified. A few of those have been converted to one-piece for this reason, and it's not an easy conversion on this car.

With a one-piece it's easy - just set the rear end angle so the pinion shaft is parallel to the transmission output shaft and you are done.

Ray

[63chevyll]

i always throught it was due to the trailing arm as the pivot and the 2nd u joint being in the same area...

Well i was wrong, but havent had any issues with my 2 piece shafts and even when hard racing no issues

[67gmcstepside]

Not to highjack this thread but I just got my 2 piece back from Mr. Driveshaft (3/4 to 1/2 ton conversion) and it seems my second shaft might have been made to short. How much of the front drv shaft spline is showing in front to the rear drv shafts yoke. Mine is 1.25 inches. Seems too much???

[projectx]

I know this is an old thread but I'm thinking about installing a single shaft in my truck.

Has anyone had any issues installing a single driveshaft in their lowered truck?

Any suggestions on what shaft to use?

[gearys 5600]

I have a one piece shaft in my static dropped yellow 69, No problems, I had a local driveshaft shop build mine.

[pritch]

I thought about converting to a one-piece, but then I decided, why re-invent the wheel? It seems to me if I had to get a larger diameter, I would maybe run into clearance issues where it passes through the member that the trailing arms are connected to.

But I've always had one nagging question about two (or more) piece shafts. Does the carrier bearing(s) ever interfere with the movement of the yoke in the transmission? It looks to me like the carrier bearing is solid, I mean, not intended to have any give, so as the rear end travels up and down, forcing front and back movement onto the driveshaft, does it bind up at the carrier bearing?