Why a 2 piece driveshaft?

[fixit-p]

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.

Here's a better explanation >>>> http://www.engineersedge.com/bearing...ing-bodies.htm

[Keith Seymore]

Originally Posted by fixit-p

Here's a better explanation >>>> http://www.engineersedge.com/bearing...ing-bodies.htm

That's what I said - "...it'll swing like a jump rope".



Makes me think of a joke: this engineer takes his tire into the Goodyear store to get it balanced. While he's watching the work get done (...because we always have to watch to make sure it's done right -lol) the young tire tech takes the weight displayed and splits it in two, putting half on the outboard face of the rim and the other half on the inboard face of the rim.

He asks the engineer: "do you know why I did that?"

The engineer clears his throat and says, "why, yes, in fact I do. If you were to put all the weight on one side, the offset of the wheel introduces a moment, the resulting force being proportional to the lateral distance of the offset and increasing with vehicle speed. The resulting magnitude can create a disturbance which can magnify, particularly at it's resonant frequency and be felt in the car at certain speeds, generating customer pleasability issues, erratic tire wear and/or durability concerns".

The kid looks blankly at the engineer and says "yeah. Cause if I don't it'll wobble".



K

[Dano69c10]

I had always thougth it was also a clearance issue. The 2-pc has the primary shaft level to the chassis and the secondary tilts downward to the rear axle. This set up would have more clearance than a 1-pc shaft that tilts downward from the tranny to the rear axle. If the wheelbase is small enough the difference in clearance is negligible, but as the wheel base increases it becomes a ground clearance issue with the driveshaft. Aside from what has been mentioned in previous posts. I could be wrong, it wouldn't be the first time.
Just my $0.02
Dano

[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.

[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.

[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.

[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.

[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

[Roman]

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 tranny?
And what is the length of it? do you know it off hand?

Mr. Chevy (or anyone), let me know what you find out. I'm in the same predicament. I just converted my long bed coild spring chasis C-10 to a short bed. I'm planing to keep everything else original 250 6 Cyl, 3 manual trans. But I need to resolve the driveshaft issue. My plan was to look in a bone yard for a one-piece driveshaft from a 67-72 6cyl, three on the tree tranny. Any suggestions? My other option was to have one custom built...suggestions?

[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.

[Kidd-7]

Originally Posted by Roman

Mr. Chevy (or anyone), let me know what you find out. I'm in the same predicament. I just converted my long bed coild spring chasis C-10 to a short bed. I'm planing to keep everything else original 250 6 Cyl, 3 manual trans. But I need to resolve the driveshaft issue. My plan was to look in a bone yard for a one-piece driveshaft from a 67-72 6cyl, three on the tree tranny. Any suggestions? My other option was to have one custom built...suggestions?

Sorry to high jack the thread here, but I'm curious; How did you convert from long bed to short? New frame or cut the old one? Also, do you know the length difference between the frames?

[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

[mr.chevy]

Originally Posted by Kidd-7

Sorry to high jack the thread here, but I'm curious; How did you convert from long bed to short? New frame or cut the old one? Also, do you know the length difference between the frames?

I had a c10 long bed frame that i cut down and welded back together and i am in the process of getting my bed off my truck to cut it down. I have a blog that has some pictures of what i have done so far. I should have a link at the bottom of this post. I can tell you specifics if you pm me and get my email.
Glad to help.

[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.

[Justin87]

My 95 V6 Camaro HAD a two piece drive shaft. Found out nobody but GM carried it and the price tag was $900 so I bought a one piece and have had no problems.

[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?

[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???

[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

[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?