Did the 1/2 ton short beds come with a two piece driveshaft?

[Gregski]

I am just wondering if the 1/2 ton C10s with short beds ever came with two piece driveshafts, or will I be looking for a Unicorn?

[mkmc69]

Yes. I had a 67 step side that had one and my 70 that I have now. So not quite a unicorn.

[67C10Step]

My 67 short bed is a two piece as well. My 70 model years ago was a one piece. If I ever swap to an automatic transmission I may go back with a one piece.

[71meangreenc10]

My 71 had a 2 piece. Original 250 6cyl with 3 OTT.

Smitty

[Smitty]

My '71 short Fleet side with the 307 and 3ott had a 2 piece. But when I went 350 with the 700 I went to the one piece.

[Gregski]

thank you all so much for your feedback I picked up a long bed two piece driveshaft today after learning that they all are the same length from the center bearing support to the rear axle, that will work for me as I am mating it with a Lexus GS450h transmission so I will need to have the front cut and a three bolt flange welded on anyway

got this from a super nice guy named Chris is Westley California for $150 (ish) bucks, the price went down the more things I put in my little to buy pile, ha ha

[Gregski]

I also learned how there are two types of drive shafts a skinny one (the size of your wrist) with a flimsly center support bracket and a heftier one with a stronger middle bracket like this one (I got this off of a 3/4 ton long bed) also from Chris in Westley California for $80 (ish) bucks (price adjusted the more suffs I bought) Chris is a great guy

[Gregski]

I don't mean to brag but I am a bit of a third degree rust belt Ninja with the wire wheel

[Gregski]

and 17 minutes later...

[Gregski]

let's not forget the doo dad, bird poop and all

[Gregski]

now it's ready for the media blasting cabinet and later DIY powder coating

[Accelo]

My 70 SHORT Box had a 2 piece. Original 250 6cyl with 3 on the tree.

[special-K]

Wore those bristles down a bit, did ya? Looks great.

I'd like to ask anyone giving 2pc SWB driveshaft info to include the engine and transmission the truck came with. I'm unclear on the rhyme and reason for 1pc vs 2pc driveshafts. It looks like 6cyl/3spd SWBs came with 2pc

[Gregski]

Originally Posted by special-K

Wore those bristles down a bit, did ya? Looks great.

I'd like to ask anyone giving 2pc SWB driveshaft info to include the engine and transmission the truck came with. I'm unclear on the rhyme and reason for 1pc vs 2pc driveshafts. It looks like 6cyl/3spd SWBs came with 2pc

I hear ya, here's an actual photo of the General's process for determining which truck gets which driveshaft:

hope this helps,

[Keith Seymore]

Originally Posted by Gregski

I hear ya, here's an actual photo of the General's process for determining which truck gets which driveshaft:

hope this helps,

I've been expecting this post.

My response:

It has to do with propshaft (aka "driveshaft") critical speed.

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) AND/OR any strange resonances in that particular combination (camping out on that resonance will break the trans/transfer case tailshaft housing).

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.

You can get around it by going to a larger diameter steel tube - or more expensive alternative materials like aluminum, carbon fiber, an aluminum/carbon wrap, or exotic materials like "metal matrix" (aluminum impregnated with other metals).

So - given two otherwise identical appearing trucks - there could be a tire difference that put it over the edge, or perhaps a different horsepower rating which would allow for a higher top speed, or some unseen bending resonance that shows itself during testing.

K

So - not only could we manipulate one pc vs two pc based on material selection, but the program team might even speed limit a vehicle (via pulling fuel or ignition) to limit top speed to allow a one piece configuration.

K

[Keith Seymore]

Originally Posted by special-K

Wore those bristles down a bit, did ya? Looks great.

I'd like to ask anyone giving 2pc SWB driveshaft info to include the engine and transmission the truck came with. I'm unclear on the rhyme and reason for 1pc vs 2pc driveshafts. It looks like 6cyl/3spd SWBs came with 2pc

Tim - if you EVER have any questions on any of this engineering stuff I am happy to answer them for you.

K

[Keith Seymore]

Originally Posted by Gregski

I don't mean to brag but I am a bit of a third degree rust belt Ninja with the wire wheel

Ha! I am an artiste with a die grinder.

We could make beautiful music together.

K

[mr.mud1]

Originally Posted by Keith Seymore

I've been expecting this post.

My response:



So - not only could we manipulate one pc vs two pc based on material selection, but the program team might even speed limit a vehicle (via pulling fuel or ignition) to limit top speed to allow a one piece configuration.

K

thank you sir,wonderful information that makes perfect sense once you explain it.

[Gregski]

Originally Posted by Keith Seymore

Tim - if you EVER have any questions on any of this engineering stuff I am happy to answer them for you.

K

Folks, Mr. Keith Seymore is a treasure trove of valuable information, he has helped me many a times with my '74 squarebody build, we must cherish him at all costs (and perhaps clone him) thank you sir!

[pjmoreland]

I owned a 67 shortbed that came from the factory with a one-piece driveshaft. It had a 250 engine, a 3OTT transmission and an overdrive unit. It also had 4.10 gears. The gears and overdrive were listed on the SPID. There was no center support bracket on the crossmember.

[fatbass]

My '71 K10 had a one piece even with a 4" lift and 33" tires, 3.73 gears and Limited Slip. I only replaced the U-joints once in 226,000 hard miles.

[Bob B.]

Originally Posted by Keith Seymore

I've been expecting this post.

My response:



So - not only could we manipulate one pc vs two pc based on material selection, but the program team might even speed limit a vehicle (via pulling fuel or ignition) to limit top speed to allow a one piece configuration.

K

As an example, my employer bought a large number of mid-2000's Silverado 4X2 2500HD's with 6.0L/4L80E powertrains. One year they all had fixed yoke transmissions with 2 piece steel driveshafts and a center support bearing. Next year they had slip-yoke transmission output shaft with a large diameter one piece aluminum driveshaft. I believe the trucks were spec'ed identically, in fact they may have been a continuation of the same order.

[palallin]

'67 Chevy C-10; 283/PG/12-bolt Rear: 2 pc w/ small carrier bearing.

[67swb72klb]

My 67 SWB 327 with a three speed 2 piece originally..

[va72longhorn]

I had a 72 SB GMC Sierra Grande with a 350/350 drivetrain. It had a two piece. The carrier bearing mount broke and I had it welded….. twice. After it broke the third time I replaced it with a single driveshaft out of a early 70’s chevelle, if I recall correctly. It was a exact fit. Never had another issue with it.