Why did some SWB trucks have a two-piece drive shaft and others not?

[406 Q-ship]

It is not a "Heavy Half" thing to have 2 piece driveshaft.  My 74 C10 350 Th350 12 bolt 2wd SWB with 56" 8 leaf rear springs has a one piece driveshaft.  I would bet it has something to do with the manual transmission.

[78 Chevyrado]

maybe they just switched it up randomly so the assembly line workers didn't get bored...

[2502]

my 79 was the olds diesel originally, it has a 2 piece driveshaft, it's a shortbed. the 80 i bought has a one piece, and when i swapped the chevy 350 over, of course the two piece didn't mate up, so the one piece outta the 80 had to come with it. or HAS to come with it, cuz i still didn't get that far.

[VileZambonie]

http://www.rodandcustommagazine.com/techarticles/0608rc_driveshaft_tech/index.html

[Captkaos]

I didn't say ALL of them..

....HD package called Heavy Half in the early years and they generally had 2 piece driveshafts and 56" leafs.

Does the TH350 in question on the HD truck have a long tailshaft?  Most trucks didn't get the long tails, they got medium tails.  this will reduce the length of the driveshaft allowing a 1 piece to work.  Not to mention we are talking about truck over 30 years old, how many are still in the same setup they were that long ago..

[406 Q-ship]

I didn't say ALL of them..

....HD package called Heavy Half in the early years and they generally had 2 piece driveshafts and 56" leafs.

Does the TH350 in question on the HD truck have a long tailshaft?  Most trucks didn't get the long tails, they got medium tails.  this will reduce the length of the driveshaft allowing a 1 piece to work.  Not to mention we are talking about truck over 30 years old, how many are still in the same setup they were that long ago..

I did not say that all of anything got or did not get a certain driveshaft, I was stating that my truck is a "Heavy Half" (it is on the RPO sheet) and does not have a 2 pieces driveshaft.  It has no provisions for the crossmember for a carrier bearing and it was the original transmission to the truck.  So in my opinion the 2 piece driveshaft is not necessarily part of the Big 10 or the Heavy Half package.  I believe that to get the 2 pieces driveshaft it would take a HD 4 speed manual transmission.  Your correct about the medium length TH350, I miss typed there.

maybe they just switched it up randomly so the assembly line workers didn't get bored...

Naw cause then they would be Ford........

[VileZambonie]

It's not a manual transmission thing. They all have provisions for the crossmember. Most short tailshaft applications came with the two piece driveshaft. My 1974 C15 came stock with a 454, TH400 short shaft and two piece driveshaft with 3.73:1

[406 Q-ship]

It's not a manual transmission thing. They all have provisions for the crossmember. Most short tailshaft applications came with the two piece driveshaft. My 1974 C15 came stock with a 454, TH400 short shaft and two piece driveshaft with 3.73:1

See that is strange because the short tailshaft TH400 is not much different in length than a medium tailshaft TH350 (or a 700r4).  So  it is not a transmission length issue, it must just be the vehicles have to be equiped in a certain manor......hmmm.

[VileZambonie]

Different model, wheelbase and driveline configuration dictated which truck came with a two piece. Most two piece have the slip yoke integrated while many one piece had no integral slip yoke.

 It'd be nice if everyone could chime in with their specifications as long as it's the original driveline set up and maybe we can help identify which options were more poularly fitted with 2 piece shafts.

[frogman68]

Different model, wheelbase and driveline configuration dictated which truck came with a two piece. Most two piece have the slip yoke integrated while many one piece had no integral slip yoke.

 It'd be nice if everyone could chime in with their specifications as long as it's the original driveline set up and maybe we can help identify which options were more poularly fitted with 2 piece shafts.

76 GMC C3500 350 SM465 has the two piece 

[KoolerSL2]

1985 C10 LWB originally 4.3 v6 TH400 10 bolt with 2 piece Drive shaft.
only 3 leaf rear with overload so i believe its a LD setup.

[123 pugsy]

79 GMC stepside / shortbox. 350/400 2 piece.

[VileZambonie]

It seems like every factory TH400 set up I've seen or had came with a 2 piece. My 1980 had a one piece with a TH400 but I'm not too convinced it came that way since it was an original 5.7 Diesel truck.