Help with Proper Driveshaft?

[72longbed]

Can somebody help me to determine what rear driveshaft is correct for a 71/72 4x4 K20 longbed with a Turbo 350? Was the factory unit a one piece or two piece? Did it have a 'slipjoint' in it from the factory? I'll be looking to buy a factory 'stock' setup for the K20 longbed.

Thanks,
72longbed

[krue]

2wd's came stock with 2piece drive shafts on the auto trucks. I'm not sure about the 4wd's.

[BowTieMan]

EDIT: Didn't think about the transfer case making the shaft shorter. Let me put my foot in my mouth. lol


I would think 4x4's would come with a 2 piece. I worked at a drive shaft shop and we wouldn't make any shaft over 61 in. long because it would never balance right.

[mrein3]

The 4x4s rear shafts are one piece.
And if you got a NP205, all 67-72s that came with a NP205 have the same length front and rear drive shafts. Any drive length differences were made up in the adapter between the tranny and transfer case.

If you find a 71 or 72 4x4 in a yard (I believe they were all NP205s), and it still has the rear drive shaft, you found the correct piece.

[Americanrider]

I have a 72 K20 drive shaft I was going to sell, I took these photos but the sale fell through and I decided to keep it. (along with the 350 trans & 205 transfer) There is a slip yoke from the rear of the 205 to the splines on the driveshaft. You can only see part of the slip setup on the tail of the transfer case. Here are all the pics I saved. If you need other measurements drop me a PM, I'll be glad to help.

[4x4Poet]

My two K20s came with one piece, slip-yoked, rear driveshafts with 1350 yokes. They were also made with 4 inch tubes that my driveshaft shop says are hard on u-joints because the tubing, being so far out from the centerline, measured lengthwise, puts somewhat excessive centrifugal force on the u-joint pins & caps. Somewhat excessive because it does take 100k miles or so to wear out the u-joints, depending on how religiously they were kept well greased. All those PO years with 4.11 gears on short, skinny tires @75-plus mph couldn't have helped.

For the K20 I drive, rather than install almost $50 worth of u-joints in an inferior design driveshaft with questionable slip yoke life remaining, I had them build a standard, better designed, shaft with thicker wall, 3" (or is it 3.5"? I forget) tubing and 1350 yokes to match.

[72longbed]

A big 'Thank You!' to all that have responded so far, this info is valuable. To Americanrider: can you please put the rear axle together with the yoke at the transfer case and give me an overall measurement of the driveshaft from U-joint center to center? I don't have a driveshaft to compare to and need to verify that the complete unit will fit under my truck. I understand that the slipjoint can give some for suspension differences, so maybe with the slipjoint in the mid-way position.

Thanks for the help everybody,
72longbed

[72longbed]

I took a measurement today from the transfer case yoke to the rear yoke at the deepest point of the U-joint cups: 62"

The NP205 transfer case is bolted into the frame at the factory location with NO tranny, no cab, no front clip yet. Only the weight of the engine and the bed is on the frame.

Does this length sound like its close to being able to use a stock 4x4 longbed driveshaft??

Thanks,
72longbed

[Rod]

Some of the rockwell case 4x4 had 2 piece rear shafts in the earlier years..

[Americanrider]

With the front yoke fully collapsed into the shaft it's 59 inches [center of U-joint to center of u-joint]. Normally it would be a little extended (with no load on truck and stock springs/tires) I would say about 60-62 is on the money.

[72longbed]

Here's the latest on this build-up. I tried to use the stock location for the transfer case in the frame and found that caused the engine to be so far forward that the Headers would not fit between the frame rails when bolted to the engine. The 700R4 in the 4x4 version adds about 1 7/8" to the overall length of the engine/trans/transfer case combo. So I went back to the factory engine cradle location and drilled 12 (friggin' twelve! ) new frame holes for the transfer case crossmember and side mount. That was a good bit of work, the steel in these frames is HARD.

So now I need to know if the factory type driveshafts will extend/collapse to fit the following measurements: Front shaft overall from deepest part of U-joint cup of DANA 44 yoke to U-joint cup of transfer case yoke is 31 3/4". (These measurements are made with a steel tape measure in a straight line, in place of where the driveshaft would go.) Rear shaft now needs to be 60" overall.

I was talking with another local Member of the Board and he has some stock 4x4 driveshafts that would not either extend far enough or collapse far enough to fit these areas?? Supposed to be for this era truck too?? Am I looking at custom driveshafts or can someone verify that stock 4x4 shafts will still work on this truck?? Maybe somebody out there has a driveshaft (either front or rear) thats not currently installed and can measure it to see if it will extend/collapse SAFELY to fit these areas please?

BTW, the truck has an HO72 rear axle, an NP205 transfer case and a Dana 44 8 lug front axle.

Thanks for any help on this,
72longbed

[Americanrider]

Here are the pics & measurements of the both 72 K20 drivelines from tip to tip.

[72longbed]

Thanks Boone,
Those are good Pics. Let me know if you want to sell either or both shafts.

72longbed