Correct Driveshaft Length for 700-R4/NP208/14bolt FF

[scrap--metal]

the date code on the tires is 2016 LOL

That must've been one of the last sets made. I got my KO2's in 2017. I was thinking they changed earlier, but 5 year old tires are still babies in my book. That's why they still look good.

 

[scrap--metal]

have any pic side by sides or just the one on your truck? I just want to see and check something I also got lol

I do not have any side by side pics comparing the 52 3/4" driveshaft with the M1008 driveshaft. As soon as the 52 3/4" driveshaft came out, I slipped the M1008 driveshaft in to loose as little trans fluid as possible from the T-case.

What exactly are you trying to compare? You may be able to talk me into getting a side by side pic... It's just a lot of dicking around for a picture. Circumference measurements would be a lot easier.

 

[scrap--metal]

We still talking about driveshaft size?

Now that you mention it, there's getting to be more and more innuendos in this thread...

 

[AuroraGirl]

That must've been one of the last sets made. I got my KO2's in 2017. I was thinking they changed earlier, but 5 year old tires are still babies in my book. That's why they still look good.

the weather checking is definitely more pronounced this last year than when I put them on. If they werent sitting in a small tripod pile in my moms yard since they were replaced by my step dad on his old 2005 chevy truck a few years back, directly in the sun and weather, face up, fileld with water etc etc, Im sure they wouldnt be as bad. But considering they sat in the sun and froze a few times, etc, I commend them for still holding it together and thats after my winter using the plow and the truck definitely putting the weight on those front ones while the rear ones just did their normal duty. 2k on the rear + the trucks normal weight, with the nose of the truck favoring the front ones probably isnt that hard on a 10 ply tire pair on the rear lol. at low speed.

on the driveshaft thing, diameter, circumference, those both would work. Im just wanting to know the "large" ness of the driveshafts compared to mine. I can measure mine. If you have the diameter you can find the circumference with a simple equation and if you have the circumference.. well frankly you only really need one or the other. if you do that for at least the one you put on your truck(from CUCV) that would be appreciated. But if you also do your one you removed, I would appreciate that too.

I just dont know what mine came off of technically, and the shear amount of trucks that were snipped up and parted and came through etc I dont know what it would be. I learned the np208 and cross member I have were probably, but this probably was not certain, out of two different vehicles, because my uncle says he was pretty sure the truck the np208 and sm465 came out of wasnt the same wheel base but he could remember if it was a short bed truck, possibly out of a GMC jimmy(which they had for a few years apparently) or if it all came in like a trade.. basically I could have a driveshaft that was *close enough* and if that is the case, I may just seek a CUCV one like you

 

[AuroraGirl]

We still talking about driveshaft size?

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[scrap--metal]

So I climbed up in the attic and under Frank tonight. I wrapped some decoy cord around each driveshaft and cut it while wrapped as tightly as possible to get circumference measurements (my calipers don't have deep enough jaws to measure the diameter and the u joints get in the way on the ends). Here's what I came up with:

M1008 driveshaft is about 12.75" in circumference or 4" in diameter.

The shorter k20 driveshaft is about 11.375" in circumference or 3.5" - 3.625" in diameter.

I hope those approximate measurements are enough to help you figure out what you have.

 

[AuroraGirl]

thank you good sir. im supposed to stay off my feet but they also gave me a loophole saying if i am up on my foot i can wrap it and they failed to set unecessarily specific boundaries to define how much time/stuff I would exactly want to limit myself on or to so if anything its the doctors fault for not elaborating since he didnt forsee me semantically following his orders. So there may be some trips to see how large my OE driveshaft was, the one on the 77, and the one on the truck. maybe even the large 2 piece out back the shed. be interesting to see if my current one matches your removed k20 one.

 

[scrap--metal]

be interesting to see if my current one matches your removed k20 one.

Any luck figuring out what's in your truck for a driveshaft?

 

[AuroraGirl]

Any luck figuring out what's in your truck for a driveshaft?

ill find out today since I have to move it

 

[ak4life]

What's the correct length driveshaft between a 700-R4/NP208 and a 14 bolt FF with an 8' bed? Is anybody running this combo and willing to measure u-joint to u-joint for me?

"Frank", my '81 K20, was Frankensteined by the previous owner. As a result, many things aren't quite right. Now I'm trying to figure out the driveshaft.

I had a highway speed vibration and found the rear U-joint needed replacing. I fixed that and my vibration changed, but it's still there. Then, I noticed that there's some slop where the slip yoke slides into the T-case.

I'm pretty sure that my 52.75" driveshaft is too short and it's not engaging the tailshaft bushing like it should. There's about 4 and 1/2" of machined yoke exposed outside of the T-case. All my other GM's have 1" to 2" exposed. If I slide the yoke all the way into the T-case, the driveshaft feels nice and tight.

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55 inches i just had one made for exact components....81 longbed 700r4 np208 except mine has 12 in lift....but even without the lift the driveline was only one inch shorter at 54"

 

[ak4life]

That's a lag screw holding the x member??
FWIW, the xfer case can not be "too far forward" Unless there's some wizardry there I don't understand...
Motor mounts set the position of the drivetrain first (or most forward) and the connections between the engine trans and xfer case are non adjustable. You cant "move" the transfer case fore and aft. And I totally don't understand the "upside down" comment on the xfer case x member. But based on the many previous discussions you've had about your drivetrain, if the truck goes forward and backwards at 10mph without parts falling out, I'd call it a win for a plow truck that doesn't hit the road.

Uhhhh yes you can and obviously it has been done..... you ever see how a hotrod is built from scratch ?

 

[ak4life]

FWIW, I'm still looking for a driveshaft measurement from anyone running a 700-R4/NP208/14bFF in a K20 with an 8' bed.

I have two more potential leads as of this week, one in New York and one in southern MN. If those fall through, I'll likely be having a new driveshaft made.

Its 54" inches without a lift and 55"with a 12 inch all suspension lift no blocks...
Mine is a 81 single cab longbed, 700r4, 208 tcase, 14 ff rearend , i just has my driveline built, havent gotten a chance to drive it yet (no brake lines) but it seems itll work perfectly....it sits about 2 inches out of the tcase for movement

 

[ak4life]

I do believe the rear springs to be good. I know there are no broken leafs (or leaves, lol), and the truck sits level from side to side. The leaf springs have a similar amount of rust as the frame rails, so I would assume that they've never been off the truck but that could be incorrect.

The wheels look like they sit where they should in the wheel wells, but could it be possible that the springs or axle are put together wrong? That's something I have not spent as much time investigating.

Pinion angle can definitely affect driveline vibrations, 2nd gen Camaros are notorious for that issue, but the slop where my slip yoke enters the NP208 is more than an improper pinion angle could cause. I have no idea on what kind of Chevy truck each component was sourced from.

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[ak4life]

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[ak4life]

I do believe the rear springs to be good. I know there are no broken leafs (or leaves, lol), and the truck sits level from side to side. The leaf springs have a similar amount of rust as the frame rails, so I would assume that they've never been off the truck but that could be incorrect.

The wheels look like they sit where they should in the wheel wells, but could it be possible that the springs or axle are put together wrong? That's something I have not spent as much time investigating.

Pinion angle can definitely affect driveline vibrations, 2nd gen Camaros are notorious for that issue, but the slop where my slip yoke enters the NP208 is more than an improper pinion angle could cause. I have no idea on what kind of Chevy truck each component was sourced from.