2-Piece Shaft swap into a K20 Longbed

[SquareRoot]

I'm about to swap my 208 tcase with slip yoke for a 205 with fixed yoke. The 205 setup is several inches shorter and therefore makes my driveline several inches short. The correct length shaft ends up being right on the edge of what's acceptable for a steel shaft. I suppose I could bite the bullet and get a custom hyper expensive 5 inch aluminum shaft but I think I'd rather just use the 2 piece setup I pulled from an 89 burb.

With that said, I'm having a hard time trying to visualize where I need to locate the carrier bearing. I doubt the underside of the burb is even close to the K series. Am I left with having to fab a crossmember to bolt the carrier bearing too?

Anybody with experience or knowledge (or PICS) of a long-bed with a 2 piece shaft?

 

[Bextreme04]

Its going to be a custom setup, so yes you would need to custom fab a crossmember. I'm having a hard time visualizing how you could possibly be that short in the drivetrain to need a two-piece driveshaft. I think mine with a TH400/205 is like 52"... maybe even shorter?

Since you have the fixed yoke output, your best bet would be to get a custom CV driveshaft from someone. Swapping my rear springs to GMT-400 61" springs basically pointed my yoke straight at the output on my 205, so if I ever find a SYE kit for mine that's my plan.

 

[SquareRoot]

I'm going to crawl under there tonight and get a rough measurement again. I swear last time I did this it was right at about 63 inches. I know losing that long snout on the 208 for the slip yoke was like an additional 8 inches going to a fixed yoke. The 14FF is also a inch shorter in the front than the 14SF that was in there. You really think I need a CV shaft? I know I need a slip shaft but what does the CV provide? If it's better, and I'm getting a custom shaft anyway I have no problem paying extra for it.

 

[Bextreme04]

I'm going to crawl under there tonight and get a rough measurement again. I swear last time I did this it was right at about 63 inches. I know losing that long snout on the 208 for the slip yoke was like an additional 8 inches going to a fixed yoke. The 14FF is also a inch shorter in the front than the 14SF that was in there. You really think I need a CV shaft? I know I need a slip shaft but what does the CV provide? If it's better, and I'm getting a custom shaft anyway I have no problem paying extra for it.

Mine is a 14FF also, but slip yoke on the 205. If you have any lift over about 4" you really need the CV to help with the angles. It keeps everything from binding up and lets it run much smoother. That's why you have the CV on the front.

Maybe mine is so short because I have the older Figure 8 adapter and the slip yoke?

 

[SquareRoot]

Mine is a 14FF also, but slip yoke on the 205. If you have any lift over about 4" you really need the CV to help with the angles. It keeps everything from binding up and lets it run much smoother. That's why you have the CV on the front.

Maybe mine is so short because I have the older Figure 8 adapter and the slip yoke?

2 inch lift but it may still be worth it. I'll look into it. My trans mounts directly to my 205. I have the rare 6 bolt round case. So yes, that's another two inches lost. Lol

 

[squaredeal91]

I've lowered the transfer case on these before. Helps with driveshaft angle.

 

[squaredeal91]

These are from my 91 yellow 3500. Was originally 2wd had to drop it down and move it over with that tubing. Also cut 14" out of it.

 

[squaredeal91]

From a 73 c10

 

[SquareRoot]

@squaredeal91

Thanks for the pix

 

[nvrenuf]

I could be wrong but I didn’t think GM used a 2 pc driveshaft on any 2 door pick ups (not C&C) which would mean you should be fine with a 1 pc. I’ve seen TONS of lwb sky high trucks with 1 pc shafts.

That said, if this is a dedicated wheeler I have seen one guy with a lwb truck and a 2 pc shaft but the purpose was to use a short, steep rear most shaft (w/ CV) for obstacle clearance.

 

[squaredeal91]

2 door long bed has 2 piece. My 73 c10 parts rig had a 2 piece and 85 too. The longest single driveshaft I've seen were on a chevy van

 

[nvrenuf]

Sorry, I should have specified 4wd.

 

[SquareRoot]

So, I took some actual measurements tonight. I knew my mind wasn't playing tricks on me in trying to recall the estimated length I came up with a while back. The big difference is between the Slip yoke 208 and the fixed yoke 205. Almost a foot difference! Starting out with a 52.5 inch shaft and adding 11 inches plus an inch to recenter the rear end results in a 64.5 inch shaft. Most shops won't go over 63 inches on a steel shaft. So I'm back to a 1 piece, lg. diameter aluminum shaft or a two piece. I see several advantages of the 2 piece over the one.

 

[Keith Seymore]

I see several advantages of the 2 piece over the one.

I never thought I would ever hear anyone say that.

One thing to consider is your anticipated vehicle top speed. The shaft critical RPM is a function of shaft material, diameter, wall thickness, vehicle speed, rear axle ratio, tire diameter, and maybe a few more variables.

The shaft was designed to handle some predetermined top speed, typically 106mph or 120mph. So one way to control the shaft rpm is to slow the F down.

You might ask yourself if you ever intend on going that fast in this thing, and if not, that might be a consideration that moves you back to a one piece if you are on the fence.

(I always do a one piece if I there is any way to get away with it).

K

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[nvrenuf]

When looking at measurements vs max tube length don't forget that with a fixed yoke tcase the slip yoke assembly is a part of the driveshaft (rather than the slip being on the tcase side of the u-joint), this will consume about a foot of that overall length.