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Found some 3/4 ton axles. How hard is this swap into a K5 and are these what I need?

Polymath

Polymath

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I found these axles nearby for a good price. Might blow my budget for a few months but i'm building a 489 on the side for a later swap and want to make sure I don't snap the stock axles. They are Dana44 and 14bff with 4.10 gears. Came out of a '77 chevy 2500 pickup which I confirmed was not a dually.

Are these pretty much a direct fit swap into an '85 K5? Or are there modifications that have to be made? Maybe my searching was not thorough enough but I couldn't find any detailed writeups about which axles from what years are an easy swap.

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direct swap. since the rear is from a 3/4 ton you will not have to move spring perches and such. of course you will need a different ujoint at the diff end.
 
Might need to either rotate perches, or shim rear to get the correct pinion angle. Since you are shorter wheel base. Get a master cylinder for the 77 3/4 ton.
 
By correcting the axle yoke, are you referring to changing the driveline angle? I was planning to account for that when/if I did a lift anyway. I assume someone makes angled shims but if not I can mill some out.
Or are you saying I should buy a different yoke to match the ujoints on the driveshaft so I'm not limited to special orders?
 
I would run the adapter u-joint until you do the lift. Then when you get the driveshaft lengthened you can go to 1350 on the driveshaft. It's also possible that without the lift your driveshaft will be too long.
 
Polymath said:
By correcting the axle yoke, are you referring to changing the driveline angle? I was planning to account for that when/if I did a lift anyway. I assume someone makes angled shims but if not I can mill some out.
Or are you saying I should buy a different yoke to match the ujoints on the driveshaft so I'm not limited to special orders?
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So yes, to different conversations going on here. On the axle/pinion angle there’s a specific way you want to set that up based on how the driveline is built so if you have a two joint or three joint shaft. The easiest way to understand that is to go to Tom Woods Drive shaft Website and look at the information they have. It explains the angles that you want those set up I typically point opinion down 1 to 2° so that way when it’s moving and under torque it brings the angle back up to alignment.

The second parts about do you joint on the rear axle. Conversion joints are OK if you’re not going to push anything very hard using a big engine like you have I would be tempted to run a 1350 or 1410 U joint series in the drive shaft is a whole, which is likely the U joint that is already set up for on the axle
 
Understood. If I do lift it, I was considering an SYE anyway so adjusting driveline angles has been thought of, if maybe not needed. I may just tuck some 35's in there and be happy with it for a while. I'm trying not to get stuck in a "while-i'm-in-there" loop.
 
Polymath said:
Understood. If I do lift it, I was considering an SYE anyway so adjusting driveline angles has been thought of, if maybe not needed. I may just tuck some 35's in there and be happy with it for a while. I'm trying not to get stuck in a "while-i'm-in-there" loop.
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Yeah that way of thinking can eat a lot of time and or money
I try not to have anything apart for very long. The longer it sits in one spot, the higher the specific gravity becomes, the less likely is to move later.
 
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I did a cut down 3/4 ton rear driveshaft for mine when I swapped axles. Both 1/2 and 3/4 ton trucks had NP208 transfer cases but the 3/4 ton driveshaft will have bigger u-joints and be a direct bolt up to that bigger rear diff without changing yokes.
 
The 14b will be an increase in strength the d44 will not increase your axle strength over the 10b you have now. But the the fact it’s 8lug and the ratio matches the rear is the bonus. That saves a lot of bs swapping the 8 lug parts from the knuckles out. If you intend to wheel the K5 with that big block an investment in chrome-moly front axle shafts would be smart. Though if you keep the front diff open the stock shafts may survive for a little while.

The size of the 14b being larger in every direction will effect your driveshaft length. If you compare the distance from the axle centerline to the pinion yoke to your 10 bolt and the 14b you’ll find the 14b yoke is further forward. That will reduce your driveshaft length. Factor in a 208 tcase with a slip yoke output and you may find the stock shaft has the slip bottomed out in the tcase or really close. Adding a lift might extend the length slightly but the angles will be way off.

So while the 3/4 ton 14b is a bolt in affair you may have to make some adjustments to deal with these other issues.

In my case with a ‘91 k5, 14b 4” lift with a shackle flip out back I had to make many adjustments. First the pinion angle with the shackle flip was garbage. Chucked the rear u-joint within the first 20 miles having it together. After a ton of research I chose to go to a cv (double carden) rear shaft. I kept the slip yoke in the 241 and the custom shaft I had built with a bolt on slip shaft to mimic the stock shaft and avoid having to move to a sye. The cv shaft required a major pinion angle change. I had to move it 8 degrees up so the shaft and pinion angle matched (per multiple guides online like Tom Woods).

As many changes spur further changes that increased pinion angle rotated the drive mr side shock mount down so much I couldn’t bolt in a standard shock because the can hit the housing before you could get the bolt in for the shock on the mount.

I ended up getting new lower shock mounts from ruff stuff, cutting the old off and welding the new on for a better angle.

Using the pinion angle shim works but isn’t ideal. Hindsight being what it is, I should have just got new spring mounts and burned them it at the right angle. Again, either way works but not having the shims to possibly wiggle out is a little more secure.
 
Good to know. I hadn't thought of the shock mounts rotating too far down. I won't be doing any crazy rock crawling. This is a camping/hunting truck with daily driver potential.

A secondary reason for this swap is the 4.10 gears. I've got 3.08's with open diffs now. So i'd be looking at swapping both gear sets some day anyway, and that isn't cheap or easy either. Just seems to make sense doing the 3/4 swap with the correct gears already in the axles.
 
Precision #447 conversion u-joint.

Very simple swap. Slap it together, and then see what you need. Generally nothing.

Martin
 
Polymath said:
Understood. If I do lift it, I was considering an SYE anyway so adjusting driveline angles has been thought of, if maybe not needed. I may just tuck some 35's in there and be happy with it for a while. I'm trying not to get stuck in a "while-i'm-in-there" loop.
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that is good thinking. I don't know anything of your situation but a lot of times people will start to do a simple mod and it snowballs and soon they have a project that is sitting for 5 years because it snowballed and life happened.
 
Well, I now have two axles clogging up part of my garage. Poor old motorcycles got relegated to the back yard with a tarp. These allegedly have new bearings everywhere and some manner of limited slip in the rear too, so that's a nice bonus.
 
Polymath said:
Well, I now have two axles clogging up part of my garage. Poor old motorcycles got relegated to the back yard with a tarp. These allegedly have new bearings everywhere and some manner of limited slip in the rear too, so that's a nice bonus.
Click to expand...
:sign6:
 
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