78 axles in 72?

[72 k15]

Will a 14 bolt axle and dana 44 out of a 78 fit in a 72 gmc k15? Wanted to buy them for the 4.10 gearing they have and put em in as a upgrade. Looks like i saw the front will go right in but the rear perches will need to be moved?

[mongocanfly]

I think your correct..the fronts will bolt right in...rear spring perches will need moved....just pull a tape on the rear center2center on both and it'll let you know...

[72 k15]

Originally Posted by mongocanfly

I think your correct..the fronts will bolt right in...rear spring perches will need moved....just pull a tape on the rear center2center on both and it'll let you know...

I was wondering Beacuase the guy I am buying them from says they will just drop in.

[mongocanfly]

I know my 91 k20 14bolt and my 67 k20 eaton are different width spring pads....
The front swapped with no issue...had to move the rear spring pads...I'd just git him to measure it to compare it to yours...moving spring pads isn't a big deal...just cut the old ones off and weld on a new set..
And the wms 2 wms is different as well...

[Jeff's bowtie's]

The 3/4 ton14 bolt will require spring perch relocation and a 1 ton 14 bolt is a direct bolt in

[72 k15]

Originally Posted by mongocanfly

I know my 91 k20 14bolt and my 67 k20 eaton are different width spring pads....
The front swapped with no issue...had to move the rear spring pads...I'd just git him to measure it to compare it to yours...moving spring pads isn't a big deal...just cut the old ones off and weld on a new set..
And the wms 2 wms is different as well...

Forgive me but what does wms mean? And could I just weld the perches to the angle on the old axle or do I have to do some double knot ciphering to get it rihgt?

[sweetk30]

wms = wheel mount surface .
srw = single rear wheel .
drw = duel rear wheel .
c&c = cab & chassis . narrowest width rear of the 14ff .
14ff = 14 bolt full floater axle .

there is srw and drw then drw c&c for 14ff axles .

so if you can post up pics before you buy so we can help you get the correct stuff .

and if no lift kit or stuff like that then yes you can weld the perches to the same angle as the old axle .

there is super beefy aftermarket leaf spring perches out there that work better than old and are cheeper than new stock style wimpy ones . and no need to save the old when there so cheep .

barnes 4x4 has them . sells a lot on ebay .
ruff stuff specialtys has them .
diy4x.com has them .
offroad design has them .

some places have axle swap kits with perches / spring plates / u-bolts / shock mounts all in 1 package deal .

[Mike C]

I built a lightweight jig off my original perches to align the shock mounts then i just put the new perches on at the same pinion angle as the original setup at the original width.

No measurement origami.

[72 k15]

Originally Posted by sweetk30

wms = wheel mount surface .
srw = single rear wheel .
drw = duel rear wheel .
c&c = cab & chassis . narrowest width rear of the 14ff .
14ff = 14 bolt full floater axle .

there is srw and drw then drw c&c for 14ff axles .

so if you can post up pics before you buy so we can help you get the correct stuff .

and if no lift kit or stuff like that then yes you can weld the perches to the same angle as the old axle .

there is super beefy aftermarket leaf spring perches out there that work better than old and are cheeper than new stock style wimpy ones . and no need to save the old when there so cheep .

barnes 4x4 has them . sells a lot on ebay .
ruff stuff specialtys has them .
diy4x.com has them .
offroad design has them .

some places have axle swap kits with perches / spring plates / u-bolts / shock mounts all in 1 package deal .

Picture from the seller.

[mongocanfly]

14 bolt full floater...I also see some front axle parts laying in the floor along with rear axle parts..are you buying them in the torn apart state?....I would be Leary of something somebody tore apart and stuck back together....unless I really knew the axle owner...

[72 k15]

Originally Posted by mongocanfly

14 bolt full floater...I also see some front axle parts laying in the floor along with rear axle parts..are you buying them in the torn apart state?....I would be Leary of something somebody tore apart and stuck back together....unless I really knew the axle owner...

I am kinda Leary also he wants 350 for Dana 44 and 14 bolt only want them for the 4:10s would be cheaper than rebuilding mine. So I see I need to move the perches then?

[mongocanfly]

I'm gonna say yes..spring perch needs moved..and probably the shock mounts as well...only way to know for sure what needs done is pull a tape on it.....
Something else I wonder about is the driveshaft length.....
also the total axle width will be wider (I think) than your axles...if you've got a Eaton axle seems like I saw that gears aren't being made for the anymore....( again,I think)... ..
350 is cheap enough...but it would scare me that he tore them apart..and why...

[72 k15]

Originally Posted by mongocanfly

I'm gonna say yes..spring perch needs moved..and probably the shock mounts as well...only way to know for sure what needs done is pull a tape on it.....
Something else I wonder about is the driveshaft length.....
also the total axle width will be wider (I think) than your axles...if you've got a Eaton axle seems like I saw that gears aren't being made for the anymore....( again,I think)... ..
350 is cheap enough...but it would scare me that he tore them apart..and why...

I honestly don’t think all that would be worth it I might just put some 4:10s in my axles instead. Who makes some rebuild kits and gears that won’t take my wallet unlike Yukon, although if they make good stuff might buy from them.

[mongocanfly]

Do you know what axles you have...front and rear...?....Yukon makes great stuff
What gears do you have now?...also tire size and trans you have?

[72 k15]

Originally Posted by mongocanfly

Do you know what axles you have...front and rear...?....Yukon makes great stuff
What gears do you have now?...also tire size and trans you have?

Danna 44 and 12 bolt Orginal Posi gearing tag says 3.07. Going to be running 33s and nv4500.

[mongocanfly]

You'll have to change the rear diff/locker as well to go from 3.07 to 4.10s...12bolt series 3 to series 4..
Your close with your ratio choice...I'm running 33s with a nv but I went 4.56s
Youd be better off buying the axles already setup from another truck...

[kwmech]

Installing the 14 bolt, aside from moving the spring perches, you will also have to move the shock mounts and mess with the parking brakes cables. You will also have to freshen up the rear driveshaft and install either a conversion joint or just go 1350 series with the driveshaft mod.

[burnin oil]

I have to second the Barnes4x4 stuff also. I used there jeep kit to install a Ford 8.8 in a Jeep TJ. Kit was outstanding other than the directions for locating the brackets. They also sell on Amazon. That is where I bought the kit at since it was actually the cheapest there.

[72 k15]

Originally Posted by mongocanfly

You'll have to change the rear diff/locker as well to go from 3.07 to 4.10s...12bolt series 3 to series 4..
Your close with your ratio choice...I'm running 33s with a nv but I went 4.56s
Youd be better off buying the axles already setup from another truck...

You said I have to get different carriers I thought Yukon made 4.10s that fit the 3.73 and down carriers front and rear?

[mongocanfly]

not sure about Yukon but I think Richmond makes what they call a thick gear 4.10 for a series 3....

[Mike C]

Several manufacturers make the thick gears. But I would take advantage of the opportunity to upgrade to the 3/4 ton axles if it were mine. And I did with a set of 4.10 geared axles from an ‘86 3/4 ton Suburban. I used the semi-float rear though. After breaking 6 different 12 bolts one way or the other in my Jimmy this has been one of the better upgrades I have done. You may have to shorten the driveshaft if you aren’t running any lift in your truck, but I would recommend drilling a new locator hole in the spring perch and moving the rear axle back one inch. That better centers it in the wheelwell any how. You will be paying to have custom shafts made for both ends anyhow when you swap the NV4500 in.

[El Dorado Jim]

Originally Posted by 72 k15

I was wondering Beacuase the guy I am buying them from says they will just drop in.

Like someone else said, you will have to move the spring perches and the shock mounts are different also,and have to be moved, I did this in my 72, not that big of a deal, but the shock bolt holes are bigger on the 3/4 ton axle, I just welded a washer on each side of the shock mount that had a little smaller hole in it....

[scott123]

Originally Posted by El Dorado Jim

Like someone else said, you will have to move the spring perches and the shock mounts are different also,and have to be moved, I did this in my 72, not that big of a deal, but the shock bolt holes are bigger on the 3/4 ton axle, I just welded a washer on each side of the shock mount that had a little smaller hole in it....

The shock mount holes are often forgot on this swap.

I have both welded washers, cut hangers and replaced them as well as ordered them from a race car shop such as Stockcar products, etc..

Good call, the small details of the shock mount hole is often overlooked.

Scott

[ClassicJimmy]

I'm in the process of doing the same thing, mine is 75 K25 into a 71 K5, & I'm wondering if there is any other parts from the K25 that would be an upgrade? ie - power steering box, brake booster. I also noticed the K25 has a front swaybar but the K5 does not. Should I keep the swaybar? Thanks for any advice, fellas!