The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Rebuild 1972 K10 12 bolt or swap in 14 bolt Semi Float or Full Float

fishmunger · 05-23-2020, 04:18 PM

I got this 1972 K10, 350, auto, currently has original axles and 4.56 gears (open) front and rear. It's lifted 4" and has 35" tires on 15x10" 6 lug mags. Other than that, it's a pretty original truck, and I'd kinda like to keep it just the way it is. I like the vintage 6 lug mags in came with and want to keep them.

I'm fixing the truck up to be a daily driver/work truck. I'd be towing a 3500# boat around pretty regularly, and occasionally a 6000# boat. I'd also like it to be a fun off road trail truck, but not for crazy rock crawling. I 'plan' on keeping all 4 wheels on the ground and trying not to smash up the body.

I definitely want to have those detroit truetracs installed front and rear, and possibly change the 4.56s to 4.10s to get better mileage.

In my mind, the path of least resistance is to have both axles rebuilt at a shop when I have the truetracs and/or gears installed. I'd probably upgrade to aftermarket beefier 12 bolt axles at this time. This would also keep the truck original, which is maybe a good thing value-wise (and the fact that it's held up for almost 50 years this way)?

But it seems that the consensus on the internet is that putting money into a 12 bolt is stupid. So I've read a lot about swapping to a 14 bolt semi float or full float too. Sounds like the semi-float is the way to go if I want to keep my 6 lug wheels. If I went this route, I'd probably find a 14 bolt SF and then have the same shop rebuilt it and move the perches or whatever is necessary to make it fit.

I plan on leaving the front axle alone (other than rebuilding, gear swap, trutrac).

Concerns are:

Is the 14 bolt semi float 'that much stronger' than a rebuilt 12 bolt with upgraded axles? Is it necessary for my needs? Do 12 bolts break that easily?

Other than moving perches/shock mounts, am I going to run into other problems swapping the semi float in place of the 12 bolt? Since I don't plan on doing the work myself (can't weld), complications add $$. I worry about things like the E-brake, driveshafts, u-joints, etc adding up in a hurry.

Will my 15x10" wheels fit over the drums on a 14 bolt?

It sounds like the 14 bolt SF came in 2 widths? What would be ideal?

Alternatively, if I went with a FF axle, could I just run wheel adapters to fit my 6 lug rims and be on my way?

Appreciate all your opinions guys, thanks in advance!

05-23-2020, 04:18 PM	#1
fishmunger Registered User Join Date: Jan 2005 Location: CA Posts: 411	Rebuild 1972 K10 12 bolt or swap in 14 bolt Semi Float or Full Float I got this 1972 K10, 350, auto, currently has original axles and 4.56 gears (open) front and rear. It's lifted 4" and has 35" tires on 15x10" 6 lug mags. Other than that, it's a pretty original truck, and I'd kinda like to keep it just the way it is. I like the vintage 6 lug mags in came with and want to keep them. I'm fixing the truck up to be a daily driver/work truck. I'd be towing a 3500# boat around pretty regularly, and occasionally a 6000# boat. I'd also like it to be a fun off road trail truck, but not for crazy rock crawling. I 'plan' on keeping all 4 wheels on the ground and trying not to smash up the body. I definitely want to have those detroit truetracs installed front and rear, and possibly change the 4.56s to 4.10s to get better mileage. In my mind, the path of least resistance is to have both axles rebuilt at a shop when I have the truetracs and/or gears installed. I'd probably upgrade to aftermarket beefier 12 bolt axles at this time. This would also keep the truck original, which is maybe a good thing value-wise (and the fact that it's held up for almost 50 years this way)? But it seems that the consensus on the internet is that putting money into a 12 bolt is stupid. So I've read a lot about swapping to a 14 bolt semi float or full float too. Sounds like the semi-float is the way to go if I want to keep my 6 lug wheels. If I went this route, I'd probably find a 14 bolt SF and then have the same shop rebuilt it and move the perches or whatever is necessary to make it fit. I plan on leaving the front axle alone (other than rebuilding, gear swap, trutrac). Concerns are: Is the 14 bolt semi float 'that much stronger' than a rebuilt 12 bolt with upgraded axles? Is it necessary for my needs? Do 12 bolts break that easily? Other than moving perches/shock mounts, am I going to run into other problems swapping the semi float in place of the 12 bolt? Since I don't plan on doing the work myself (can't weld), complications add $$. I worry about things like the E-brake, driveshafts, u-joints, etc adding up in a hurry. Will my 15x10" wheels fit over the drums on a 14 bolt? It sounds like the 14 bolt SF came in 2 widths? What would be ideal? Alternatively, if I went with a FF axle, could I just run wheel adapters to fit my 6 lug rims and be on my way? Appreciate all your opinions guys, thanks in advance!