The Stovebolt Site Forums The Parking Lot Big Bolts Dually Axle swap on a '46 1.5 T

Howdy All --- been digging through both the posts here and used parts yards for about a year now and it looks like I may have found a reasonable candidate to replace my buses dually rear axle.

Wanting to keep the original 20" wheels while having more gearing options makes it tricky, but from what I have seen and measured, a Dana 80HD just might do the trick. They came on '91 - '02 Chevy & GMC trucks and have the same 10 lug, 7-1/4" pattern as my bus but the center hole is a half-inch larger in diameter. That means boring out all my existing wheels to fit the rear, then making adapters so they will also work on the front. Not too scary and I have several spare rims, "just in case".

The newer axle is actually a 1-Ton, but is rated higher than my original. It also comes with big disk brakes, which is great, but also makes me wonder about how or if the stock disks & calipers might clear the old rims. Relocating the spring mounts seems the easiest part of the whole job but that too remains to be seen.

Size-wise, the Dana appears to be about 66-1/2" wms to wms while as near as I can tell, the stock rear end is about 66" so width should not be an issue.

These rear axles sell complete with brakes in the $1000 buck range here which seems pretty reasonable given that the Dana 80 has a solid reputation. And, they are commonly found with 4.63 gearing which would be just about a perfect match for my engine/tranny combo.

If anyone here has any wisdom, opinions or experience with this combination, I'd love to hear it before I jump off the deep end. Thanks in advance.

If you go to more aggressive brakes in the rear will cause the rear to lock up on slick pavement. You will need a proportioning valve to equalize the brakes. Otherwise you will find your back end passing you the first time you do hard braking on slick pavement.

Sounds like a good plan.

I have a Dana 70HD from a GM P-30 chassis, 10 lug, which is the very same at the wheels as the 80 you're looking at, the 22.5" wheels clear all the brakes stuff just fine and I expect the 20" wheels will as well. Remember the axles came with 19.5" wheels that clear.

Here's some reading about that conversion
http://www.stovebolt.com/techtips/bigbolts/p30swap/

And some reading about adapting disc brakes on the front if you like.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=725572#Post725572

You ought to be able to find an axle for under $1,000. I forget what I paid for mine but nothing near that, and later got one for a friend for the price of two rotors.

Grigg

Many thanks Grigg --- it was your very excellent series of posts that steered me in that direction to begin with. Any thoughts regarding the wheels clearing the calipers? The only Dana 80 I have been able to find locally so far was buried under a dozen other axles, so I never could get very accurate measurements. No idea what the outer diameter for the disk arrangement might be. Will continue the hunt though.

And roger the adjustable proportioning valve. Definitely part of the plan and likely the only way to ever balance out disks all around on this rig.

Your wheels will fit. As mentioned the original wheels on these axles in question were 19.5", so anything larger will surely fit.

Not all Dana 80 axles nor 70HD for that matter are the same, or even same width, or same bolt pattern either. The only version you'd be interested in will have the GM 10 lug on 7.25" bolt circle, assuming you still want to use original wheels. Also don't get confused by a Ford axle (F SuperDuty) with same bolt circle but with a larger center.

Grigg

Thanks again Grigg --- it is the GM/Chevy 3500 10 lug x 7.25 that I am looking at. Milling a quarter inch off the radius of the centers of the rims should not be too difficult. And as you noted, finding any specific measures is tricky. Lots of variants out there. I am going to an axle shop on Monday that rebuilds these units to get more precise measurements. Hope to be able to buy a rebuilt just for the sense of security it should afford. The shop came highly recommended.