GM 14 bolt
AMC 20
This is a very heavy duty axle used in almost all Chevy 3/4 ton and heaviier applications from the mid 70's till present. It has 30 spline 1.5" axleshafts, though they neck down to 1.43" after the splines. This axle is a full floating design and uses the largest wheel bearings of all the axles I'm comparing. The ring gear is 10.5" in this brute and you pay for it in ground clearance. The 14 bolt and the dana 70 are comparable axles strength wise, though if the 14 bolts axle shafts were 1.5" all the way out it would clearly be the stronger of the 2.

There are a couple variations of this axle:
     a)full floating 8 lug single rear wheel
     b)full floater 8 lug Duallie
     c)full floater 8 lug cab and chassis
     d)semi floating 6 lug (newer trucks)

(a) is about 69" wide WMS toWMS
(b) is ?????
(c) is 63" wide WMS to WMS
(d) is about 69" WMS to WMS

(c) is perfect for a jeep. I have found them in duallie trucks that werent pick-ups. Trucks like armored cars, ambulances, motorhomes, stake beds etc.
they are hard to find, but worth it. The hubs are a bit longer than the standard 14 bolt, which is nice because it allows the use of the full width 14 bolt axleshafts.
Disk brake kits are available for the 14 bolts for about $300. this shaves almost 150 pounds off the axles weight. Pictured below is just such an axle.

The only real downfall is the sixe of a 14 bolt... you really need to run tires larger than 35" with this axle. Also, gear ratios do not get lower than 5.13

The newer 14 bolt (6 lug) have smaller ring gears and are semi-floating.
The AMC 20 was used in Jeeps from about 1976 till about 1984. The ring gear is 8 and 7/8" (slightly larger than a d-44) and the axle shafts are also slightly thicker than a d-44.

There are a couple variations:
     a)narrow 5 lug (CJ)
     b)wide 5 lug (CJ)
     c)waggie 6 lug

a) is about 56" WMS to WMS
b) is about 58" WMS to WMS
c) can be either 63 or 67" WMS to WMS

There are more differences. the CJ axles are much weaker that their full size counterparts. Its common to see a "spun hub" on these axles.. they are a straight axle shaft with a splined hub pressed on the end. Over time, the splines in the hub spin. This isnt a question. it WILL happen. The CJ AMC 20's also have weak axle tubes and are prone to warping. I have also seen several axle tubes break right out of the pumpkin. The Full size Jeep AMC 20 is a different animal. It has a flanged 6 lug axle shaft and thicker axle tubes. These units are fairly stout. It's common to see people swap them in because they have already spent the $$$ on gears and lockers for their CJ AMC 20. The CJ version can be made into a fairly reliable unit with 1 pc axle shafts available from several sources.

Gear ratios are available from 2.72-4.88
humvees use an AMC 20 center section still today and they have a good posi in them. ARB, detroit, lockright, no slip, are all available for this axle
Hosted by www.Geocities.ws

1