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post #1 of (permalink) Old 02-24-2008, 08:38 AM Thread Starter
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need help on doing full floater rear amc 20

hi need help info parts anything will help on doing a floater for my amc 20 on the scramber 1981 i have been looking on web and have found some items... one showned using the front hubs off mid 60s cj5 ... my problem is got new set of american racing alu ar23 wheels to replace the old cj steel wheels.... dont want to use anything that will change size or bolt patteren from the stock 5.5 on 5 size.... also i have another front complete axle off another 81 scrambler frame i used for parts can any of the axle parts off the dana 30 front end be used on the rear building the floater... would be cool if i can pull off the spare front hubs and use the lockouts along with the hub some all the wheels stay same... i still have the old 2 pc axle in the 20 and i dont plan on going into rocks and just mild off road big thing is will be doing alot of towing so sound like making rear a floter would be great just need to know what parts i need to get togther before i start project and how much mach work will i need to have done... if anyone knows about this please post thank you
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post #2 of (permalink) Old 02-24-2008, 06:58 PM
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This is a lot of Work

The Cheapest and easiest option is to find a Warn full float kit. Warn no longer makes them but you could find one use. New they cost about $700-800. The locking hubs are the weak point in these kits, they use hubs similar to those for a internal splined Dana 44 hub. However, these hubs are much weaker. Dana 44 outer shafts are 1.25" with 19 square (SAE) splines. However, the Warn full float axles are 1.313" with 30 involute 30 degree splines, This makes the ring that mates with the splines in the hub much thiner and due to the angle on the splines causes the ring to split. My buddy blowup 2 hubs with mild wheeling before going to drive flanges. Drive flanges are much stronger but are only available though warn and are about $200 a set. Ironically, the weaker hubs are about $115 and have way more pieces and much cost way more to make. Also drive flanges would need to be removed to get the wheels to free wheel for towing.

Okay, none of that really has much to do with your question.

There are no bolt on parts that will make a full float kit!! There are parts that maybe adapted. In your case it would likely make more sense to just get a full trailer.

In kind of a comedy of Errors I am building HDAMC20 full float rear axle. I did not plan on this project, I bought the axle then got an ARB for it then discovered that the axle shafts were toast. So rather then do the easy thing and get new shafts I used it as an excuse to make a home brew full float setup.

Since you wish to keep a 5 on 5 1/2 bolt pattern you will wish to use a mix of early 70's Chevy front spindles and 80's Ford hubs if you want internal spline hubs (search for information on switching a waggy front axle to 5 lug). Or CJ front spindles and hubs if you want external bolt on hubs. I am not sure what spline counts external hubs are available in so you will have to do some research. Internal Spine hubs are stronger and would be better for the rear but have weakness's in the locking hubs when using 30 spline shafts as explained above. You could use 19 spline hubs but hen the axle shaft would be weak. External hubs may or many not have stronger parts when using larger shafts but tend to loosen and break off the bolts that hold them on.

Okay, here is what I did. I wanted to have a Chevy 6 on 5.5" bolt pattern so I used parts from a 78 Chevy half ton Front axle.

The fallowing modifications were made to them.
1. Bore out the spindles to 1.35" so a 30 spline shaft will pass through.
2. Turn down the indexing ring on the spindle to fit in the Bearing Bore on the axle housing end.
3. Re drill the holes in the end of the housing to match the bolt holes in the spindles.
4. Make or buy axles, new custom axles would be about $500. I re splined some front Dana 44 axles.
5. Get drive flanges or hubs $200.
6. Setup Brakes. I had planed to use the front Chevy mounting brackets and calipers in the rear. However, the Calipers are so large that it would really mess up the brake proportioning. So I will need to find smaller calipers and may need to modify the mounting brackets, still have not got this completely worked out.

Some Pictures.

Boring the spindles on a lathe. Really needed a bigger lathe for this but it got the job done.

Bored out spindle on a 30 spline shaft

Turning Down the indexing ring on the back of the spindle to fit the bearing bore in the axle housing.

Back of the spindle after turning down. The Aluminum Puck was used to center the spindle using the tail stock on the lathe.

The Adapted spindle fits so snugly into the end of the axle that is takes a light hammer blow to seat and stays with out bolts

The end of the axle housing with new holes drilled. A plate will be needed to put a bolt in the top hole.

Splining the axles. This is a 54" table mill and you can see it is really not big enough the Dividing head (left) and the tail stock (right) both hang over the edge of the table. The dividing head is used to precisely rotated the shaft 1 29th of a rotation at a time to cut each of the 29 splines.

Here you can see the shaft half splined. I could not find a correct spline cutter with out getting one custom ground so I hand ground a 1/2" carbide endmill to give the needed angle of 94 degrees.

My buddy rotating the shaft with the dividing head to cut the next spline.

VICTORY!! First try the side gear slides on with very little slop. Could not ask for better I grinned like and idiot for the next hour. The odd looking end was left on for ease of machining and will be cut off now that the splines are done.

Top: Original AMC20 shaft, with rolled splines.
Middle: Completed Shaft made from a Inner Front Dana 44 shaft with cut splines on the yoke end.
Bottom: Dana 44 Inner Front shaft with yoke cut off ready to be turned down and splined.

This was a lot of work to do and the project is far from over. But it has been a lot of fun. As you can see I did most of the work my self using machine tools at the school. I would not want to guess what it might cost to have this kind of work done.

Here are some links to other peoples Full Float Projects, that I found helpful in planing mine.
Homebrew Full Float 9 inch
Warn Scout Full Float
Warn CJ full float
Homebrew CJ full float


I will start using Metric only when the duodecimal system is adopted!!
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