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Discussion Starter · #1 · (Edited)
Just thought I would shear my weekend Project. This HD AMC 20 is going under my YJ. Before I setup the gears I decided to shave it. Here is the housing uncut.


I decided to Remove about an 1 ½" of material from the housing this works out to cutting ½" below the bottom of the second bolt up on each side. This should net about 1 ¼" more clearance once the new bottom is added. The Plate seen bolted on below is to try to hold the housing from moving during cutting and welding. I measured between the bolt in the plate to find the change if any in size. I used every trick I could to prevent movement (the plate shown, Short welds, penning the welds as they cooled, lots of cool down time between welds) and still the bolts moved together by 0.013". I hope this will not cause problems. I have yet to set up gears so as long as the Carrier bearings are still parallel it should be okay.


Next I had to smooth the cut surface. Here is a trick that helps in finding High spots. Grind such that all lines are in the same directions in this case side to side. Then take a flat piece of steel that is oily and still has mill scale. Rub it on the surface perpendicular to the lines formed by grinding. This will leave oil on the high spots also the mill scale will slightly polish the high spots. The dark areas in the picture show are the high spots which can be easily seen and ground down.


Here is the bottom after welding an grinding.


Here you can see the inside. Even though I gained a 1 ¼" of clearance I did not take much from the actual room in the housing. Note I have yet to weld a bead around the inside or V-notch and weld the cover area.


Here you can see the old cover on the shaved housing.


Here it is done except for the cover. Note, the ring gear has about ¼" of clearance. The Tab attached to the bottom is for a bolt in the new cover. I am not sure what I want to do for a cover. I may just modify the old with a piece of flat plate, or I may make a new one out of 1/8" plate. I have even thought about Modify a Dana 60 cover as it is nearly the right size and would be easier then making a heavy duty cover from scratch.


Finally this was used in creating the new housing bottom. It is a 2 axis CNC Plasma cutter. All I had to do was cut card board to the shape and scan it into auto CAD. Then trace the Picture and send to the CNC. It then cuts out the part in about 40 seconds. The hole near the tip of the torch is the outline of the new bottom after the cut.


Sure I could have done it free hand but when you have access to toys you have to use them.
 
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Re: Shaving the AMC 20 HD (not very Dialup Friendl

I thought everyone had a CNC plasma cutter in their garage....right next to the tig welder and electron microscope.....

Impressive....I see nothing wrong with using the tools that are available to you....and lets all be honest.....free hand will not look nearly as nice as the CNC piece....

My only real comment about it is that it seems like an awful lot of work to gain 1.5".
 

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nice job.. did you use 1/4" for the bottom? if so, i'll warn you about it deflecting... but you should be good with 1/4" of clearance to the ring gear...
 

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Re: Shaving the AMC 20 HD (not very Dialup Friendl

Good job, and a great writeup! Soon I hope to be putting a HD 20 under my '7. If I decide to shave it I'll spread the bolts by 0.013" before I start with the hot glue.
 

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Re: Shaving the AMC 20 HD (not very Dialup Friendl

[ QUOTE ]
..My only real comment about it is that it seems like an awful lot of work to gain 1.5".

[/ QUOTE ]

Wowsers (My new favorite word)! I LIKE IT!

There have been lots of Jeepers who've done more exotic things (like lifts) to gain that 1.5 - 2" of clearance.

So, my question is... what was done to harden the axle housing?
 

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Discussion Starter · #7 ·
Re: Shaving the AMC 20 HD (not very Dialup Friendl

DDawg16:

Well I wish the CNC plasma cutter is not in my garage, for that matter I wish I had a Garage. It is acctually at the university Where I am getting my masters in Engineering. But, I have access and can use it and the milling machine and lathe for projects.

It deffineatly was alot of work. I figured it would take 4 hours and it took over 6. Ofcoarse I was helping a Friend cut and machine a bumper.

Yes, it only gains 1 1/4" but that is more clearance gain then switching from 33 to 35 inch tires.

jeepgod:

I used 1/4" plate for the new bottom. I am only a little worried about bending and don't think it will be able to hit the ring gear. The ring gear is at the edge of the cutout and about 1/4" above. I did not wish to get the plate to close both for bending and for oiling concerns. The Pinion bearings need the ring gear to sling oil from the bottom of the case and up the cover where it then goes down the top oil passage. If the bottom is to close to the ring gear it could lower the flow of oil and damage the pinion bearings. I also hope to make the cover act as a brace to the bottom edge to stiffen it. Also the New plate is 4130 grade steel which has a yeild strength of 75 ksi, regular mild steel has a yeild of 36 ksi. This should, I hope make the 1/4" plenty strong.

Jim_Lou:

Thanks for the kind words. The 0.013" of shortening was measured at the lowest remaining bolts. Sadly I did not think to take any measurments at the carrier bearings before starting. I am hoping that the shortening only effects the lower part of the housing and does not extend to the bearings. Even if it does I hope to be ok as many people take much more material out of Dana 60's and make no Attempt to track shortening and seem to get away with it. I can only assume that they have atleast that much length change.

LEVE:

The housing was not hardened. It is cast steel so regular filler rod works for welding. The heat effects you see in the picture with the cover on are the result of welding housing to the plate on the inside, not an attempt to harden. I am not worried about armor for the housing as I do very few rocks. The big reason for shaving is to get rid of the vertical ridge which runs around the lip of the housing. It hangs down about 3/4" below the original bottom and hangs up rather easy, Nothings worse then to almost clear a stump only to be hung up on the last 1" of housing. I plan to make a cover this weekend. I am trying to model it in AutoCAD to save time cutting plate. If I can creat patterns that fit together well, then they should be easy to shear as pictures that can be printed and cut.
 

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Re: Shaving the AMC 20 HD (not very Dialup Friendl

it sounds like you put some thought into this.. and it also dosen't seem like you will have a problem with that plate..

it looks nice.. and 1.5" of clearance for some work.. is well worth it..
 

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Discussion Starter · #9 ·
I just got a PM asking me to relink the pictures in this so I thought I would add to what was here as it was an unfinished writeup.

After many attempts to think of a good way of making a stronger but still reasonable sized and shaped cover out of flat plate; I just gave up and modified the cover. I cut the stock cover off at an angle so a flat plate could be welded to it.


I then took a small piece of plate and welded it to the end of a 3/4" pipe. Here the plate is clamped on the end of the pipe waiting to be welded all around. I really should have cut the plate smaller and put a chamfer on the end of the pipe to get better penetration with the weld but I think this will work.


I then ground down the outside of the plate on the plate on the pipe to give an even surface around the outside of the pipe. Then a 5/16" hole was drilled in the center of the plate. Sorry no picture here but It will become clear shortly.

I then welded a tab of plate to the center of the bottom of the housing to be later tapped for a 5/16-18 bolt like the other cover bolts. The welds seen here are kind of light, they were added to after this photo.


The hole in the welded tab was then tapped and a cover bolt installed through the inside of the pipe hole the the pipe to the tab. This picture is kind of close up but hopefully the idea is clear.


A cardboard pattern was then cut to fit around the pipe while laying against the cut edge of the cover.


The cardboard pattern was then used to cut a chunk of flat plate. A magic marker is then used to mark the surface of the plate onto the pipe. Hopefully this picture makes the previous ramblings make sense.


The pipe is then cut off as marked and chamfered on the outside, and the slot in the plate is chamfered on the inside. The resulting v-notch is then welded up.


Here is another picture after the weld is ground back flush and a little clean up of sharp edges has been done.


The plate is then welded all around to the cover.


After more then a year in which I was busy with other stuff including installing a locker, I had not yet installed all this in the Jeep. I got to thinking that this cover system needed some rethinking. As you can see in the photo below there is only about 1/4" of seal surface across the bottom of the cover and the potential to develop a leak is would be great.


I will continue what I did to fix this issue tomorrow if time allows. If the pictures do not show up please let me know.
 

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mods to amc hd rear end

hi looks good,,, question is this the amc 20 that you are doing the full floating disk brake conv on ,,,, just wanted to know how that is going,,,,,getting a few more small parts together to get ready to install the full floater disk set up on the scrambler cj8 over the winter and wanted to know if you ran into any other problems on yours thanks
 

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Discussion Starter · #11 ·
Yes this is the same axle. I got it done and in the Jeep this summer, still needs shocks and the master cylinder needs to be just a little bigger, but other than that it is good to go. Only a couple of trips around the block with it though before I had to leave town for work. I am way behind on writing all this stuff up.

I will try to finish the cover writeup tonight.
 

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Discussion Starter · #12 · (Edited)
Okay now to wrap this up. I did not like the size of the lower seal surface, being only 1/4" wide I felt that there was a good chance for leaks. The best way to have fixed this would be to totally redesign the bottom plate and cover, but I was to far in now to really consider that. If I were to do this project again I would make the cover with a lip that went above the bottom plate and flat headed screws through the bottom plate into the lip on the cover.

What I did to improve what I had was to add a small lip inside the cover without screws. Since I wanted the lip to be welded to the cover but sit flush on the bottom of the housing I drilled 2 holes in the cover over the area where the tabs forming the lip would weld on. Then I held the tabs in place on the bottom of the housing using some small plastic magnets in the photo.


I then installed the cover and welded through the holes to the tabs to hold them in place. Then the cover was removed and the tabs full welded, and the welds cleaned up.


Another picture of the lip added to the cover.


I then felt that a truss would be a good idea. It is made from 2x2x1/8" box tube.


Since I am going spring over the truss stops at the spring perches. If I was spring under I would run it clear to the end of the housing.


The truss is attached to the top of the housing with some 1/4" flat stock and some welds. This is done to try to get the truss to for a composite beam with the housing to stiffen it more then just the truss itself.


One last picture of the truss completed. I waited till the axle was under the Jeep and weight on it before welding the spring perches.
 
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