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Amc 20 one piece axle and disc brake conversion

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Saz2686 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saz2686 Quote  Post ReplyReply Direct Link To This Post Topic: Amc 20 one piece axle and disc brake conversion
    Posted: Sep/01/2018 at 6:32pm
I covered a few things on a different thread. I want it all to be in one thread. Hopefully someone can find some of these pics useful.

My 73 javelin started life as a 304 with auto. This vehicle has a 2.73 open diff. I had a 401 built and mated it to a world class t5. It is now time to install more friendly gears.

I was lucky enough to find a 3.54 posi (code A axle stamp) close to home.

I am installing dr.diff one piece axles. I am installing wilwood 11" disc brake conversion kit

Dr. Diff and others strongly recommend removing the thrust button from the center of the carrier. Remove the four bolts. Pry out the carrier. REMEMBER the order of shims and reinstall accordingly. Remove the two clips that hold in the cross shaft. Slide the cross shaft and out falls the thrust button. Torque four carrier bolts to 105 ft lb.



After sanding, I painted the axle with por 15



Dr. Diff kit comes with green brand oil seal and sealed bearings. I installed the new oil seal with rtv around the outside as per dr diff. Closed face out, I drove the seal in with a piece of 2" pvc.





When converting to wilwood disc brakes, one must put on the parking brake/hub assembly BEFORE pressing on the bearing. Press on bearing, followed by retainer.



Dr. Diff makes the axles for the longest length needed. The right side (passenger side) is the longer length, and will not be cut. The left side needs a 1/2" taken off.

Will update as I progress



Edited by Saz2686 - Sep/01/2018 at 7:24pm
Scott - 73 Javelin. 401 engine. T5Z trans. 3.54 posi

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Post Options Post Options   Thanks (0) Thanks(0)   Quote needafasterAMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2018 at 12:04am
Just a couple observations, Not sure how you plan to drive the car.
Why you have it out , You should weld the tubes to the center section.
you should brace your spring mounts with a piece of steel from the outer edge to the tube.
You planning a Pos. track diff. ?
Good job so far.
74 AMX, 401
Viper spec T56 6 speed trans
Hydroboost brakes with rear disks from a Avenger
3:73 TG rear,now Trutrac with 3:15
A Turbo is in my future.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saz2686 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2018 at 6:19am
I have read about welding the tubes. The spring mount reinforcement makes sense too. It will not be a drag car. I will skip any extra mods for now. I am curious to learn if it will fail. I have the existing rear I can play with when this new one goes in. This rear end came out of a 73 javelin amx. I bought it from the second owner. He never changed gears and the original owner did not. According to an old service book he has, axle code stamp A indicates 3.54 posi trac setup..
Scott - 73 Javelin. 401 engine. T5Z trans. 3.54 posi

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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXFSTBK390 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2018 at 12:42pm
Thanks for posting. Nice work. This thread will probably be re-visited if I convert to one piece axles.  Good idea about welding the axle tubes. If you only had ac/dc stick electrode or Mig what rod or wire would be used to weld the steel tube to cast iron?  
Questions are powerful tools...what's in your toolbox?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saz2686 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2018 at 2:23pm
I saw this idea somewhere. Instead of fooling around with the factory rubber grommet and plastic barbed insert I drilled and tapped for a breather. Male by barbed fitting found at home depot





Scott - 73 Javelin. 401 engine. T5Z trans. 3.54 posi

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saz2686 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2018 at 6:28pm
Correction - the factory grommet was plastic, not rubber. I have little experience and knowledge with welding, sorry.
Scott - 73 Javelin. 401 engine. T5Z trans. 3.54 posi

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2018 at 8:52pm
Have shortened Ford 8.8's and welded the tubes to center so the welding process I use:
- Clean and clean again, no rust, oil or any other contamination
-  Preheat the center and tube to 250° F minimum
- Weld, stick, 3/32, E7018, 85 to 90 AMPS, 1/4 at a time 1, 3, 2, 4 quadrants and feather your starts each time. Weave and fillet with more to the center then the tube.
- Right after welding wrap with 6"- 8" of rock-wool insulation and let cool to near room temperature
- Chip welds and grind any high spots. Grind and repair any spots that show signs of porosity from contamination (if you prepped well then this won't be an issue)
- with a good level check for straightness. If you preheat, weld opposing quadrants and insulate after there should be no problems but always ensure
- inspect for cracks and hit with a hammer, a thud indicates there may be a crack in the center. That is from not preheating, taking too long weld or not insulating after the welding



Edited by Trader - Sep/02/2018 at 8:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/03/2018 at 6:18am
The trick to welding cast iron is to get it hot BEFORE you start to weld, then cool it off slowly. Wrapping with insulation or burying in a sand box takes care of cooling. One guy I know used an old kitchen oven in his shop for welding smaller parts -- warmed it up to 200-250 and stuck part in after welding. Also handy for powder coating.

You have to get it up to a dull red -- which should be in the 250-300 degree range. Just get it to start looking red, that's enough. The hard part is holding the two parts where you need them before starting to weld. Welding gloves and pliers or tongs, and usually a helper. You might be able to tack parts together before heating, but often the tack will pop off or apart as the metal expands when heated. If you do get a good tack make sure you weld over it after heating.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave Z Quote  Post ReplyReply Direct Link To This Post Posted: Sep/03/2018 at 6:55am
Differential center sections actually weld fairly easy. I don't think they are grey cast iron, my guess is probably cast steel.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Sep/03/2018 at 10:48am
The center section (Ford 8.8) may be a cast steel but it's composition does not like TIG or MIG which tend to introduce cracks even with a preheat. Grinding sparks indicate it's not steel like the tubes and not cast iron like an engine block, something in between.
I have only had good/consistent results when treating it like cast.
I see posts were they just MIG in one go round with only a preheat. But I've also see posts were this has failed.

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