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Installing Dr. Diff One-Piece Axles |
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CamJam 
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Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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 Topic: Installing Dr. Diff One-Piece AxlesPosted: Nov/11/2019 at 7:32pm |
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I have an axle that's slightly bent. Since the Dr. Diff single-piece axles are only $295 a pair I figured I might as well replace both of them.
I don't see any reason to remove the hubs from the old axles. Will I then need a puller to pull the axles out or will they come out easily once the backing plate is removed? Are there any C-Clips or anything else that holds the axle in place other than the backing plate? I do have a TSM and see no mention of it, which seems odd to me. I guess the pressed-on bearings against the backing plate must be what holds it all together. I also understand that the 71-74 Javelin use the longer Ambassador axles, so only one of the axles needs to be cut, 1/2" off with a chop saw. Does that sound right? TIA!
Edited by CamJam - Nov/11/2019 at 7:48pm |
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD  |
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tufcj
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Posted: Nov/11/2019 at 10:13pm |
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Once you unbolt the backing plate and brake line and unhook the e-brake cable, the axle and backing plate will come out as a unit. I just turn the brake drum backwards and thread on the lug nuts. Use the brake drum as a slide hammer and the axle will pop out. Once it's out, cut the cage that holds the roller bearings. With the rollers gone, the bearing race and backing plate will come off without pressing the axle apart. I have a set of the Dr. Diff axles for my AMX, but haven't installed them yet. I've heard that if you have a twin grip that you need to remove the spacer block from the center of the diff. Bob tufcj
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69 AMX
74 Javelin AMX 67 Rogue If you need a tool and don't buy it... you'll eventually pay for it... and not have it. Henry Ford |
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PHAT69AMX
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Posted: Nov/11/2019 at 10:34pm |
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Picture of the 2-piece "Spacer" instructions say to remove from the spider gear shaft in a twin-grip amc posi carrier when installing 1-piece axles.
Your existing backing plates have to be installed on your new 1-piece axles before the new bearings are pressed on, unless you modify, enlarge, the backing plate center hole. there is a YouTube Video where a guy how he did it. This is it that shows enlarging backing plate hole.... Remember.... AMC stands for... Ain't nothin' that's easy... !   Edited by PHAT69AMX - Nov/11/2019 at 10:42pm |
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CamJam
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Posted: Nov/12/2019 at 12:24pm |
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Ok, that tells me most of what I need to know, thanks guys. Looks like something I can tackle.
Great idea on using the brake drum as a slide hammer, Bob! I take it no shims are needed with the single piece axles, but how exact do I have to be with the length when I cut the axle(s)? What I mean is, does it need to be within tenths of an inch or thousandths?
Edited by CamJam - Nov/12/2019 at 12:27pm |
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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1970390amx
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Posted: Nov/12/2019 at 1:59pm |
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Unless you change carriers to a one piece early carrier your car will have a different thrust block. It can be removed by taking out the spider pin. I would do this. Cutting axles to short will limit engagement to the spider gears. With the thrust block out you can get away with cutting them a few tens of an inch longer and still be ok.
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1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box |
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bigbad69
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Posted: Nov/12/2019 at 8:33pm |
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Before you do any of what tufcj said, remove the big nuts retaining the hubs. Once you have removed the axles, trying to hold them stationary while you torque off those nuts will not be too fun. Instead, with wheels on the ground, use the inertia of the car to help hold the axles. Be sure to chalk the wheels, especially if you're using a breaker bar. Even if you're replacing the two piece hub/axle assemblies, you may want to separate the hubs from the axles some time in the future. There's always someone looking for good hubs. Edited by bigbad69 - Nov/12/2019 at 8:37pm |
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69 Javelin SST BBO 390 T10
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amcenthusiast
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Posted: Nov/13/2019 at 9:21am |
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1) Sorry to learn you're absolutely sure the axle is bent (commiseration)
2) Almost considering to remove link to Dr Diff on my website: I'm not an AMC axle specialist, but it's only logical that the spacer is there for a reason. It must be there for one axle to share it's side load with the other axle shaft, plausibly because the wheel bearings are tapered bearings? and the reason for shims on the driver side? -Should a non-tapered roller bearing be pressed on instead on a 'cut to length' replacement shaft? The AM 8 7/8" axles have their wheel bearing seals inside the bearing = they are 'permanently lubricated'... I have read articles about 'other make' rear axles having a similar design -and when it finally came time to overhaul the unit, there was consideration for how to install a grease joint for those who might want to give it a squirt of grease every now and then. -just an idea/while your at it. |
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Steve_P
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Posted: Nov/13/2019 at 9:48am |
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The thrust block is there so you can set the end play for the axle's tapered roller bearings. Most aftermarket axles use (sealed) ball bearings which you don't set endplay
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CamJam
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Posted: Nov/13/2019 at 1:45pm |
Yes, I have some visible wheel wobble. I removed the wheel and drum and measured hub runout. This was more than a year ago and I don't remember the measurement now, but it was obvious that the problem was with the axle or hub and not the wheel. Thanks for the explanation on the thrust block Steve. I had wondered why it was possible to remove it with single piece axles and assumed it must have something to do with the bearing. |
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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Heavy 488
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Posted: Nov/13/2019 at 6:19pm |
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You can have wheel wobble from a missing drum balance weight.
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amcenthusiast wrote: