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  • July 23, 2019, 05:57:38 AM

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Author Topic: Rear disk brake conversion  (Read 549 times)

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Offline jebidia24

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Rear disk brake conversion
« on: March 04, 2019, 03:21:27 PM »
I am undertaking the much maligned Eagle rear disk conversion on the AMC 15/Dana 35 rear axle.  My plan was inspired by RallyEagle and his ex-Dean Blagowsky Eagle rally car.  On his car, which you can see on his restoration thread in The Shop area, a previous owner used a second set of eagle front disks and mounted them in the rear.  During this process (in which I am undertaking a complete rear-end overhaul) I am also changing the shock mounting and installing a limited slip differential.  I figured this would be a good process to document since, when I was looking for a guide to do this, I didn't really find anything very useful and others may want to do the same thing.  Also, it was important to me that I do not change the rear axle, I wanted to keep the AMC 15/Dana 35, mostly for simplicity.

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #1 on: March 04, 2019, 03:29:03 PM »
Since I am doing so much work and modifications to my eagle, I figured it would be easier to just take the rear-end out and put it on a pair of saw horses to ease of work.  FYI, my car is 6 feet up in the air on car stands while I am waiting to do my new trans/transfer case install.  The first task once on the stands was to remove the old and not entirely proper working drum brakes.

This is actually the rear-end and drums off my Spirit.  I didn't decide to start documenting my change over until after some of the work was already completed.  This rear is also a AMC 15 but smaller.

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #2 on: March 04, 2019, 03:36:41 PM »
Getting the drums off was quite the arduous task, but in the end they came off.  Afterwards I disassembled the rear drum system, which was in pretty bad shape.  I think the drivers side slave cylinder gave up the ghost.  Following the brake breakdown, the next thing was unbolting the axles from the differential/axle tube.  The AMC-15/Dana 35 used in the eagles uses the bolt in style axle, which is actually better in my opinion to the c-clip style.  The bolts are right behind the drum backing plate and are pretty easy to get removed.  Now, to get the axle out, I used an old trick where I put the drums back on in reverse and bolted them back in but I did not tighten them.  That way they acted like a slide hammer.  And viola, the axles come out no problem.


Offline jebidia24

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Re: Rear disk brake conversion
« Reply #3 on: March 04, 2019, 03:49:55 PM »
For this conversion, the drum backing plate has to come off.  Unlike the later AMC 15/Dana 35 rear ends, where the backing plate can be unbolted and slide off, on the eagles they ride loose (after being unbolted with the axles) and the axle hub has to be removed.  The axle hub is pressed on and secured with a castle but with a cotter key.

The cotter key comes out fairly easy but the castle nut (which likely never been removed) is a different story.  I had to put it in a vice and use significant heat to get it to loosen up.

To remove the pressed in hub, I kept it in the vice and used a large three prong gear puller to essentially push the axle out of the hub, which is the way it is shown in my eagle TSM.

This is from right before I finished unbolting the castle nut and put the gear puller on.

With the hub off, the drum backing plate sides right off.  It is important to not when the hub came apart, a series of axle shims which were being used to align the axles to the differential fellout.  These will probably end up being re-used so I organized them and put them in a labeled plastic bag.  I also did this with all the bolts, so I know where everything is when assembly time comes.

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #4 on: March 04, 2019, 03:56:17 PM »
Now the first issue to overcome, I was under the impression that the rear axle hub was smaller than the disk hub mounting hole.  It appears that the hub is a quarter of an inch larger.

You can see in this picture that the hub doesn't go all the way into the disk.  I will either need to see if there is a different hub I can use which will work with my axle or take the hubs to my machine shop and have them turn down the diameter.  The hubs are pretty meaty, so I can probably have some material taken away and still be ok.  I also procured a spare eagle front steering knuckle assembly with the brake caliper carrier (which turns out to be kind of hard to find).  I will either cut the steering knuckle with the carrier mount down or use my spare from my spirit and weld them directly onto the axle tube as the caliper mounting point.

Offline rollguy

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Re: Rear disk brake conversion
« Reply #5 on: March 04, 2019, 06:29:33 PM »
When I did a rear disc conversion on my SX4 years ago, I had to turn down the wheel flange to fit inside the rotor. Even with the larger GM rotors I was using (same rotors that were used on the front Dana 44 from a full size Cherokee), I had to reduce the size of the flange. The great thing about the Eagle (and AMC in general), many GM parts were used. That makes it easy to mix-and-match cheap and readily available parts when modifying these cars......rich
1980 Eagle Turbodiesel Wagon (only 2 known to exist as of 2008)- 7-7-2011 Flight to it's new nest @ Rambler Ranch
1983 Eagle Wagon  Tan over Copper
1982 Eagle SX4 "ALTREGL"  (avatar photo)
1982 Eagle 4 Door Sedan  Copper over Satin Black
1985 Eagle Sport Wagon October 2007 ROTM (SOLD)
4 Biofuel powered Benzs ('98 E300, '82 300 CD, '82 300 TD (wagon), '80 240 D)
1983 GMC Van (6.2 Diesel)
1985 Mitsubishi pickup (2.3 Turbodiesel)

Offline eaglefreek

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Re: Rear disk brake conversion
« Reply #6 on: March 04, 2019, 11:21:27 PM »
Several years ago, I was screwing around in a junkyard and found some rotors from a Chrysler that slid right on. It's been so long, I can't remember which model. It was a FWD model, so probably the Concorde. But not sure if the rotor offset will work on the Eagle
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
1981 AMC Eagle Wagon As Seen On TV  Lost In Transmission


 

"I know he'd be a poorer man, if he never saw an eagle fly,
Rocky mountain high"  John Denver
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Offline RallyEagle

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Re: Rear disk brake conversion
« Reply #7 on: March 05, 2019, 06:35:17 AM »
Good work Jebidia24. Once the rear hubs are figured out, people can convert to rear disk brakes.  I believe my hubs are a factory stock item but from what vehicle is yet to be determined. 

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #8 on: March 05, 2019, 07:25:43 AM »
I think I'm going to have the hub turned down by my local machine shop.  The eagle hub has a lot of meat on it which I can spare.  If i thought I could find a replacement hub that had the right spline count, I would go that route.

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #9 on: March 18, 2019, 01:18:18 PM »
I was able to buy a set of 1980 Eagle front hub assemblies with the caliper carriers attached on ebay.  The caliper carrier can be a difficult item to find.  These need a little clean up, but should work great.  Now the question is where to cut up my spare front wheel bearing housing to make a bracket, just build a bracket, or use my smaller spirit set?  Also, the machine shop I was going to use to turn down my rear wheel hub is either out of business or closed for the season.  So now I am trying to find a different machine shop or find a Dana 35/ AMC 15 rear hub assembly for a bolt on style axle which is 1/4 and inch smaller but still has the 5x 4.5 bolt pattern.


Offline eaglefreek

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Re: Rear disk brake conversion
« Reply #10 on: March 18, 2019, 06:21:06 PM »
I don't see any mention of what year your Eagle is, but in case you don't know, 80-81 Eagles use different calipers than 82+.
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
1981 AMC Eagle Wagon As Seen On TV  Lost In Transmission


 

"I know he'd be a poorer man, if he never saw an eagle fly,
Rocky mountain high"  John Denver
Click for Fayetteville,TN Forecast" border="0" height="100" width="150

Offline RallyEagle

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Re: Rear disk brake conversion
« Reply #11 on: March 18, 2019, 06:35:08 PM »
Jebedia24,

The rear axle hubs on my rally car are stamped on the backside:
LR=  32361
RR=  23513

Perhaps this means something to someone.  They appear to NOT be machined down hubs.

Ted

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #12 on: March 20, 2019, 08:12:05 AM »
RallyEagle,
I appreciate you finding the casting by number (I assume that's what this is) for the hub.  I will see if I can find the part.  I would rather not turn down my hub, if for no other reason, make it easier for others to replicate.

Eaglefreek,
My SX4 is a 1981, and the parts I bought are from a 1980.  I was aware of the brake redesign in 1982 which made this find even more fortunate. 

Offline jebidia24

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Re: Rear disk brake conversion
« Reply #13 on: May 13, 2019, 08:14:00 AM »
So it has been a little while since I got any work done on this portion of the project.  I work in the power generation business, so spring time is hard for me to have any free time.  Anyway, after having zero luck in finding a machine shop that was willing to turn down the my rear axle hubs and even less luck finding a definite solution to axle or hub replacement, I finally got a break but I had to take a fairly expansive chance.  After searching the internet to what felt like its end for M15/Dana 35 rear disk kits, I found TSM.  TSM offers a rear disk brake setup for non c-clip dana 35 rear ends (Kit# 2562-35+).  They have them advertised for fitting 1986-1989 Jeep XJs and MJs.  I contactacted TSM to discuss AMC Eagle application and they reassured me that bearing any unknown complication, with the setup I have this kit should fit.  So I took a chance and bought one.  The kit was not inexpensive but the price wasn't terrible either (about on par for most rear disk conversion kits I've seen).  I really wanted to make a usable template out of somewhat readily available parts for other to follow but the need to get the project finished took priority.  So I received the kit, and have so far been quite impressed with the parts and resources available.  The only snag I ran into (so far), is that the axle hub brake drum centering stub was less than 1/32 of an inch too big for the disk to slide on.  This is shown below.

This was a fairly easy fix, the brake rotors just needed a little hand grinding to make the rotors fit.  I don't know if this is a slight difference in parts or just an acceptable casting error difference.  Now the rotors fit well.

So far I a quite pleased and this gave me the room to move forward with the rest of my M15/Dana 35 rear end performance rebuild (installed Dana 35 Traction-Lok differential).  Next is to finish some metal work on the axle tubes and the rest of the rear disk setup will be ready to be installed.  I will keep this thread updated regarding the ease of use of this kit for other to possible use as a sorted out application for the often confusing AMC Eagle rear disk upgrade.

Offline vangremlin

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Re: Rear disk brake conversion
« Reply #14 on: May 14, 2019, 08:37:17 AM »
Thanks for sharing that info on the rear disc brake kit. That is an awesome upgrade!
1981 Kammback 258 - "Pepe"
1980 Coupe 258 - "Ginger
1972 Gremlin X 304
1978 Gremlin 4 cyl 121 - sold
1964 TBird 390 - sold

 

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