AMC Eagle Den Forum

The Shop => Suspension, Steering, Brakes, Wheels & Tires => Topic started by: Blip Downshift on March 04, 2019, 03:21:27 PM

Title: Rear disk brake conversion
Post by: Blip Downshift 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.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
(https://i.ibb.co/wB3Xxs4/20190302-125312.jpg)
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.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
(https://i.ibb.co/TWx0Sbg/20190302-125454.jpg)
(https://i.ibb.co/ZWYxWtV/20190302-125511.jpg)
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
(https://i.ibb.co/ckvhGfS/20190302-133347.jpg)
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.
(https://i.ibb.co/yhgdsb0/20190302-135617.jpg)
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.
(https://i.ibb.co/6NCzj0m/20190302-135245.jpg)
This is from right before I finished unbolting the castle nut and put the gear puller on.
(https://i.ibb.co/48s7FY3/20190302-125542.jpg)
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.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
(https://i.ibb.co/X5TjBGV/20190303-145904.jpg)
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.
Title: Re: Rear disk brake conversion
Post by: rollguy 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
Title: Re: Rear disk brake conversion
Post by: eaglefreek 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
Title: Re: Rear disk brake conversion
Post by: RallyEagle 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. 
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
(https://i.ibb.co/p3XNwCd/20190309-123923.jpg)
(https://i.ibb.co/PY8vphq/20190309-123930.jpg)
Title: Re: Rear disk brake conversion
Post by: eaglefreek 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+.
Title: Re: Rear disk brake conversion
Post by: RallyEagle 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
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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. 
Title: Re: Rear disk brake conversion
Post by: Blip Downshift 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.
(https://i.ibb.co/6D7LKTt/20190512-145727.jpg)
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.
(https://i.ibb.co/6gwccvD/20190512-145853.jpg)
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.
Title: Re: Rear disk brake conversion
Post by: vangremlin on May 14, 2019, 08:37:17 AM
Thanks for sharing that info on the rear disc brake kit. That is an awesome upgrade!
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on July 26, 2019, 08:02:02 AM
Well, after a vacation, a new vehicle project, and some extensive body repair on the eagle, I'm back on this project.  I got the rear end performance upgrades finished and remounted in the car and I am now ready to fit this brake kit.  And that's where the proverbial wheels fall off.  I do not know if TSM sent me the wrong kit or if it just doesn't fit but..... it doesn't fit.  The instructions that came with the kit say "Dana 44" on them.  When I received the kit, I just assumed (first mistake) that all the kits were the same and TSM saved some money by using their most popular instructions for some of the less popular models.  All the parts are in good order but the mounting ears are not only the wrong size to fit over the axle tube but the mounting holes are also in the wrong locations.  It is noteworthy to state that this kit is designed for the Dana 35 and I am trying to fit it to a M15 (although one is just an evolution of the other).  So it looks like I will have to fabricate my own mounting ears using the TSM one as a template out of 5/16ths inch steel.  After that it looks like the kit will work as designed. Below is a layout of the parts that came in the kit.

 (https://i.ibb.co/mv9ng2Q/20190723-175557.jpg)
Title: Re: Rear disk brake conversion
Post by: Murdoc1905 on May 14, 2020, 09:46:51 PM
You said you installed a Dana traction-lok differential, do you have the part number or link to this? Was it specifically designed for the AMC 15 or was it for the Dana 35 and just happens to fit?
Title: Re: Rear disk brake conversion
Post by: kcinenoel on December 21, 2020, 06:31:37 PM
I put the disc conversion on the Rally Eagle rear axel when I owned the car.
I used front Eagle rotors and calipers.  I am a welder and cut the mounts seen on the axel.
I cut the backing plate off the axel. With the axel out of the rear I used my bench grinder to turn down the hub.
I used 2 Eagle inner pads  with the caliper. With the axel and cut down rotor back in the rear I mounted the caliper on the rotor and put brake pressure on it to center it on the rotor.  I tacked the mount to the rear and then welded it.
I did not have money for exotic arts all were junk yard parts.

Nick
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on February 16, 2022, 04:52:03 PM
Well after remodeling my house during the pandemic I am back on this project.  I got the brakes test fitted this weekend and I am pretty sure I know how they will need to go together.  This kit is well built but the differences between the M15 rear-end and the dana 35 this is made for has caused some complications that required modifications.  More on that later.  Also, I would really like to try to find a way to upgrade the rear axle shafts for chromoly non c-clip axles for the dana 35 but I'm not sure I can make it work.  I'm unfortunately pot committed on using this rear-end (for now) but it would be a shame to not upgrade every part possible.  I know it's said that this can't be done, but I wonder if I can fit eagle axle bearings on the D35 axle shaft to make if work?  I'm not sure if anybody has actually tried or just gave up on it and did something else before they bought parts.  I may buy a used 84ish D35 axle shaft off ebay to use as a trial.
Title: Re: Rear disk brake conversion
Post by: maddog on February 16, 2022, 07:17:56 PM
I have a Dana 35 in eagle eyes my 1980 wagon and if I remember right the part numbers for the wheel bearings were different and I think the ones on the Dana 35 are actually a larger diameter but I'm not 100% sure on that. if the weather is not too bad this weekend I might try to get to the yard and see if I can't get a wheel bearing off an XJ and see what size the difference actually is between that and the M15 bearing I have.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on February 18, 2022, 09:13:37 AM
Thanks maddog, that would be great.  And Murdoc1905, I will get the information for you and I can post a picture of the completed install.  Sorry for the delay, I hadn't worked on this in awhile.
Title: Re: Rear disk brake conversion
Post by: maddog on February 20, 2022, 09:20:03 PM
Well the part numbers are indeed different and the Dana 35 bearings are 2.252 in. on the outside diameter and 1.401 in. on the inside whereas the M15 bearings are 2.329 in. on the outside and 1.25 in. on the inside.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on February 22, 2022, 08:23:53 AM
Bummer, well I appreciate you looking.  Looks like I will stick with the M15 for now.  I will probably end up upgrading to a different rear-end in the future but right now I'm going to press on with what I have.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on February 22, 2022, 08:43:23 AM
Well after test fitting the setup numerous times, I can now say that, although TSM made a great kit for the Dana 35, it does not fit the M15.  Even with the original TSM D35 caliper bracket support modified for the M15 axle tube and mounting configuration (at least the way I modified it) the caliper bracket to rotor configuration is crooked.  It's so messed up the upper brake pad retention pin hits the side of the rotor.
(https://i.ibb.co/6txnVVG/20220220-143913.jpg) (https://ibb.co/6txnVVG)
(https://i.ibb.co/cvxS3F5/20220220-143929.jpg) (https://ibb.co/cvxS3F5)
So I decided to make this kit work no matter what I do.  That being said, I do have a 3'x3' piece of 1/2" carbon steel.  So I decided to make my own caliper bracket support.  The first thing I did was to make a carboard template.
(https://i.ibb.co/jR5ZDD2/20220220-144008.jpg) (https://ibb.co/jR5ZDD2)
Then I cut out the size of steel I needed from the larger piece and mark it for cutting.
(https://i.ibb.co/LDTLWc4/20220220-143953.jpg) (https://ibb.co/LDTLWc4)
(https://i.ibb.co/hWTZX35/20220220-144002.jpg) (https://ibb.co/hWTZX35)
(https://i.ibb.co/YhfNpRg/20220220-145904.jpg) (https://ibb.co/YhfNpRg)
Next was to break out the plasma cutter.  Although it takes some effort, my plasma cutter was capable of cutting the plate to the shape I wanted.  From here it will require some considerable cleanup.
(https://i.ibb.co/4FJwKmj/20220220-154447.jpg) (https://ibb.co/4FJwKmj)
I may have melted one of my old plastic saw horses while I was at it.  I cleaned up the part using a grinding wheel and marked and drilled the holes in there appropriate positions.  I test fitted it and it did fix the caliper bracket position problem.  More photos to come.
Title: Re: Rear disk brake conversion
Post by: maddog on February 22, 2022, 08:42:31 PM
Not a problem. If you do end up changing rear ends one thing to consider about the Dana 35 is that the pumpkin is offset so both axles are different lengths and the whole axle is actually about an inch shorter on each side, but on the plus side you can swap your ring and pinion from the M15 into it and keep your current gear ratio. The other rear end that a lot of people like to use is the 8.8 out of a Ford if you go that route you will have to find the correct gear ratio for it to be able to keep your existing gears. Now I don't know what modifications are required for the 8.8 but for the Dana 35 all I had to do was grind the welds to the shock mounts and swap them to the opposite sides of the tubes and it was a direct bolt in after that.
Well after test fitting the setup numerous times, I can now say that, although TSM made a great kit for the Dana 35, it does not fit the M15.  Even with the original TSM D35 caliper bracket support modified for the M15 axle tube and mounting configuration (at least the way I modified it) the caliper bracket to rotor configuration is crooked.  It's so messed up the upper brake pad retention pin hits the side of the rotor.
(https://i.ibb.co/6txnVVG/20220220-143913.jpg) (https://ibb.co/6txnVVG)
(https://i.ibb.co/cvxS3F5/20220220-143929.jpg) (https://ibb.co/cvxS3F5)
So I decided to make this kit work no matter what I do.  That being said, I do have a 3'x3' piece of 1/2" carbon steel.  So I decided to make my own caliper bracket support.  The first thing I did was to make a carboard template.
(https://i.ibb.co/jR5ZDD2/20220220-144008.jpg) (https://ibb.co/jR5ZDD2)
Then I cut out the size of steel I needed from the larger piece and mark it for cutting.
(https://i.ibb.co/LDTLWc4/20220220-143953.jpg) (https://ibb.co/LDTLWc4)
(https://i.ibb.co/hWTZX35/20220220-144002.jpg) (https://ibb.co/hWTZX35)
(https://i.ibb.co/YhfNpRg/20220220-145904.jpg) (https://ibb.co/YhfNpRg)
Next was to break out the plasma cutter.  Although it takes some effort, my plasma cutter was capable of cutting the plate to the shape I wanted.  From here it will require some considerable cleanup.
(https://i.ibb.co/4FJwKmj/20220220-154447.jpg) (https://ibb.co/4FJwKmj)
I may have melted one of my old plastic saw horses while I was at it.  I cleaned up the part using a grinding wheel and marked and drilled the holes in there appropriate positions.  I test fitted it and it did fix the caliper bracket position problem.  More photos to come.
[/color]
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on February 28, 2022, 10:00:50 AM
OK, after some modifications to the part I built, I finally got this thing together.  Below is a photo of the part I built mounted to the new TSM caliper bracket.
(https://i.ibb.co/10XK8S0/20220226-130914.jpg) (https://ibb.co/10XK8S0)
Here are some photos of the final test assembly.  I apologize for my shop being so messy.  When spring comes around, there is going to be one heck of a cleanup.
(https://i.ibb.co/18vBZ3Q/20220226-145901.jpg) (https://ibb.co/18vBZ3Q)
(https://i.ibb.co/WvhP0QM/20220226-145914.jpg) (https://ibb.co/WvhP0QM)
(https://i.ibb.co/zHX6sx4/20220226-145922.jpg) (https://ibb.co/zHX6sx4)
The next thing is to take it all apart, again, transfer the completed part cutout and hole diagrams to a new template and paint the new pieces for rust protection and to give the project a finished look.  Then the rear end can go back in the car and I can lower off the stand and check the new ride height.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on November 04, 2022, 09:05:55 AM
Well, the brake system works but as posted before there was some serious modification.  So it looks like this kit is not an easy bolt-up job.  Unfortunately, in the process of getting this all together, I took apart one of my two piece axels and cannot get them back together in a manner than gives me any confidence.  This looks like the catalyst for yet another rear-end change.  If I could, somehow, get one-piece M15 axels then this could still work but as far as I know, such parts do not exist.  I may do a AMC 20 swap, possibly a Ford 8.8 as suggested earlier, but I will probably buck the normal trends (as this is going to be a street car) and go with an IRS setup out of an 80s Jaguar XJ6 or XJ12.  They have a 3.54 gear ratio with LSD and have already been fitted to other AMC vehicles.  Look for future posts as this idea gets fettled out. 
Title: Re: Rear disk brake conversion
Post by: vangremlin on November 04, 2022, 11:23:26 AM
Well, dang, that's a shame that you did all that work and will now have to go a different route.  Let us know which one you go with and update us on your progress.
Title: Re: Rear disk brake conversion
Post by: Blip Downshift on November 07, 2022, 08:33:37 AM
If I can find away to use what I have, I will continue this project, but it doesn't look hopeful.