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Rear Disc Brake Conversion Kit MD7789

Zell

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Hi All,

I'm working on the rear of my 74 Cuda (in the resto thread section) and am looking to convert the rear drums to disc breaks.

Has anyone used Kit No. MD7789 on classicindustries.com? URL here:

1974 Plymouth Cuda Parts | MD7789 | Mopar 8 3/4 and Dana 60 Rear Disc Brake Conversion Set with Parking Brake | Classic Industries

There aren't many details, would be great to know how easy the kit was to install, if it came with instructions, make/model of brake pads that would needed for replace in the future, etc.

Any help is appreciated. :)
 

azmoparboy

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Hi Zell, I have that same kit on my car, it is actually a kit from a Company called Right Stuff brake kits. Jegs sells that kit for $346 to your house. I installed both green bearing and that kit to my rear axels and they perform and looked just great.

hope this helps,
Steve
 

azmoparboy

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Hi Zell, I have that same kit on my car, it is actually a kit from a Company called Right Stuff brake kits. Jegs sells that kit for $346 to your house. I installed both green bearing and that kit to my rear axels and they perform and looked just great.

hope this helps,
Steve

Here is a look at my Challenger axel

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20151201_104831.jpg
 

Chryco Psycho

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I would check the Dr Diff system he has it sorted out so you can reatin the better tapered roller axle brgs & run rear disc .
the other thing to watch is sway bar clearance so of the calipers willl interfere .
if you are retaining the same axles the only difference in track width is the thickness of the rotor or drum on the flange .
 

azmoparboy

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The axels are used again and if there is any width change it would be so very minimal. And as far as green bearing go I have 8000 miles on my challenger and 12,000 miles on my Charger. The longevity of green bearings are constantly being debated, but both of my cars seem to be very happy with them installed. With that being said, I sometimes think that the drum brakes properly being maintained is just fine too. Everyone has to do and deal with the choses they make with their cars, I know I have. What ever you decide I’m sure it will be awesome.
 

Mopar Mitch

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The tapered bearing design (OE) is superior for cornering activities; if all the car does is generally go straight, then the flat design bearings (such as the "green" bearings).. are OK.

As for my concern with the track width change, my concern is that I have 10" wide rims and wide tires (275-45 series)... and my fender lips are already flattened/pulled... leaving only about 3/8" clearance to the flushed fender lip. So... maybe I'd have to modify the fender lips a little more with the rear disc brake setup. The race clubs that I race with allow modified fenders ... even full-flared fenders is desired.
 

moparmarks

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That kit and the one from MBM both use Cadillac calipers. Real popular with a lot of conversion kits for GM and Ford too. I have them on my Dart and my friend has them on his 70 Challenger and 70 Cuda. They are a pain to get the calipers adjusted but other than that they work good.
These are the MBM units on my Dart

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Pacoloco

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Do you have to change out your proportioning valve? if so, to what?

Thank you
 

moparleo

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Rear disc brakes really offer little/no benefit over a properly maintained rear drum set up. 70-80% of the braking is done by the front brakes. The main reason cars come with 4 wheel disc brakes is because of the manufacturers cost and simplicity on the assembly line. Fewer moving parts, no human adjustments needed, installed on the strut assemblies off site. Just 2 bolts and a brake line and they are in.
They do look nice and that is probably what most people buy the for looks.
Now if you had a real race car and did road racing where you are constantly on the brake pedal, there would be a benefit because of the heat dissipation and less brake fade at high temps. Not really every day driving.
 

Pacoloco

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Thank you very much, I have an original disc/drum setup but the MC and brake booster went missing so I had to order a new one. And before I order a $160 Proportioning valve from Classic Industries plus new drums, shoes and hardware, that rear disc setup seemed really nice for only $346.

(Classic Industries = $129 +13 tax + $26 shipping)

Thoughts?
 

Chryco Psycho

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I would do rear discs IF -
I can still use tapered roller brgs
The caliper doesn't interfere with the rear sway bar .
It doesn't change the position of the rear wheel as far as the offset is concerned .
The parking brake is easy to connect
The price is great @ $350 for everything .
I would use a Wilwood adjustable proportioning valve so you can dial in the braking balance .
 

Mopar Mitch

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I would do rear discs IF -
I can still use tapered roller brgs
The caliper doesn't interfere with the rear sway bar .
It doesn't change the position of the rear wheel as far as the offset is concerned .
The parking brake is easy to connect
The price is great @ $350 for everything .
I would use a Wilwood adjustable proportioning valve so you can dial in the braking balance .
DR Diff sells a RDB setup ~10.8" diameter that uses the tapered bearings... which I fully agree is the best bearing design (especially for lateral/cornering load).
 

Bret Schneider

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I asked Cass at DR Diff his opinion of the Green bearings a few months ago.

His response:
"I sell 4,000 Green bearings a year and I rarely see any problems.

Cass"
 

Pacoloco

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is changing the bearings really necessary?

i went with Jegs 630640/630642
Mopar 8 3/4 Rear End Disk Brake Conversion kit.

Didn't see anything about changing out the bearing???
 

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  • BRAKE CONVERSION.pdf
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Bret Schneider

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For some of the brake conversion kits substituting the Green (non-adjustable, sealed) bearing for the original tapered bearing is either optional or required. If your kit doesn't mention switching the bearings then it's probably not an option so no need to worry about it.
Which is better? Lots of opinions out there but the bottom line is both designs have a proven track record so chances are you'll never have a problem regardless of which way you go as long as the installation is performed correctly.
 

Pacoloco

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Awesome Bret, thank you kinda got worried I bit off more than I could chew!
 
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