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Dana 70 disc conversion
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Below is the link to the thread. I'm not the best computer guy, so I hope I did the "cut and paste" thing correctly. If not, let me know and I'll tell you how I found it.
https://www.turbodieselregister.com/forums/archive/topic/128867.html
https://www.turbodieselregister.com/forums/archive/topic/128867.html
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"There was a thread posted several months ago on the disc conversion and most people who had it done were not happy with the outcome. Most reported that the pedal was VERY low and VERY soft, like it was severely air bound, only it wasn't. No matter how many times the system was bled (power bled, or manual) the low mushy pedal wouldn't go away. "
Well this raises a question that I would ask of anyone that might shed some light here. My Low miles 93 has very poor brakes even after ALL new parts on the rear (previous owner) and bleeding by me on a couple of occasions. It seems that the ABS unit at the back over the axle on the frame is not purging and in the All Data there is a special tool mentioned that no one (at Dodge) can seen to come up with. So how do you bleed the ABS. And has anyone simply taken the cussed thing out and tossed it in a privy pit where it belongs.
I will be reporting on the result of that very soon as I plan to do just that. I also intend to see if there is one size larger wheel cylinder for the rear so as to increase the pressure on the existing brake set. I am also very suspicious that the poor function of the rear brakes has something to do with those situations where the front gives continuous problems of warped rotors that is the result of over working the front brakes.
An earlier question regarding the reservoir capacity can be handled thus. Drill a hole in the partition between the two chambers about half way from the bottom and that will provide the additional volume to each axle and will still leave enough to provide a dual system in the event of failure of one or the other wheel cylinders. This will require that the master cylinder be VERY carefully cleaned (vacuumed maybe) after the drilling as the debris would kill the plungers. Someone may know of the correct unit that might be a bolt on to do the same thing.
James
Well this raises a question that I would ask of anyone that might shed some light here. My Low miles 93 has very poor brakes even after ALL new parts on the rear (previous owner) and bleeding by me on a couple of occasions. It seems that the ABS unit at the back over the axle on the frame is not purging and in the All Data there is a special tool mentioned that no one (at Dodge) can seen to come up with. So how do you bleed the ABS. And has anyone simply taken the cussed thing out and tossed it in a privy pit where it belongs.
I will be reporting on the result of that very soon as I plan to do just that. I also intend to see if there is one size larger wheel cylinder for the rear so as to increase the pressure on the existing brake set. I am also very suspicious that the poor function of the rear brakes has something to do with those situations where the front gives continuous problems of warped rotors that is the result of over working the front brakes.
An earlier question regarding the reservoir capacity can be handled thus. Drill a hole in the partition between the two chambers about half way from the bottom and that will provide the additional volume to each axle and will still leave enough to provide a dual system in the event of failure of one or the other wheel cylinders. This will require that the master cylinder be VERY carefully cleaned (vacuumed maybe) after the drilling as the debris would kill the plungers. Someone may know of the correct unit that might be a bolt on to do the same thing.
James
"Mad Max"
TDR MEMBER
I think can shed some intel into the master cylinder issue.
My hot rod, a 71 Dodge Demon, is a 440-powered 4-speed, scary, big dog kids-run-away kind of machine. It's very fast and stupid and makes me feel 19 every time I drive it. When I did the big block conversion I also knew I had to upgrade the brakes, so I did 4-wheel discs to it too. At that time the conversion kits were really darned expensive so I searched for alternative methods, and I ended up fabricating my own system, and to this day it still is the best stopping car I have ever owned (okay, my new Magnum may be juuust a bit better
). BUT, here's what I did, and I'm still surprised as to how simple it was.
The older A-body's can be converted to big bolt discs, and with the right caliper hangers you can upgrade the spindle to accept the huge 12" rotors from like '76-78 C-body's (Fury/Polara/Monaco/Charger, etc). So, my 71 Demon has '74 Dart big bolt pattern spindles and '78 Fury rotors, hangers, and calipers.
The rear is a piece of art. While rummaging through the candy stores (a. k. a. junk yards) I noticed the front rotors from an Eagle Talon looked like they would fit the old school Mopar 5-on-4-1/2 bolt pattern, so we took the rotors and calipers, opened the stud holes a hair, bolted them together and jigged them in place, and fabricated caliper brackets and welded them right to the axle tube.
So, the fronts are '78 front discs, and the rears are '91 Eagle Talon front discs, and here's the magic piece of the puzzle: The master cylinder and booster are from a '79 Dodge Diplomat... . front disc/rear drum car (the M/C is the aluminum one witht he plastic reservoir with two caps... and it doesn't leak) and I am not using a factory proportioning valve - the brakes are straight up, right off the M/C. I do however, have a pro-valve, but it is a good Wilwood unit and it is plumbed in with the rear line. So it's essentially just master cylinder and calipers - period. And, I race this car in autocross and SCCA events - the brakes are fantastic, and incredibly predictable. If I want to toss the car into a 4-wheel drift, no problem - either add gas or brake as needed. If I want to stoprightNOW I can actually feel the tires squishing trying to stop the car... and the rear brakes never seem to lock up unless the fronts are too. The fronts will lock up if in a serious turn and there is a little bit of off camber weight, but the brakes on this car are fantastic.
I'm planning to run the brakes on my Ramcharger... and my 93 Cummins, exactly the same way - no factory proportioning valve. I will run a manual valve, like a WilWood or LoKar valve to the rear lines, only to limit the pressure in the event the rears try to lock up.
The other piece of experience I can add is this - If you look in my readers rigs you'll see the big dog crew cab I built from scratch. I had to literally built the entire truck from scratch, including the entire brake system. The front end was a Dana 60 dually with discs (from a 79 1-ton), and the rear was from a 76 motor home with drums. I because of the Demon's brake success I also used the same M/C from a 79 Diplomat but used a new booster from a 1-ton truck, and folks I'm here to tell you that that big arse 7500 lb rig would put you through the windshield if you weren't strapped in, and lock up all 6 wheels on command. It had phenomonal brakes, way better than I thought a rig that big would have. With the trailer and a big load, say, 15,000 lbs gross, I never had brake 'concerns' while trying to slow down or control the load. It did however have the factory pro-valve, so since the system worked so well I just left it alone.
So, the executive summary to this book I just wrote, maybe the answer to a rear disc conversion is two/fold: Master cylinder and pro-valves. For the M/C specifically the ones from the later 79 and up cars and trucks (I'm assumming the cars and trucks share the same two-piece aluminum bottom/plastic top with two caps). , and for the valves, remove and ABS stuff in the system (my 74 PW had no ABS, just a factory valve). I have a feeling that these big rigs of ours are limited from the factory in the brake department, and I have a feeling that maybe the M/C's and 1st gen ABS valves may... may... be part of the problem. Yeah our diesels are heavy, etc etc, but brake pressure is brake pressure, and my PW was not a light truck.
So anyways, for my current project (my '78 Ramcharger XD-440), what I'm planning to do is this: convert to rear disc w/ park brake, remove factory valve, install Wilwood valve with rear line, use the very same booster and M/C from my '74, and try that out. For my '93 Cummins, it'd going to have the big honkin' dana 80, and it also has discs, so I'm going to use a similar system as the '74 and my '78 RC. We're actually looking to upgrade TJ's brakes on his '93 the same way, just without the rear discs - just M/C and booster, and make sure the vacuum pump is working.
I'm convinced there is a 'cure' for the rear disc conversion to make them scary good... we just gotta keep trying options and documenting them, then posting them right here.
Wow... . can I write a book or what... ...
... . my fingers hurt 
- Mad Max
My hot rod, a 71 Dodge Demon, is a 440-powered 4-speed, scary, big dog kids-run-away kind of machine. It's very fast and stupid and makes me feel 19 every time I drive it. When I did the big block conversion I also knew I had to upgrade the brakes, so I did 4-wheel discs to it too. At that time the conversion kits were really darned expensive so I searched for alternative methods, and I ended up fabricating my own system, and to this day it still is the best stopping car I have ever owned (okay, my new Magnum may be juuust a bit better
). BUT, here's what I did, and I'm still surprised as to how simple it was. The older A-body's can be converted to big bolt discs, and with the right caliper hangers you can upgrade the spindle to accept the huge 12" rotors from like '76-78 C-body's (Fury/Polara/Monaco/Charger, etc). So, my 71 Demon has '74 Dart big bolt pattern spindles and '78 Fury rotors, hangers, and calipers.
The rear is a piece of art. While rummaging through the candy stores (a. k. a. junk yards) I noticed the front rotors from an Eagle Talon looked like they would fit the old school Mopar 5-on-4-1/2 bolt pattern, so we took the rotors and calipers, opened the stud holes a hair, bolted them together and jigged them in place, and fabricated caliper brackets and welded them right to the axle tube.
So, the fronts are '78 front discs, and the rears are '91 Eagle Talon front discs, and here's the magic piece of the puzzle: The master cylinder and booster are from a '79 Dodge Diplomat... . front disc/rear drum car (the M/C is the aluminum one witht he plastic reservoir with two caps... and it doesn't leak) and I am not using a factory proportioning valve - the brakes are straight up, right off the M/C. I do however, have a pro-valve, but it is a good Wilwood unit and it is plumbed in with the rear line. So it's essentially just master cylinder and calipers - period. And, I race this car in autocross and SCCA events - the brakes are fantastic, and incredibly predictable. If I want to toss the car into a 4-wheel drift, no problem - either add gas or brake as needed. If I want to stoprightNOW I can actually feel the tires squishing trying to stop the car... and the rear brakes never seem to lock up unless the fronts are too. The fronts will lock up if in a serious turn and there is a little bit of off camber weight, but the brakes on this car are fantastic.
I'm planning to run the brakes on my Ramcharger... and my 93 Cummins, exactly the same way - no factory proportioning valve. I will run a manual valve, like a WilWood or LoKar valve to the rear lines, only to limit the pressure in the event the rears try to lock up.
The other piece of experience I can add is this - If you look in my readers rigs you'll see the big dog crew cab I built from scratch. I had to literally built the entire truck from scratch, including the entire brake system. The front end was a Dana 60 dually with discs (from a 79 1-ton), and the rear was from a 76 motor home with drums. I because of the Demon's brake success I also used the same M/C from a 79 Diplomat but used a new booster from a 1-ton truck, and folks I'm here to tell you that that big arse 7500 lb rig would put you through the windshield if you weren't strapped in, and lock up all 6 wheels on command. It had phenomonal brakes, way better than I thought a rig that big would have. With the trailer and a big load, say, 15,000 lbs gross, I never had brake 'concerns' while trying to slow down or control the load. It did however have the factory pro-valve, so since the system worked so well I just left it alone.
So, the executive summary to this book I just wrote, maybe the answer to a rear disc conversion is two/fold: Master cylinder and pro-valves. For the M/C specifically the ones from the later 79 and up cars and trucks (I'm assumming the cars and trucks share the same two-piece aluminum bottom/plastic top with two caps). , and for the valves, remove and ABS stuff in the system (my 74 PW had no ABS, just a factory valve). I have a feeling that these big rigs of ours are limited from the factory in the brake department, and I have a feeling that maybe the M/C's and 1st gen ABS valves may... may... be part of the problem. Yeah our diesels are heavy, etc etc, but brake pressure is brake pressure, and my PW was not a light truck.
So anyways, for my current project (my '78 Ramcharger XD-440), what I'm planning to do is this: convert to rear disc w/ park brake, remove factory valve, install Wilwood valve with rear line, use the very same booster and M/C from my '74, and try that out. For my '93 Cummins, it'd going to have the big honkin' dana 80, and it also has discs, so I'm going to use a similar system as the '74 and my '78 RC. We're actually looking to upgrade TJ's brakes on his '93 the same way, just without the rear discs - just M/C and booster, and make sure the vacuum pump is working.
I'm convinced there is a 'cure' for the rear disc conversion to make them scary good... we just gotta keep trying options and documenting them, then posting them right here.
Wow... . can I write a book or what... ...
... . my fingers hurt - Mad Max
I did remove the anti lock valve on my 1990, I simply plumbed the brake line around it. It worked like a charm, the pedal was high and hard and the truck stopped like a champ, almost too good. Pick-ups by design have very little weight on the rear axle, so if I wasn't running with a good load it was real easy to get the rears to lock up, especially with a little rain or snow on the ground. I found it was best to keep the rears un-adjusted to prevent lockup, but then the emergency brake didn't work all that well. It worked, but you had to put it to the floor to get it to hold.
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My ABS sleeps with the other dregs at the bottom of the privy. I have never had as good response from the brakes. I plan to do the same with all my trucks. I disconnected the lines going into the ABS unit on the frame and with a couple of adapter fittings from NAPA, reconnected the lines together. Bled the system and voila.
As BHiggins mentions, if you drive with little or no rear weight, this may not be for you but it is definitely for me. I can now slide my rear duals. I can tell when the tires need less pedal and consequently I am now the ABS controler. It cost about a dollar for the fittings. No mods on anything else. Emergency brake works like originall since that's what it is.
There might not be enough tire contact with a 250 to work well in this configuration. You will have to decide for yourself.
James
As BHiggins mentions, if you drive with little or no rear weight, this may not be for you but it is definitely for me. I can now slide my rear duals. I can tell when the tires need less pedal and consequently I am now the ABS controler. It cost about a dollar for the fittings. No mods on anything else. Emergency brake works like originall since that's what it is.
There might not be enough tire contact with a 250 to work well in this configuration. You will have to decide for yourself.
James
pics and a question
If a picture IS worth a thousand words, you just wrote a very nice pamphlet on the installation. Super.
Have you checked to know that the welding on the tubes has not drawn the alignment on the axle from dead straight? I have in mind to do some similar work but felt that it might need to be done in a fixture.
James
If a picture IS worth a thousand words, you just wrote a very nice pamphlet on the installation. Super.
Have you checked to know that the welding on the tubes has not drawn the alignment on the axle from dead straight? I have in mind to do some similar work but felt that it might need to be done in a fixture.
James
"Mad Max"
TDR MEMBER
We thought about the heat shrinking/expanding of the axle, and to make it as minimal as possible I welded in 1-2 inch segments to not heat a whole side at a time. And plus, to be honest, there really wasn't anything we could do about it anyways so I just tried to reduce the size of the heat pattern.
- M
- M
"Mad Max"
TDR MEMBER
I've been out of the shop for nearly a month - lots of good things going on personally , and so the projects quietly wait in the dungeon until I'm good and ready to go back in. Last night a good bud came over and lent a hand - I needed the motorvation - helped me do the other side, and we swapped that side in about an hour. Getting the first side figured out (location of the caliper, trouble-shooting the rotor/stud issue, ordering new axle nuts and seals) took a couple weeks, and once that was all researched the other side took an hour. Nice when it works that way.
I also learned that this Dana 70's bearings are oiled with gear lube from the center section, not packed with grease and sealed from the center section. Didn't know that. Had to tip each side up to drain the lube over to the other side in order to pull the axle, otherwise I'd have had a lap full of 80-90. The 8-bolt axle flange has a seal that seals the axle flange to the hub face, and that is one of two seals that keep the gear oil from leaking out. Just an interesting side note in case anyone wants to pull axles on a '93 Dana 70. I did pack the bearings with grease before I reinstalled the hubs because, well, I could. I figure it couldn't hurt - kind of like break in lube. I couldn't reinstall the hubs and clean bearings without some kind of grease - just had to have something on the bearings - force of habit.
Makes me curious tho about the effects of the lube going from one side to the other when off roading - seems the fluid would flood one side of the diff and evacuate the other, but now that I think about it, the fluid drains out of the axle tube, way out on the end of the axle, drains out the end and down, coating the lower (gravity) side of the outer bearing, and eventually working its way through the outer bearing to the inner bearing, coating it, and then I guess the oil then has no where to go except... well... it can't go anywhere so it has to stay there bathing the bearings, ya? So it seems the only thing keeping the 80-90 from leaking out is the big honkin' inner seal just inside of the inner big bearing and the axle flange seal.
Does that all seem correct?
I think this system is called a full-floating hub. If this is incorrect please one of y'all set it straight. I like knowing why and how stuff works so if I go to work on it I know why and how to make sure it keeps working the way it should. I don't care who's right or wrong, so long as in the end we're all smarter and wiser , and that our gear keeps working.
- S
I also learned that this Dana 70's bearings are oiled with gear lube from the center section, not packed with grease and sealed from the center section. Didn't know that. Had to tip each side up to drain the lube over to the other side in order to pull the axle, otherwise I'd have had a lap full of 80-90. The 8-bolt axle flange has a seal that seals the axle flange to the hub face, and that is one of two seals that keep the gear oil from leaking out. Just an interesting side note in case anyone wants to pull axles on a '93 Dana 70. I did pack the bearings with grease before I reinstalled the hubs because, well, I could. I figure it couldn't hurt - kind of like break in lube. I couldn't reinstall the hubs and clean bearings without some kind of grease - just had to have something on the bearings - force of habit.
Makes me curious tho about the effects of the lube going from one side to the other when off roading - seems the fluid would flood one side of the diff and evacuate the other, but now that I think about it, the fluid drains out of the axle tube, way out on the end of the axle, drains out the end and down, coating the lower (gravity) side of the outer bearing, and eventually working its way through the outer bearing to the inner bearing, coating it, and then I guess the oil then has no where to go except... well... it can't go anywhere so it has to stay there bathing the bearings, ya? So it seems the only thing keeping the 80-90 from leaking out is the big honkin' inner seal just inside of the inner big bearing and the axle flange seal.
Does that all seem correct?
I think this system is called a full-floating hub. If this is incorrect please one of y'all set it straight. I like knowing why and how stuff works so if I go to work on it I know why and how to make sure it keeps working the way it should. I don't care who's right or wrong, so long as in the end we're all smarter and wiser , and that our gear keeps working.
- S
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Hub lube
Full floating it is. The lube can also escape around the pinion seal. I use a little grease on the bearings when I install the hubs. Good practice in my opinion. I fill the center section and then drive the truck to a steep left and then right incline to fill each hub completely. Recheck the center section and off to the (insert your own destination).
James
Full floating it is. The lube can also escape around the pinion seal. I use a little grease on the bearings when I install the hubs. Good practice in my opinion. I fill the center section and then drive the truck to a steep left and then right incline to fill each hub completely. Recheck the center section and off to the (insert your own destination).
James
"Mad Max"
TDR MEMBER
Well the good news is the RC project is still under construction - the bad news is the RC project is still under construction 
- It is going real well, slow but very steady, but unfortunately no new news. It'll probably be late spring when the rig is rolling, definitely ready for summer.
- Max
- It is going real well, slow but very steady, but unfortunately no new news. It'll probably be late spring when the rig is rolling, definitely ready for summer. - Max
Well, I was considering converting to discs... What spurred this was a wheel seal ruining the perfectly good brakes on the right side of a 95 2500 I just bought. The drivers side drum won't come off, even by putting it in gear(while on jack stands). I'm tired of messing with drums, but looking at the cost of disc, I'm looking at a minimum of 350-400 for ones with no parking brake, and over 1000 for some that do. I could put egr shoes and larger wheel cylinders for much less, and stop adequately. Hmm... decisions, decisions...
I just converted mine to rear disk a few weeks ago. I used the El Dorado calipers and pieced it together myself. I'm into it less than 400. 00.
I must say it is one of the best mods to my truck I have done. I did have the low, spongy pedal problem everyone seems to have. I ditched the stock 1 1/8" bore stock master cylinder for a 1 5/16" bore. Rear ABS valve is still there. Pedal is firm as heck, and my truck stops about 200% better than with drums. I also used a proportioning valve for a 2002 Dodge.
If I had known how much better the brakes would be with rear disk, I would have made it one of the first mods right when I got the truck.
I must say it is one of the best mods to my truck I have done. I did have the low, spongy pedal problem everyone seems to have. I ditched the stock 1 1/8" bore stock master cylinder for a 1 5/16" bore. Rear ABS valve is still there. Pedal is firm as heck, and my truck stops about 200% better than with drums. I also used a proportioning valve for a 2002 Dodge.
If I had known how much better the brakes would be with rear disk, I would have made it one of the first mods right when I got the truck.
desertrat, would you happen to have any pictures and part numbers for the work you've done? Did you make your own caliper mounting brackets or did you buy them? What is your source for the el dorado calipers? I haven't found a pair under about 250-300 bucks(including core charge). I was thinking the standard chevy 3/4 ton calipers would be fine if I had some sort of line lock device, I saw the Jamar(sp?) mentioned on Pirate4x4, but its around 280 bucks alone. This is a work truck so it needs to stay relatively low-cost, but braking is very important...
Edit: oops, I ran across this thread in a search, and didn't realize it was 1st gen only.
I wonder what parts would swap over between the 1st gen and 2nd gen Dana 70? Surely they're very similar?
Edit: oops, I ran across this thread in a search, and didn't realize it was 1st gen only.
I wonder what parts would swap over between the 1st gen and 2nd gen Dana 70? Surely they're very similar?
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Willys, I found my El Dorado calipers in a junk yard for cheap. I used them for cores, as they were trashed. The core charge is why they are so spendy anyway. I got my brackets off Ebay from user greatlakeoffroad. They are for a Dodge D60 rear, but they fit the D70 too. You can use 3/4 ton GM front calipers, but no cable E-brake. I am running a Dana 70 from a '99, nearly identical to the 1st Gen. D70 but 5" wider.
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