Disk brake question

I installed a newer dana 30 with disk brakes under the front of my 1974 CJ5 do I need to change the proportion valve? It has a manual master cylinder but it is original for the Jeep. If I do need to change it what year should I get one for?

 

Yep, you need the one for disc brakes. Power or no power doesn't matter. Need the valve. Think you need the master from disc too. With drum brakes the piston and reservoir are the same size. Disc brake the res and I think piston are bigger on one chamber.
76 and up.

 

I used the master cylinder for a 78 CJ with manual disk brakes on my 72. The depth of the piston was fifferent so I had to shorten the push rod about .400

 

I did the same thing except i swapped out the push rod with the org. 73 one.

I also used a adjustable proportioning valve.

 

Thanks for the help. I also have a couple other questions does anyone have pictures of the stock master cylinder and pro. valve I believe mine might be swapped in. Also how do I tell what year the calipers I have are from to order my brake lines they are 2 bolt in the caliper brackets with 2 bolts holding the caliper to the bracket.

 

there are differing opinions on this. i converted my front drums to later cj discs, but retained the original '75 master cylinder, which has equal size reservoirs. i also used the original valve. the only modification i performed was to remove a rubber residual pressure valve from the front brake line where it exits the master cylinder. these were used to maintain some slight pressure in the brake lines for the drums, but aren't desireable for disc brake action. i've now had this setup for over 2 years, and have no complaints. the brakes work better, especially after getting muddy or wet.

 

Ist picture is a 1974 CJ Proportioning valve

2nd picture 1983 CJ prop valve . Font manual disc brake

 

I ran this set up for a while but I noticed that i was going through rear shoes like no other. The rears ended up doing most of the stopping force until i swapped the master cylinder out and added the propositioning valve.
Just something to check on.

 

Don't mean to hijack the thread, but mine has a Dana 44 with discs in the front and the factory rear with drums. My jeep stopped sweet when I first bought it, then the rear hardline started to leak at a fitting. I replaced it, bled the lines, and nothing seemed to work. I took it to the mechanic, and he put a new master cylinder in, but now the jeep stops good, only after I pump the pedal once, then the brakes work normal after that. So what's the deal? He is a tiny bit perplexed, and we are still working through it. Do I need Herm's Dual master cylinder or a proportioning valve (actually not sure if I have one, so do I need a new one or mine replaced with different style?) or do my front calipers retract too far and are faulty or what? Anyone have any ideas on this? Jeep just hasn't been the same since that line broke, makes no sense...

 

if you only have to pump once, and the pedal doesn't "fade" after that, your rear shoes may need adjusting. if they are too far from the drum, the first pump provides the contact, the second provides the braking.

 

The first provides the contact, the second provides the braking you say....So does nothing really happen with the front discs in that if the drum pads don't make solid good contact in the rear right away, the front discs don't really do anything toward applying braking force for stopping power yet either? If that's the case, why is that? I'd assume path of least resistance theory and all the fluid goes rearward towards the drums for the pad "take-up" with the first pump, then it's evened out for the next pedal push to get myself stopped? If anyone knows the actual science behind it or has another theory, let me know. I like to learn as much as I can about everything. Thanks.

 

If you're interested and you send me your addy I've got a couple of older text books we no longer use that explains brake systems in depth. Not from an engineering stand point but from a service, theory, and educational stand point. Pay shipping and they are yours.....