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Tucker76CJ7 08-25-2005 11:52 AM

4 wheel drum lines...
OK, I think I might know why my breaks don't work very well...I've tried everything...

I noticed that the lines going from the MC to the Prop. valve might be wrong.

1. Should the lines go from the Front of the MC to the front of Prop.


2. Front of MC to back of Prop.

Remember this is a 76 CJ7 with 4 wheel drums....


Caver Dave 08-25-2005 05:24 PM

Re: 4 wheel drum lines...
Not sure why you'd have a prop valve in a drum-drum vehicle. Unless they changed the method of proportioning since the early '70s models (different sized wheel cylinders & sometimes line dia. between the 2 ends), you shouldn't have one. FWIW, the front lines (L&R) are usually split off a block mounted on the frame.

I have a virgin '72 parts manual and TSM at the house I can check if'n it will help...

Tucker76CJ7 08-26-2005 08:14 AM

Re: 4 wheel drum lines...
Agreed, I had known that there should not be a prop. with a 4-wheel drum setup...I was guessing that it did nothing and was only there for the break warning light.

I know that on a "front disk/rear drum" setup the front disks are run off the back port on the MC.

The real question is, Do 4-wheel drum breaks work the same? Front drums run off the back port of the MC?

On a side note, two other things are funny about my setup.

1. The front axle has been replaced (Still has the junk yard marks on it.) With one from a 78 CJ5. Maybe it really had disks to start with.

2. The MC has a larger line going out of the rear port. (I think it's the rear port)


John_Strenk 08-26-2005 09:07 AM

Re: 4 wheel drum lines...
THis is what the Combination valve looked like on my 76 CJ with 4 wheel Drums:
Look a lot like a Disk/Disk one doesn't it.

It has the proportioning valve to the rear to prevent locking up the rears before the front because under hard breaking, the weight will transfer to the front and with less load on the back the rears will lock up and you loose control. It also hase a safety valve that will block off the compramised side of the brake system incase of failure which allow you to use the remaining system to try to stop.

If yours looks like this:

Then I would suspect it was set up for disk/drum brakes. With the metering system going to the front it would make for some poor braking with drums.

These Combination valves are setup like this with a metering valve on the front for the disk brakes and a proportioning valve on the back.

There is also something special about the MC for Drum/Drum setup. I think they have a 1 way valve iat each outlet to prevent the springs from pulling the pistons back to far into the slave cylinder. Otherwise you would have to pump up the brakes each time to use it.

And yeah #2 was the way my brakes were run on my 76 drum/drum.

THe drum brakes on my 76 were fantastic and easily stopped my CJ5 on 33" wheels. Even got better with the flexible SS brake lines. They just sucked when they got wet. That's why I converted to a 79 Disk/Drum setup.

Tucker76CJ7 08-26-2005 11:43 AM

Re: 4 wheel drum lines...

I mean John_Strenk,

That's got to be the best post I have ever got back! That's not to say the others sucked...just that yours was REALLY GOOD! PIC's and all...Damn....

Thank you, I've got lots to work with and know a few of my problems already. (Can't wait to check the valve tonight...)


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