Do I need to switch Proportioning valve?

[joeycj5]

1054711

I left a post on another forum, still dont have an answer. I am swapping out a Dana 30 front drum axle to a dana 30 disc. I can see the stock prop. valve, but do I need to switch to a disc brake proportioning valve, or will the stock drum-drum prop. valve work? :roll: [addsig]

 

[RayOvac]

1054714

Yeah man I'm pretty sure that the discs will need a new prop valve. One off of a YJ would probably work nicely for ya....(disc front, drum rear).[addsig]

 

[joeycj5]

1054775

Yea, I have a Master cyl/booster and prop valve off of a mid 80's wrangler. I just didnt know if it needs to be swapped or not.[addsig]

 

[Bounty__Hunter]

1054776

All you need to do is pull the front brake line from the master cylinder and remove a check ball. Some use a small screw to remove this, never done it but a friend did when he switched his '73 Commando over to front discs.[addsig]

 

[joeycj5]

1054784

You mean there is a check ball in the M/C? Where is it? I will try anything before switching over Prop valve.[addsig]

 

[Bounty__Hunter]

1054810

I was under the impression that as soon as you removed the front brake line, there was the check ball, in the master cylinder. I think it can be a pain to remove.

I just did an unsuccessful web search, and the only info I found was where somebody swapped Chevy discs onto a scout, and said the factory drum/drum master cylinder worked fine, with no changes.

I'll see if I can get some better info.[addsig]

 

[Bounty__Hunter]

1054862

Here's the deal. Remove the front brake line from the master cylinder. You will see the concave seat that the brake line sits in, in the master cylinder. Remove this with the appropriate size sheet metal screw. The check ball will come right out. Put the concave seat back in and reattach the brake line.

I talked to my Jeep Commando buddy, he is still running the stock drum/drum master cylinder with no modifications, with front disc brakes. No problems.

With discs, you want the fluid to go back into the master cylinder to release the caliper. With drums, the check ball keeps fluid in the wheel cylinders to keep the shoes close to the drum.[addsig]