d30 / d44 axle swap brake questions

[smithflyfisher]

I posted this in the binder planet tech talk forum, but I thought the more info I get the better, so here goes.

Just got done swapping my d30/d44 setup to d44s all around. I changed lines, mc, prop valve, and installed new brake hardware. However, my front discs (which are manual), tighten up and reaalllly drag me down after driving for about a mile and will not release. I can depress the brake pedal and release the pressure by bleeding the fronts, then they operate correctly until I get out on the road. I can't understand it, the brakes work perfectly for awhile, and then the pedal gets tighter and tighter until I can barely depress it at all, and I have to really get after it in 1st gear just to get rolling.

I used the front and rear axles from a 1976 sii and the prop valve from a 1974 sii. The prop valve was from a Scout with power brakes. I'm really scratching my head on this one...... It took me and my buddy the whole weekend to swap the axles. Any help would be greatly appreciated!!!
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1972 sii, 304 3spd, 4" SUA extended
rear shackles, custom front winch bumper

 

[Michael Mayben]

A few things can cause this issue...

But I need more info and some clarification. You say your replacement front brakes are "manual", what do you mean??

Are you using a power brake booster and master cylinder that was a functioning system when you began this deal? Or are you using a non-power brake master cylinder now with no booster? Or a replacement power brake master for drums only with no booster?

Please describe exactly what the brake system consists of now, including which master cylinder is currently installed. I know you have swapped to disc brake system in front, but there were/are two different front caliper systems used, and it matters if the donor brake system was manual brake of power brake originally.

The earliest front disc systems did not use a proportioning valve, that function was handled through the installation of a rear brake (drum) companion system that had a smaller diameter wheel cylinder system in order to try and make the front/rear line pressure "compatible. That was not the proper way to achieve that and that system was obviously not used very long on production sii. But at this stage of the game, donor (and service part replacement) parts can be really scruud up when mixed and matched incorrectly.

I currently work with a bastardized s80/800 with sii axles, running disc brake front only with no power booster. The sumbitch works perfectly and the pedal pressure is hardly any more noticable than a stocker sii with a booster.

This kinda info has nothing to do with "year model"...but is broken out by chassis number (especially the prefix letter). So the donor chassis number goes along way to determining exactly which parts you are dealing with, same as for the chassis number for the vehicle under discussion for future reference. IH service parts list are referenced off chassis number, engine number, along with installed component codes, etc. Not by "year model".

If you can supply the detail, then we'll get into the diagnosis and fix without a lotta "I thinks" and "maybes" (we don't do "maybes" on the ihon forum)! And the two primary ideas I have for you are dependent upon a detailed description of your parts. I know what is happening, but how to overcome that is parts-dependent.

I'm moving your post to the "brake tech" sub-forum!