Model year mix-n-match - brake proportioning

[kishy]

Hi
I would like to eliminate the brake combination valve (e.g. proportioning + dual system) located on the frame rail of my '85. It is reasonably straightforward to do this on my other Ford products, as there are known model years where the functionality of that valve moved into the master cylinder, so you just swap to the specified year master, replumb the car, and done. This is proving a little more complicated to figure out for the Ranger and I'm wondering if maybe someone here will know the right combination of model year parts to get me where I want to be.

I have already figured out that various 1990s years seem to have gotten rid of the combination valve, and front brake splitting was moved to the left hydraulic hose connection, but those years also seem to have RABS, and I'm not sure how critical the RABS valve is to proper drum brake proportioning/residual pressure functionality (that is, the RABS valve might be doing more things than just ABS).

What's throwing me off, looking at various years master cylinders, is that there does not seem to be any sort of thread-in valve that attaches to the master for the rear lines up until 1998. This is what makes me suspect the RABS valve is critical to proper proportioning on those model years.

Example: 1995 Ranger, non-cruise:

Normally, I would expect to see a large threaded hole for the rear line, like the following '91 Crown Vic:
(the large hole is not for a line, but for a valve that looks like a long nut, and the line then threads into that valve)

Compare that to a 1998 Ranger:

where we see that it does use a proportioning/residual pressure valve.

Have I answered my own question and the correct answer is to use a 1998 non-cruise master?


To state my goal clearly:
I want the rear line to exit the master, and be uninterrupted before it reaches the rear axle flex line.
I want the front line to exit the master, go to a simple splitter with no valving, then feed both front brakes.
The master needs to incorporate all system valving functions.

 

[Uncle Gump]

I've done this before and just used one of these under the hood with the existing master cylinder.

JEGS 63022: Adjustable Proportioning Valve | JEGS

Buy JEGS 63022 at JEGS: JEGS Adjustable Proportioning Valve. Guaranteed lowest price!

www.jegs.com

I know it isn't exactly what you're looking for... but it does work.

 

[kishy]

I've done this before and just used one of these under the hood with the existing master cylinder.

JEGS 63022: Adjustable Proportioning Valve | JEGS

Buy JEGS 63022 at JEGS: JEGS Adjustable Proportioning Valve. Guaranteed lowest price!

www.jegs.com

I know it isn't exactly what you're looking for... but it does work.

Yep, that would do it...but maybe not the direction I want to go.

I talked to a guy with an 87 (very unmolested truck, high confidence it's as-built) and he verified that 87 uses the newer style master (plastic reservoir with low fluid level switch), 2 lines out. One line goes to a simple splitter for the front brakes, and the other line goes directly to the rear, no valves or other blocks at all on the way.

So at the very least, an 86-90 (inclusive) master should do the trick.
A new master was introduced partial year 1990 which has metric fittings, but might (might) have the same valving. I found one of those for stupid cheap new, so I'm going to try it and see what I get. If the 90+ (looks like 90-94) master gives me too much rear bias, something inline will get me where I need to be. The only reason that might happen is if, as I suspect, the RABS module is also doing some pressure modulation for proportioning purposes.

Between eliminating the combination valve and replacing my drum backing plates (shoes hang up on severely rusted/worn metal), this should fix a couple of brake complaints I've had with this truck over the 5 years I've owned it.


Update in 2021:
I did end up going ahead with this, but forgot to update this thread. I don't see any value in bumping the thread so will just do this as an edit.
I used a 90-94 master cylinder, Fenco NM2532, which enabled me to delete the valve on the frame and run an uninterrupted line to the rear, and a simple splitter for the fronts.
At the same time I overhauled many aspects of the brake system including new backing plates, new front pads, new booster, and new lines for the entire truck.
The truck stops absolutely fantastic now and bias feels spot-on perfect. I do not believe that the master cylinder change had a lot to do with the new brake performance, but I really dislike working on systems that have the combo valve on the frame, so I was pleased to be able to get rid of it.