So,....

My 93 W250 came to me with no ABS valve, 3/4" slave cylinders and 3" shoes,
The brakes were beyond useless, the rear end locked up before the fronts even engaged.

After a long and arduous search I located a functional ABS valve, now the rear brakes engage, lock up, and the ABS valve disengages the rear brakes and then the fronts engage and bring the vehicle to a stop. Oddly (to me!) the rear brakes never re-engage, I would expect them to pulse in and out...my fathers 92 pulsed the brakes.

It seems to me the rear brakes are far too effective, I am reluctant to install a inline proportioning valve (just because I'm **** stubborn) I want brakes that are effective in all circumstances (loaded or not)

Currently the brakes work well if the truck has even a light load (800 lbs +)

I assume that reducing the 3" shoes to 2.5" shoes would help,

Would swapping the 3/4" bore slave cylinders to 1 1/8 bore Chevy slaves reduce the braking force to the rear wheels as it would take more fluid from the master rear reservoir to apply the same pressure.....in the same stroke that is filling the front calipers?

Or are there calipers (part #'s please!) that require less cc's to fill and allow them to work faster than the rear slaves?

 

To follow up on the previous question I see there are 3500 lb axles and 4500 lb axles.
Will the calipers interchange and do the reservoirs have different capacities?

 

Different calipers for sure. The light axle uses the common Dodge calipers. The 4500# (Dana 60) uses the larger Bendix calipers also found on many years of 1-ton Chevies.

AFAIK, the master cylinder is the same on the Dodge regardless of the which caliper (providing it is a 250/350 truck).

The 1-1/8" wheel cylinders take even more fluid to apply, and apply more pressure than the smaller cylinders.

 

Sounds like you have a master cylinder issue, or there is a chance that some previous owner has the brake circuits reversed.

The front brakes are on the circuit closest to the brake booster (big reservoir) and the rears are on the circuit farthest from the booster (small reservoir). As the pedal is pushed the fronts activate just a hair sooner than the rears.

As far as the master cylinder: the smaller axle (3500# Dana 44) used the aluminum cylinder with the plastic reservoir, and the bigger axle (4500# Dana 60/61), which was the only option for both W250 and W350 Cummins equipped trucks, used the cast iron cylinder.

The smaller caliper will not fit the larger axle without major surgery only to give you dismal braking performance.

Good luck. Keep us posted.

 

I'm not sure booster or master an 8-lug Dana 44 uses... but each of my D250's use the Dodge calipers and iron MC as a factory paring.

 

That is interesting. I have never done a brake job on a 2wd CTD 1st gen Dodge. I learn something new every day....

 

"The 1-1/8" wheel cylinders take even more fluid to apply, and apply more pressure than the smaller cylinders."

The question is;
In the same amount of travel that it currently takes to fill the calipers, would the larger volume of the Chevy slaves fill completely, or would the larger volume result in a defacto pressure drop until more pedal was applied?

I will double check the plumbing and ensure the circuits are not reversed.

 

I run my 90 W250 with no ABS valve, factory slave cylinders and the 2 1/2 inch shoes and the truck brakes good empty or loaded. Not new truck good by any means but way better then when that ABS solenoid was hooked up. Don't think 3 inch shoes and the larger cylinders constitute an upgrade in these trucks. Just my opinion though.

 

If your brakes are fully bled, then everything is full of fluid.

A larger wheel cylinder (piston) moves less distance per pedal stroke, but with greater force. There's Dodge 1-1/8" wheel cyls too.

I'm reaching here, but I suspect the larger cylinders need the shoes to be adjusted tighter to work well.

 

Something’s screwy here. Most of those trucks had been upgraded to the 3” shoes, for increased longevity. I’ve upgraded many myself and they never seemed to make the rear brakes more reactive, so I would tend to eliminate that as an issue. I’m not sure if the 3/4” wheel cyls are proper for that truck, but they sound really small. Hope you get it figured out.

 

The lines are not reversed,
The shoes currently have about 1700 miles on them so the "tooth" of the drums should be slicked off to a fine polish.
Barring running the truck with a significant load, its almost unusable. The rear brakes lock up almost as fast as they are applied.


Does anyone have any notions on why the don't re assert themselves after the initial release?

 

Did you perhaps put the shoes on backwards? There is a leading shoe which should be on the side towards the front of the vehicle and a trailing shoe which should be on the back. It's been so long since I've been into drum brakes so I can't tell you which shoe is which but the Dodge manual should have this info or the shoes themselves should say.

Edwin

 

The short shoe goes toward the front......Ben

 

The trailing shoe is pierced for the e-brake lever and the leading shoe is not.......

 

Do the front brakes bleed well? Do they blow fluid on the inner fenders when the bleeders are cracked open or just dribble out?