Poor braking

Ever try and plumb a gauge into the drive axle service chamber and see if you're getting the proper pressure?

I have a sneaking suspicion that maybe the Mack has a bobtail porportioning valve issue.

 

That’s what I’ll be trying first.

The truck is setup for pup trailers.

I’ve even been told by guys at the company that using the trolley valve puts more pressure to the rear brakes.

But I find that it makes no difference.

I find it odd that the service and spring brakes are weak at the same time.

This truck failed the road test for the new driver during the testing of the spring brakes.

I didn’t know the spring brakes were weak as I don’t drive the truck much at all.

It was driven by a guy that retired last year that always drove slow and easy and never complained so it was never looked at closely.

 

X2 on @AModelCat checking brake pressures between the axles. Gotta verify that first

 

Was this problem ever solved triaxle dump truck 357 exact same issue

 

As far as I can see, the original poster has never returned to this thread to give all of us a heads up if his truck was ever fixed.

 

The last time he (the OP ) was on TTR ....................2017.
I guess he won't be back.

 

He's still trying to get his truck stopped!

 

Hahaha man I don’t know if you’re joking but that’s funny



heck my truck is doing exactly like he was saying. changed foot valve going it felt spongey so I said heck that’s got to be it. Next going to to try relay valve. and the abs valve idk if it can make it do this? honestly I feel like my 96 without abs is the best stopping truck. just don’t hit the brakes on concrete in the rain with a empty tag trailer. mine 2004 feels like the only axle stopping it is the steer axle and triaxle it’ll smoke the tires. my rear drive is doing some stopping since the pads have worn completely out quicker than the front drive which has over half maybe 3/4 life left. heck this will be the second set of steer axle shoes in a year and a half and how often do they wear out on any truck never really. When you apply parking brake with the truck empty at 50 it takes atleast 300 foot to come to a stop. That is not normal iv put all new short stroke chambers on it. All new slacks on it scams all looked the same. Iv pit multple sets of premium shoes also all the drums have been done atleast once. The relay valve is a a r12 two 90s supply air two both chambers on passenger side and both chambers on driver side. I pulled the hose off and hit the brake pedal and it immediately start spewing air. Going to check all chamber pressures tomorrow. Literally the other 5 trucks I have you can rest your foot on the pedal literally hit it with your big toe 15 psi max and will bring them all to a normal stop. This 04 has no applied pressure gauge. Truck does have 4 3030 chambers on the rear it’s is a factory dump truck 20 steer 46 rear Eaton shoes all the way around. I’m lost as of tonight

 

If the s cams were in on the wrong sides the slacks would not click when backing off correct? They would click when tightening instead of clicking when loosening correct? there’s no click when the slacks are getting tightened and clicks when loosening. that’s how I explain the lefty loosey thing to my drivers if they ever have to do it.

 

Keeping this thread going to learn.