high applied brake pressure

I had a FLD Freightliner that did that too. On that truck I could hook the blue and red lines together and it helped a lot. Must of been something with the valve

 

I'm sure you've checked for a leak, but if not, start with a leak-down test and if it is draining the tanks, chock the wheels, use a board or similar to block the brake pedal down and walk around checking for a leak or unusual loss of air.

 

Does it lock the rears when botail in the wet? sound like it might be an issue with the steer brakes not applying.

 

put a quarter between your glad hands a hook them together and push your red valve in on the dash for the trailer brakes. Some older trucks when bobtailing dont let much air go to the drives so all your braking is done wiyh the front.

 

You have a "brake proportioning valve"! Which IMO are dangerous and scary. They should come with new new shorts because you have to push extremely hard on the pedal to stop. We had one truck that came with one and it wasn't on there very long. Had a sticker on the dash warning of the increased brake pressure that was required while bob tailing. Here's a link to what it looks like (looks like a standard relay valve) and a description.

Only way to fix it is to block off the gladhands and drive with the red button in, or take that junk valve off and replace it with a standard brake relay valve. I'd just replace it since relay valves are pretty cheap usually between $20-$40 depending on which direction you need the ports (vertical or horizontal)

Here are 2 quotes from the valve description

Translation = You have to stand on the brake pedal to stop!

Translation = total BS, what it actually does is make your butt pucker!

 

Wow, sounds like what I have. I have a 69 White Freight liner tank truck converter to a strait truck. Trailer pintel hitch and glade hands removed. When I had a load I nerly had to stand on the brakes to stop going down a hill to make a turn. A real pucker factor. I notice what looks like a quick release valve on the back diff axle leaking air with the button pushed in to go. I don't think thats normal and will get a new one. The emergnecy air release buttons and resovor have been disconnect and don't function. I looked at the bobtail valve and wonder if I should install it.

 

i dont know if it will cause i am too nervous to drive on a nice sunny day let alone on wet pavement.


Where is your sense of adventure, you haven't had fun until you drift a bobtail up to a red light trying to stop.