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Trolley valve for trailer brakes

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My 2001 RD 688S tandem started life as a straight truck. I bought it as a straight truck and converted it to a tractor. As a straight truck the trolley lever would apply the brakes on the truck tandem. In converting it to a tractor I installed the tractor protection valve and the red and blue supply valves in the dash. Using one of our other tractors I did the plumbing for the red and blue supply valves just as it was on the existing tractor, grabbing air for the new valving from the supply line that was already supplying the yellow parking brake valve. The output from the red trailer emergency valve I ran to the tractor protection valve and I grabbed service air from the treadle valve from a port that had a plug in it. Nearest I could tell this was similar to the plumbing that was on our existing tractor. However now when you pull the trolley valve on the converted tractor all the brakes come on.

What do I need to do to just make the trolley valve work for the trailer brakes only?

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I can't answer your question but I have never seen a trolley lever apply brakes to truck. I believe you have some improper plumbing somewhere. I think you have to correct that issue first.

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Some straight trucks used the trolley brake. Mostly in dump truck applications. It was handy when paving. Left your feet free. I would think you could block the line going to your service brakes

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Remember if it's got a hood it's no good!

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Some straight trucks used the trolley brake. Mostly in dump truck applications. It was handy when paving. Left your feet free. I would think you could block the line going to your service brakes

I have never seen that but can't say I disagree with the logic. I hooked the front axle to the trolley brake once on a old lousville I drag raced was great for staging and burnouts.

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Some straight trucks used the trolley brake. Mostly in dump truck applications. It was handy when paving. Left your feet free. I would think you could block the line going to your service brakes

Used to drive a single axle R tow truck that was plumbed this way. Trolley valve applied the drive axle brakes.

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I traced the trolley plumbing- (3) 3/8" lines, one supply, one exhaust and the delivery port goes to some, I would assume, check valves connected to the treadle valve. From there I'm not sure how the system works.

Jim- thanks for the diagram.

I will have to go back to our other tractor and look closely at the trolley plumbing. Before I use this truck with a load I want to be sure its right.

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My tandem axle dump has the trolley brakes on the rear axles. I'm gonna have to replumb it also cause I'm putting a pintle plate on so I can tow a tag trailer.

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my RD rollback is set up that way too,found out by accident,I didn't realize I had bumped it down and couldn't figure out why the truck wouldn't move

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Jimmy

my WAG sez the 1st trolly valves were on trains

more than likley made by Bendix ( before it became BW Bendix Westinghouse)

WotSezU

cya

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straight trucks had trolley set to rear service brakes through the treadle valve. when it's  set up for trailer operation' the treadle valve HAS to have a shuttle valve installed.  lt's a small valve many times threaded in to the treadle valve. more like a Tee -valve. some have brake light switch also. when foot brake applied, inside shuttle internally blocks air to trolley; likewise pull trolley applying  trailer brake ; tractor brakes not applied.  without shuttle valve  every time foot brake applied. air would exhaust through trolley . in your case every time trolley applied   truck service brakes come on 

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On 2/17/2016 at 12:24 AM, Bbpools said:

My tandem axle dump has the trolley brakes on the rear axles. I'm gonna have to replumb it also cause I'm putting a pintle plate on so I can tow a tag trailer.

install the shuttle valve.  challenge is to remember the trolley WON'T  hold the dump truck it self any more

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