Brakes on Navistar

NEKS · Jul 30, 2013

Bought a single axle tractor and put a 35 foot tandem axle goose neck behind it to haul hay. It seems like I can not get the rear brakes to work as hard as they should. Its a 96 model and the front brakes are doing all the work. I was told that if you do not hook up the air lines to a trailer, its designed to restict the back brakes for safety. Is this right, so how do I fix it and where can I buy a operators manuel. Thanks

71INT · Jul 30, 2013

NEKS
What you say is true if your Tractor has
Bob Tail Proportioning System usually associated with ABS systems. With a non air brake trailer
either remove air supply line from rear of cab and
plug,install a shutoff valve or use a dummy glad hand. Trailer Air Supply knob will stay in when pushed with line blocked switching from Bob Tail brakes to normal brakes.

dave

Mike M · Jul 30, 2013

While that is a far better set up to use then overloading a pickup I would think you likely have a nightmare with insurance and liscence and CDL needed.

Welding man · Jul 30, 2013

All depends on where you are. My state does not require a CDL or med card for Farm Use and farm Ins is dirt cheap.150 mile radius of farm.Good up to 80,000 GVW.

danofarming · Jul 30, 2013

Yes block off the glad hands and push in the red valve this will give full braking on rear axle. I am sure that a valve could be changed on the rear axle to eliminate the problem.

MARK ROBKE · Jul 30, 2013

I am guessing you have no brakes on the trailer? As others said the bob-tail proportioning valve is the reason for weak rear brakes. Yes plugging off the red air line and releasing the trailer park knob will increase your rear brake application. There are kits to run air over electric. I have seen them,not impressed, but it would be safer than no trailer brakes. Also ,if you are running no air to trailer, you are running your brakes like a straight truck which requires an inversion valve on the truck. It protects you in case of loss of air primary or secondary side. Your truck may have one(tractors are optionally equipped with inversion valves). I can explain it, and how to tell if you have one,but i would be typing for an hour. I would think also if you have no trailer brakes you may be setting yourself up to jackknife blocking the red airline, but you would have more stopping power. Be careful,good luck. Mark

T in NE · Jul 31, 2013

Hook the gladhands together with a quarter between them.
We have a 95 FLD at work that"s bad like that, it applies rear brakes when trailer air is supplied about as much as it should when there is no trailer air. Been told by a truck mechanic that back in the mid-90s the proportioning valves were a little over-acheiving. You can"t hardly stop this FLD bob-tailed without the trailer line pressurized, you may have the same symptom, have even heard of a trucking company who put a few quarters in their cabs for this purpose.

Brakes on Navistar

NEKS

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71INT

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Mike M

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Welding man

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danofarming

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MARK ROBKE

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T in NE

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