mackrl700l76 Posted October 7, 2012 Share Posted October 7, 2012 i have an old eaton anti-lock brake system on my 76 RL700L and it seems to be messing with the brake application pressure.i dont know anything about these systems and am worried it could cause the service brakes to fail during use. i am noticing a hissing sound coming from the "box" on the left fame rail just ahead of the drivers. looks like an old style "brain" for the anti-lock but not sure. if anyone has had this issue please let me know and if so how hard it is to convert to an fmvss 121 air brake system Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted October 7, 2012 Share Posted October 7, 2012 Had the same thing on my 1977 RS700L. I removed it and put in a newer style valve. it always leaked air. Question for you... Does your truck have front brakes? If not how much foot pedal pressure do you need to give to lock the rears. My truck does not like to stop and I have new shoes cams,slacks and hardware... Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 7, 2012 Share Posted October 7, 2012 My RS takes alot of foot pressure to stop. I'm not sure if I could lock the rears. Was told it was the foot valve. Have to wait till winter to put it in. I also have all new brakes and hardware. Quote Link to comment Share on other sites More sharing options...
mackrl700l76 Posted October 7, 2012 Author Share Posted October 7, 2012 same here just did the e-6 treadle valve and a new sr-1 spring brake valve . have front brakes and also new cams , bushings, slacks , drums and upgraded to the 4515 "q" style shoes front and back. i was told to get rid of all the old anti-lock system and go to a standard 121 without anti-lock. i geuss there is a service bulletin somewhere that states the eaton system can fail and youre without service brakes. the sr-1 has two or three pressures too that im told and if you get the wrong one for the e-6 it can create a lot of foot pressure. although im not sure that is the case with mine though. the dealership told me it should be a 55 psi sr-1 but i dont know how they figureed that one out. i looked for a tag on the old one but couldnt find one. Quote Link to comment Share on other sites More sharing options...
mackrl700l76 Posted October 7, 2012 Author Share Posted October 7, 2012 qeustion for lmackattack, does the foot valve have a cluster of what appears to be pressure switches on it ,with wires running to two posts on each one? i have these on mine and just re-installed them with the new e-6 valve. however, i have found that i dont have any brake lights when the spring brakes are released. if i set the spark brake i have brake lights when i apply the pedal and the trolley valve. have brand new seven wire to the rear from the fire wall and L.E.D. lights on the rear. also wierd is that i have brake lights with the trailer diconnected and the park brake released. Quote Link to comment Share on other sites More sharing options...
1958 F.W.D. Posted October 7, 2012 Share Posted October 7, 2012 We had a 1978 Hahn firetruck with what I believe to be the same system- Eaton "skid-trol." Truck had a 671T Leaktroit with an Allison HT740 which stopped pretty good even without a jake. However that electro-mechanical skid control was more trouble than it was worth and in the early 1990's the electronics were disconnected, and the airlines all routed to bypass the box. Quote TWO STROKES ARE FOR GARDEN TOOLS Link to comment Share on other sites More sharing options...
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