When I'm applying the brakes lightly it feels as the retarder is coming on full force. Does anyone know
how it works. I know there is three stages but it feels like it's bypassing the first two stages. It is ruff braking.
Joystick on zero or level one? If its sending the signal for position six it would be ruff braking for sure
Scott
Peter, with retarder turned ON and joy stick in full forward position, light braking results in 30% retard and no braking, harder braking results in 60% retard and some braking, full force results in 100 retard and braking based on pedal pressure same as retarder OFF.
The braking used to work right but now it feels as when I just touch the brake it goes straight
to number six and as winter is coming up I don't want grabby brakes so I need to figure out how
it works so I can fix it.
Have you turned the retarder to OFF?
No I haven't Rudy but when I use my brakes when driving below the retarder activating speed
the brakes work fine.
Perhaps turning the retarder off till you can have it looked at may make braking more normal. I have an Allison guru here in the Houston area. I can call and see if they would help you on th phone Monday. Let me know and provide a call back number if that will help.
When I drive in snow I will definitely do that until I get it fixed. The retarder works the way it is
supposed to. I wonder if is air over electric or just strait air that controls it. If it is air over eclectic
I need to find that air switch as that could be the problem.
Peter,
The system is electric over air. The switch is located on the left side of the coach just behind the start batteries. It is attached to the end of the accumulator tank. This will have one air line and an electric plug that will need to be removed. Depending on how new yours is will depend on if you can take it apart and clean as the newer ones are sealed. Here is a link to what you are looking for.
https://www.foreforums.com/index.php?action=dlattach;topic=38732.0;attach=90399
Here is a link to take one apart
Allison retarder air valve (https://www.foreforums.com/index.php?topic=31477.msg277542#msg277542)
Mike
Thanks Mike I may be able to get at it this afternoon.
Brake pedal/treadle actuates retarder in the 1997 U270 via one air line that has three air pressure switches located on the forward side of the carpeted panel under the dash in front of the accelerator & brake pedal. Panel is held with a few screws buried in the carpeted surface.
Each air pressure switch closes on different low psi levels, like 3, 6, 9 psi, to activate three different levels of retard, similar to the joy-stick which has the added benefit of six levels of retard. Originally Foretravel did not have joy-sticks, so retard only came on with air brakes. There is a wiring harness that plugs into the Allison computer, located behind side carpeted panel in driver area. Joy-stick communicates with computer via a 3-way wiring harness that incorporates the 3 air pressure switches. So likely Allison computer does not know if retard signal is coming from joy-stick or brake pedal movements.
When side dash retard switch is off, nothing activates transmission retard.
A faulty wire or pressure switch could activate retarder levels not expected. Every component has plugged connections.
I found the air pressure switches tied up under the dash on the left side. I took switches out and tested
them and I will replace them as they are all coming on with too low a pressure. They are all on at 4 lbs.
pressure. There is another pressure gauge on the air line before the retarder gauges that I haven't clue
what is for. When I was looking for the retarder gage I found two air pressure switches that are with the
brake light air switches that are normally open the are wired in series that close at different pressures that
I have no idea what they are for.
I checked the air brake drawing and I found out the air switches communicate with the ECM