Pneumatic accelerator pedal

[Cheezewhiz]

So, as title says, I've got a gas pedal that's a pneumatic accessory.

It hisses like a bastard when feathering it down, but clamps off quiet when punching it, or on the rebound.

It works perfectly fine, it's just freaking obnoxious.

Is there a way to quiet it down, or is that just the standard?

 

[cadillackid]

the seal is probably going on it..its normal for it to hiss a bit as you raise up or lower down but n ot hiss constantly or loudly.. pretty common issue though as accelerator pedals end up with a lot of dirt, salt, sand, etc around them.. you can try greasing the seal and the shaft that goes into the actuator and see if the seal will expand and tighten up..



you may be able to look at the setup and get a rebuild kit for it.. I am only familiar with the type that were used on the old detroit 2 strokes.. and there used to be seal kits for those.. they were pretty straightforward to take apart and rebuild.



nowadays there are also electric conversion kits to convert them from air throttle to electric.. no idea how well those work as ive never used one..

 

[s2mikon]

Is it a Williams air throttle? If it is, the throttle system is also tied to the transmission modulator on the 643. Low throttle pressure = low modulator pressure. Also low throttle pressure can also limit full injection pump travel. Kits are available to rebuild both the servo and the pedal. While in there also test your modulator for leaks. It is a non rebuildable air cylinder. Allison used to recommend that it be replaced at transmission filter service. I tee'd a pressure gauge into mine to monitor pedal position when i'm on cruise control. A couple years ago the gauge started reading lower than normal at wot and I went and did an inspection and found a flex line that was beginning to leak back at the transmission modulator.