This article describes a modification that utilizes a seperate foot pedal to actuate the Jake brake, similar to the third pedal that is added in some Monaco coaches.

Many D owners have complained about the location of the switch that actuates the Jacobs extarder.   It is somewhat hard to reach.   Some owners have swapped the location of this switch with the "Jacks Down" light.   This certainly is another alternative.

The seperate foot pedal is a pedal similar to the amplifier control pedal for musical instruments, and is readily available at most music shops and some electronic shops.   Here is a picture of the pedal installed in Dennis Uphill's D.

Here is a picture of the insides of the pedal:

Ideally the pedal would have TWO momentary switches - if it has only one, you will have to add another one.

Here is a schematic, along with installation notes:

Thanks to Dennis Uphill for sharing this info with us