Jake Brake or Transmission Retarder, or Both

[davidbrady]

I can't say for certain how your bus is setup Chuck, but the owner's manual for the 2002 XLII says:

Press down rocker switch to the first position to actuate system to 2/3 engine brake and press to the second position for a full application of engine brake. Refer to "Other Features" chapter 4.

It seems to imply the first position uses 4 cylinders and the second uses 6.

Attached is a trouble shooting guide from the Jacobs Brake website:

BTW for those of us with retarders, the folks at Prevost Service in Richmond BC told me if the Transynd reaches 300 deg F the fluid is toast and should be changed. As long as the Allison isn't throwing a temperature code, you're okay. Like I said, mine throws a code at 250 deg F. My bus doesn't have an individual dash mounted transmission temperature gauge but there is an electronic gauge in the Message Center Display (MCD, which is the graphical display that reads DDEC info across the CANBus). There's a gauge mode which displays battery voltage, engine oil temperature, and transmission fluid temperature.


The combined automatic retarder action with service brake application is something to be relished. It's like driving a car with a brake servo-booster versus one without. They feel like power brakes.