Jake Brake

[davidbrady]

Hi Chuck,

The retarder has a six position steering column stalk and a dash mounted on/off switch.

Dash switch on:
stalk in position zero: retarder braking assist with brake pedal application, no assist with accelerator lift,
stalk in positions one thru 5: retarder assist with brake pedal and assist with accelerator lift.

Dash switch off:
no retarder assist.

The thing with the retarder is you have to get used to higher transmission temperatures. I built up a mental block over the years of BB ownership of where I thought the transmission temps should be. I needed to get past that block. It takes some confidence in the systems to let your transmission hit 250 deg F. Once I realized the limits imposed by Allison and Transynd on temperatures I became more comfortable running higher temps.

I agree with you about losing momentum as the jake engages with every accelerator lift. That's gotta hurt mileage. I also don't like the load reversals on the driveshaft and running gear that accompany cyclical retarder engagement, jake or transmission. The transmission retarder will minimize these reversals with the stalk in position zero, allowing them to occur only with brake pedal application. This is why many folks run with the dash switch enabled all the time. I don't, mostly because I'm not a big fan of load reversals on the drive train, even if only with brake pedal application.

Some Prevosts are equipped with both the transmission retarder and jake brake. I noticed recently while reading the manuals that Prevost warns against using both at the same time because of excessive driveline torque.

I also read in the Allison manual that the transmission retarder is very dependent upon proper fluid level. Too much or too little fluid can both lead to excessive temperatures. The level needs to be correct. My mechanics over at Burke Christian Tours change the fluid in their buses every 25000 miles. They just changed mine. I believe the charge was around $450.00. Burke's has transmissions in service with well over 500,000 miles.

On a side note, Burke's just bought 10 new buses. They hate the Volvo engines. The oldest bus in their fleet is 1996 and they're going strong. I don't know the mileage on the '96's but I'll ask next time I see them. I'm sure they're well over a million.