[Archived]

Per, I am not going beyond where I have because Prevost does not build the Detroit engines and if Detroit sets a 2100 RPM limit that is good enough for me.

For almost 30 years I have enjoyed my Prevost coaches and respected 2100 as a limit. What you or others wish to establish as a limit is OK with me because it is your coach. I just want everyone to understand I do not want your attempts to justify how you use your coach as an approval for other coach owners (especially new owners) to exceed the Detroit limits.

[Tim]

I can’t imagine the stress placed on the transmission, drive shaft and rear end when choosing extreme down shifting to 2nd gear for Jake brake performance even though it’s an acceptable practice by the book, it has to push rpm’s to the limit. It just seems like a harsh procedure to me.

I’ve never seen one come from the factory with a 6 speed Allison programmed for 2nd gear jake, anyone else? I’ve also never heard of one with jake action for 1st gear.

Per, what do you do when on cruise control and needing a little jake action to maintain speed?

[Hisham]

Jon,

While Prevost does not build the engines, they and Allison work in conjunction to program the transmission, and they would not program the transmission the way they did if it was unsafe for the engine, nor would Detroit Diesel allow it. It is not a matter of me justifying anything, it is a matter of getting the facts out to Prevost owners, which apparently you are unwilling to do. I am very disappointed in you, Jon.

[Bernard]

Tom,

I mentioned this last year in our discussion; I did not see a significant difference in downshift harshness when on the road.

I do not know whether Prevost ever programmed the coaches for automatic downshifts to second when on the Jake. It was common on production coaches, like my last coach, which used the same transmission. I know my friend’s coach is programmed to shift to forth. I am not advocating for everyone to reprogram their transmission like mine. I do want everyone to know that if their coach is not programmed for automatic downshifts, that they can safely manually downshift to get the maximum effect out of the Jake.

What I do when I am on cruise and come to a downhill, depends on the grade. If it is a minor downhill, I leave the cruise on, and turn the Jake on low or high as needed. If it is a longer, steeper downhill, I turn the cruise off, and use the Jake as needed. If the Jake won’t hold speed on the hill, I stab brake until I get to a gear that will hold speed on the hill. I constantly manage the cruise and Jake as needed. When I cruise in west Texas, or Arizona, the Jake goes off, unless I get in heavy traffic, then it stays on. I rarely use my service brake. Last month was an exception in heavy traffic on a 6% downhill from Victorville down to San Bernadino. Coach shifted back and forth from second to fourth with the Jake on, and I still needed a lot of service brakes. Without the action from the Jake, and yes, I saw 2,400 Rpm several times, I could have had a real problem with the service brakes.

[Archived]

Per, lets let this discussion end. I cannot ever be convinced your “driving” is an acceptable way to manage a coach, and regardless of who or how you came about with your coach programmed to reach 2nd gear I cannot imagine anything more harsh than a transmission doing its best to get to the programmed 2nd gear when the jake is engaged.

It is abundantly clear you have gone out of your way to find allowing your engine to exceed the PUBLISHED Detroit Diesel engine RPM limits is acceptable and I think that is wrong, ill advised, potentially harmful to the engine, and never necessary.

You can blame Prevost for your situation, or you can use a WARNING as a justification or you can say oral comments from individuals justify your situation and how you drive, but the fact remains I have never ever seen anything in writing by Detroit that says anything other than 2100 RPM is an allowable RPM limit for a Series 60 engine.

But as I said previously, it is your coach to drive and do as you want. Just do not try to convince others without a link to a Detroit Diesel document that the allowable RPM limit on a Series 60 is other than 2100.

[Archived]

Jon,

My programming the transmission to second gear has nothing to do with this discussion. The original question was what is the maximum RPM while using the Jake brake. Prevosts equipped with a DD Series 60 came from the factory programmed to go up to 2,400 RPM while on the Jake brake. I’m just trying to get facts out which apparently you are unwilling to do.

As far as referring to my “driving” in parenthesis, I would have thought such a comment would be beneath you, but I guess I should have known better after you allowed your rich good buddy restort to name calling in the thread last year.

[Craig]

That will now close this thread.