Transmission Programming

[HarborBus]

I'm sure this is a stupid question but I am wondering how everyone's transmission is programmed. On our previous plastic coach when the Jake switch was turned on the transmission shifted to 4Th gear (as soon as the RPM would allow it) and continued to shift down as speed decreased. Conversely it would also shift up as you got on the accelerator. The cruise control would not set at all while the Jake switch was on and if it was on while driving the minute the Jake switch was turned on it would take it out of cruise control. I got used to this set up and could navigate the mountainous terrain of the western US without touching the service brakes. The Marathon is set up to allow driving with the cruise control set while the Jake switch is on. Then if I hit the service brakes the Jake engages but doesn't shift down so I have to shift down manually. This may not seem to be a problem but then I have to shift up manually as well and I sometimes forget to shift up. I hope you get the idea.

[garyde]

I have a transmission retarder, I normally brake which kicks out the cruise control. I don't remember however if the retarder will work with the cruise control on. When the retarder is on, it shifts down according to the speed I believe.
My previous Lexa Country Coach, the 3 stage Jake would not work with the cruise control on.

[Jon Wehrenberg]

I cannot speak for later model coaches but our 87 had a Jake which was inop when the cruise was on. To engage the Jake I needed to turn off the cruise.

If needed to improve the efficiency of the Jake I also had to manually downshift. And then when not needed, I had to upshift.

Way back when during the days when Prevost presented seminars at Prouds rallies I remember an exchange between Bill Campbell and one of the Prevost Proud members. He expressed the same concern about having to engage a lower gear manually, upshift, etc. Bill (who was one of the three owners of Prevost at the time) responded by telling the guy that was why they called him a driver. He was actually expected to shift up or shift down or engage the Jake, etc. The comment did not go over real well. The point however is as drivers we do have to be involved and sometimes we actually may have to select another gear or take some other action.

As to my current coach, I leave the retarder switch on so I always have help from the retarder when braking, but if I am on cruise control I can engage the retarder via the steering column stalk and it will engage as necessary when descending hills, so unlike my Jake, the retarder does work when on cruise control and if it engages it will drop a gear.

[flyu2there]

Mine has a two speed Jake, don't know about the cruise interface because I usually am not in the cruise mode when I need the Jake. What I can say, either high or low, it drops the gears in sequence, immediately to 5th and so on. The low setting is sort of lame, kind of like the potato (pac-brake) on my earlier coaches, however the high....like throwing out a big boat anchor. Oh, and did I mention loud......it really makes noise but that's half the fun

John

[JIM CHALOUPKA]

My bus has a retarder.
When driving without the retarder turned on.
With the cruise set there is throttle added and withdrawn as needed to sustain the set MPH.
As an incline is approached and the bus begins to slow down more throttle is applied and the set speed is held.
As a down slope is approached the throttle is decreased and the bus begins to slow down by coasting. This goes on and on mile after mile until more varied terrain is reached where it is necessary to intervene with braking because the down slope is too great and the bus instead of decreasing in speed by coasting under the lack of throttle, actually increases in speed.
Here is where the retarder comes into play.
It has on and off settings with six degrees of retard in the "on" setting.
When driving along the driver can set the desired degree of retard with the lever on the right side of the steering wheel to decelerate the bus on those down slopes where the bus coasts and picks up speed, but which are not severe enough to warrant the use of brakes. (this retard action does not disconnect the cruise control)
Depending on how much the driver wants to be "actively DRIVING" he can continuously move the retard lever to the positions (6) he deems necessary for the situation at hand.
During this process (sequence) the cruise may be engaged and will not be disconnected until it is turned off manually or automatically with the brake. (You may use the retarder in the same way without the cruise, but with your foot on the throttle instead)
That all said the forgoing example is not necessarily the way we like to journey along in the bus, but that level of control is possible and I like it in very heavy traffic in hilly terrain and stop and go rush hour traffic.

[Steve Bennett]

Elliot, you can take your coach to an Allison dealer and have it programed to go to 4th (or any other gear) when you are off throttle with the Jake on. We have had Prevost that were programed this way. I would recommend a dealer that is also a Detroit dealer (most are both) incase they need to change any engine settings to effect the change.

[michaeldterry]

As to my current coach, I leave the retarder switch on so I always have help from the retarder when braking, but if I am on cruise control I can engage the retarder via the steering column stalk and it will engage as necessary when descending hills, so unlike my Jake, the retarder does work when on cruise control and if it engages it will drop a gear.

Evangeline has a two stage Jake, not a retarder, but Jon's comment reminds me of a question I've been meaning to ask, but keep forgetting. I like to drive with the Jake engaged (on) all the time as I like the additional braking assistance - especially in heavy/city traffic. I need to know if there is any reason that I should not leave the Jake switched on all the time. Bueller? Anyone?

[Ray Davis]

I do the same. I have a two-stage jake, and it DOES work with the cruise control. If I start to descend a hill with cruise engaged, the jake brake will come on.

I don't leave cruise on on "big" hills, but going through some of the rolling stuff I passed coming I-10 back from Alabama last week, for much of it, I left the cruise on, and jake too.

Ray

[Steve Bennett]

No problem leaving the Jake on. The only time I shut mine off is if I am climbing a hill with sharp turns where you are on and off the throttle. The Jake will actually keep some heat in the engine when descending a long grade. Which I believe is beneficial in keeping proper piston to wall clearance.

[Jon Wehrenberg]

Unlike the retarder which will heat up the transmission fluid, a Jake is benign. It does nothing to harm the engine and can be left on at all times.

The retarder output is diminished by the computer when it reaches its max of 300 degrees, so it remains within operational limits established by Allison.