Jake Brake help

[BernieD]

There is no change when letting off gas -- no downshift.

Keith

That isn't what I asked. What does the window on your transmission pad say, 4 or 6? What happens if you manually downshif to 4th?

By the way, don't blame your dealer, it's service people aren't qualified to work on your problem. Your brake and engine are both built by Cummins. As I said before, if you have a Cummins Coach Care dealership nearby, go there, if not do you have a Spartan chassis authorized shop handy? Those would be the 2 best choices for fixing the problem.

By the way, cruise control will have no effect on how your engine brake comes on with the power package you have. If you have the cruise on while you are doing 70, if you crest a hill the engine brake should engage while the coach gains speed on the downshill. When your speed drops below 70 the brake will go off and the cruise control will take over again. When you are driving at 70 and you take your foot off the pedal the transmission is supposed to drop to 5th gear if that won't overrev the engine and the compression braking will start. There is a bit of delay before this starts. As the engine slows down it will then downshift to 4th which will bring your speed down quite a bit. The engine brake will continue to slow you down without any further downshifting.

So my first question is; when you take your foot off the pedal what number shows on the transmission pad? That will indicate whether the engine, transmission and engine brake are all communicating with each other.

 

[keithb]

Bernie,
 
        When I have the jake brake switch on and let off the gas, my pad still says 6. If I manually downshift, the numbers on my panel do decrease.

I am taking my rig out this weekend. I am going to take a tester and pull the switch out to see if it is actually doing anything. I am pretty sure at this point that it flat out doesn't work.

If I don't find anything obvious, i will call Cummins next week to look at it -- since I don't want to be STUPID for not just wasting $75.00 in fuel to let them look at it when it could be something I could easily fix.

Thanks,
Keith

 

[JerArdra]

Keithb,

Magboiler is correct regarding 70 MPH.  For example, on our coach if you're going, let's say 70 MPH, I must slightly press the service brake and then when the coach slows to 64-65 MPH I can feel the down shift from 6th to 5th gear and I can see it in my Silverleaf display.  At that point, if I keep the floor pedal pressed the Jake brake downshits another gear every 10 MPH until it's in 2nd gear at 25 MPH and finally it releases (disconnects) at 15 MPH.

JerryF

 

[BernieD]

        When I have the jake brake switch on and let off the gas, my pad still says 6. If I manually downshift, the numbers on my panel do decrease.

Keith

Well that answer says that there is no communication between the engine brake and the transmission.

If I don't find anything obvious, i will call Cummins next week to look at it -- since I don't want to be STUPID for not just wasting $75.00 in fuel to let them look at it when it could be something I could easily fix.

Now you can call Cummins tech support and tell them what is missing, they might be able to trouble shoot the problem over the phone or help you look for the problem. We know you aren't doing anything wrong.

 

[Ron]

The problem could very well as simple as a blown fuse.  Call Cummins as Bernie has suggested.

 

[Gary RV_Wizard]

Allision Transmission are great!!!  I have attended half-a-dozen Allison seminars and one of the things they emphasize is that you can manually press the buttons to downshift  into 1st gear at 65 MPH and the transmission will NOT do it.  They even say if you accidentally manually shifted into reverse at 65 it would not do it.

Jarry,
Not really so astounding, Jerry.  You could do the same thing with the auto tranny in your car. It simply won't do anything to self-destruct.  Automatics have had built in protection for many, many years now.

 

[keithb]

Finally getting back to you about my exhaust brake situation. After I set an appointment to take to Cummins, I decided to call Spartan for a wiring diagram so I could check the basics. The lady at Spartan informed me of a recall for this problem which also causes brake light fuse and several other problems to occur. I checked and sure enough, no brake lights. Spartan overnighted a repair harness and instructions to my dealer and now all is ok.
Thanks to all of you for your help
Keith

 

[Tom]

Glad to hear there was a satisfactory resolution Keith.