Jake Brakes

[Les Marzec]

I have an '03 Pat Thunder with C12.  There is a three position switch for the Jakes that is suppose to be off in the middle, which it is.  However, it seems that I am getting the same braking in the other two positions.  One is suppose to be full and the other 50%. I don't notice the difference between the two.

Also, the transmission down shifts to 4th gear as programmed.  This makes it tough coming down grades to hold a decent speed.  It actually slows down, and I have to feather the throttle to maintain 50 mph.  Anything much above 50 MPH would have the engine RPM at 2000, which I don't need or like.  Example grade would be the Hallaran grade coming into Vegas.

Has anyone experienced the same issues?  I have talked to some other Beaver owners and have been told that their coaches do not downshift into 4th gear and that they have more control over the vehicle.  I know that this is a programming issue.

Has anyone ever changed the programming?  Just wondering if it is a CAT or Allison adjustment?  I am going to the CAT dealer tomorrow and wanted to be knowledgeable about what others are experiencing.

Thanks

[Gerald Farris]

Les,
Your Jake should have a very noticeable difference between the two different applied states. The low position is two cylinders activated and braking and the high position is all six cylinders are braking. So you can see that there is a large difference in the braking capability between the two switch positions if the system is wired correctly and functioning as designed.

That said, I very seldom use the low position on my Jake.  However, I had Allison reprogram my transmission so that the transmission goes to 5th gear when the Jake is engaged, so that I can go down hill at 70 MPH on slight to medium grades with the Jake on and not over speed the engine, and rarely to never applying any foot braking. If I am on a steeper grade that requires more braking, I just manually downshift the transmission to 4th if necessary to achieve the extra engine braking that is needed.

Most Cat service facilities will not be able to address these concerns, so you will probably need to see an Allison dealer for reprogramming an wiring or switch repairs.

Gerald

[Les Marzec]

Gerald

Thanks for the advice.  

I just talked to my buddy at Allison, and I am going to take it into him either today or Thursday.  Would you suggest the downshift to 5th gear or leave the transmission in 6th gear and manually control the gear selection.  

I like the ability to control the coach more.  Another friend of mine has a '98 Marquis, and he can leave it in sixth with the Jake on, and he likes that.  It seems like a personal feeling.  Your advice is usually spot on and worth following.

Thanks

Les

[Jay and Raylene Todd]

Les,

I recently had mine programmed. Unlike Gerald, I had mine set so that when the Jake comes on, the transmission remains in whatever gear it was in when the Jake came on - ie: all 6 gears are available. There is still braking in 6th gear and as the coach slows, the transmission downshifts for additional braking. If I need something greater, I just manually downshift as Gerald stated.

The reprogramming is a quick change to the Allison computer, takes about 15 minutes, and cost me a whopping $35.00. It would have been free had I been bright enough to have it done at Harrisburg last year, when my neighbor Marty had his done.

[Les Marzec]

Guys

Thanks for all of your input.  I just had them reprogram it.  And they did not charge me anything!  It drives so much nicer now.