Jake Brake reprogramming

[Fred Brooks]

   I am taking my Coach into WW Williams tomorrow to reprogram my Allison 4000 so when I apply my Jake brake it will shift down to 5th instead of 4th. My question is this, Is the round plug in the fuel filter compartment the correct one they will plug into? If not, please advise. Thanks for your help, Fred

[Mike Shumack]

Fred, our coaches are different years but i believe they are the same regarding the diagnostic plugs. The round plug at the engine compartment (and same for one at dash) is for engine diagnostics.

The Transmission has a rectangular shaped plug, located under the dash. My '05 manual shows this plug located under the removable dash panel next to the engine diagnostic plug, but in fact it was located screwed to the wood framing at the removable floor panel under driver's left side console (i.e. by driver's left knee). I since relocated that plug to the dash location shown in the manual.

[Dave Atherton]

Fred, Mike, the diagnostic plug that is the square rectangle in left of your picture is for older Allison and requires a
Packard diagnostic connector which is very hard to find. Most Allison that I connect into has been setup to use the
j-1708 six pin or the J-1939 9 pin data port connections ( shares wired plug to handle both engine and transmission)
on most all the beavers.  Dave Atherton Retired Cat Mechanic

[Mike Shumack]

Thanks for educating me on this.

[Jerry Pattison]

I have a 1998 Marquis, and have had the transmission re-programmed twice.  The connector for the Allison is in the dashboard, under the removable panel just in front of the steering wheel.  The last time I had it programmed, the tech came to the coach, took a look at the connector and said "oh, you have the old connector."  He went back to his shop and came back with a different cable and re-programmed the transmission.  I have mine stay in whatever gear I am in when I switch on the "jake brake".  So, if I am in 6th gear, it says there.  If I want to go lower, I do it myself.  Works great!!

[David T. Richelderfer]

My experience was about the same as Jerry's.  I took the coach to a Kenworth shop in Pasco, WA and asked to have the engine/transmission reprogrammed to stay in whatever gear it was in when the Jake Brake is actuated.  It used to downshift from 6th to 4th.  When the tech was nearly finished with the job, he received a call from a trucker who was stopped on the road and urgently needed his help.  So he said my job was done and he didn't have time to make a bill.  It was one of those rare times at a shop when the job was FREE!

[Lee Welbanks]

On my 06 PT the com plug is the same as Mike's under the dash section, I also had mine done at KW in Pasco. The tech at first had it shift to 5th, we took it out on the frwy for a test came back and changed it to not shift at all. The charge was $90 if I remember correctly.
My question always was: Why did they set the trans up this way from the start. A couple of old time truck mech's said it was because most of the people that drive these things have no idea what their doing and have no idea what a engine brake is or it's use.

[Fred Brooks]

   Hey Guys,
  Thanks for the guidance and input. It was the rectangle plug under the dash cover. In and out in a half hour. Got on the freeway and was surprised how well 5th slows you down with the jake on "high". I've had a few occasions while driving that you get on a slight downhill grade and not paying attention to your speed and look down and realize your doing 70mph and hit the Jake brake switch. Then realize this is a bad move as the Tach says 2400 rpm. (Dave Atherton would have a cow).
 Glad I have this issue behind me, Thanks again to everyone....Awesome support. Fred