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Transmission misbehavin'

Yahoo Message Number: 100363
So there I am, motoring along on cruise control, 60 MPH in sixth gear, economy mode, 1450 RPM. Start up a moderate hill. Speed starts to drop off. Six or seven times out of ten, transmission downshifts to fifth, engine power remains up, speed drops very little.

But...

Three or four times out of ten, the transmission downshifts to fifth, and engine power drops off completely for four or five seconds, then comes back up, speed drops four or five MPH.

If I catch it, I can mash the accelerator to the floor, and I don't loose as much speed. After a few seconds at WOT, the cruise control catches up, and I can get off the accelerator.

Position of the economy mode is irrelevant. No specific degree of incline that I can discern.

Cat C12 and MH4000.

Anybody else have any experiences like that?

Tim Gerrity

'02 Magna 40' dual slide

Re: Transmission misbehavin'

Reply #1 –
Yahoo Message Number: 100371
Tim, my tactic is to watch the boost until it starts approaching max, but before the downshift. I then put my foot to hold the accelerator in position to maintain the same fuel flow (but not mash it), and turn off the cruise. You will hold 6th longer and lose some MPH. You may make it to the top in 6th or drop a gear or two. Generally I can keep it at 45 MPH or higher.

Works well for me. You'll need the cruise off anyway for the decline. All mashing the accelerator accomplishes is consuming more diesel.

Lee (leozbrowski@...) President, CCI

2007 Country Coach Intrigue 12153
CAT C-13

Re: Transmission misbehavin'

Reply #2 –
Yahoo Message Number: 100373
Tim,

Mine  behaves in the same way. I think the likelihood of it happening is  dependent on a combination of the grade incline and speed. I'm learning  to anticipate it, maybe half the time, and try to step on the throttle  enough to keep the RPM constant. Of course on some occasions the  incline is such that it will downshift and the RPM steps up to a new  level where, again, I try to keep the engine from dropping off the  torque curve with my foot.

FWIW,

Dave M. 2002 Affinity #6103 C-12 MH4000
Dave & Cathy M, 2002 Affinity #6103, 2018 GMC Acadia, Linux Mint 19.2

Re: Transmission misbehavin'

Reply #4 –
Yahoo Message Number: 100376
As a Dawg owner I have to chuckle with your Cat problems.  We as dawg owners are always told to keep

our RPM's up for better cooling and performance, but I do agree you have to drive the grades with the

Cruise Control off whether you have a Cat or a Cummins, oops, dawg.  Good luck  and pleasant

journeys!  TWI 2004 intrigue 11731
 

Re: Transmission misbehavin'

Reply #6 –
Yahoo Message Number: 100383
For real I would say the less sophisticated Cat engine is having trouble interfacing with your Allison.  A friend of mine that had a C9 had the same problem with his Allison 3000. along with the 6.0 to 6.3 mpg after 18 months he sold the coach and is now driving an Allegro model with no issues.  I would take your coaches to the Allison people in Cohburg, Oregon and have them check the interfacing.  After all the different troubles I've heard from Cat owners, I think in this case I would check with Allison and since the Coburg Allison shop sold the transmissions to  Western Alpine, Monaco and Country Coach, maybe even Beaver and Safari,  they just might have the answers.  Remember, too, that some of their techs worked for CC at one time.  You could call Dave Remington and Jim Cooley at Oregon Motor Coach Service center, they have a ton of experience servicing Country Coaches.  I'm sure they  will be of help.  Just my thoughts from this dawg owner.  There is also a Caterpillar Club you might contact that has a lot of CC owners as members, and maybe they have an answer.  I had an Issue with my 98 Allure shifting with the 3000 transmission and it turned out to be the cable harness between the the ISC 330 and the Allison 3000.  The harness got charred on the exhaust pipe.  TWI 2004 Intrigue 117311