Alison 1000 transmission will not shift

[dkamulski]

I have a 2000 Newmar Kountry Star Motorhome with a Cummins 5.9L engine and a Allison 1000 transmission. My transmission will not hold in 1st or 2nd gear. It will not downshift into these gears when I manually shift to 1st or 2nd to slow down. The transmission works perfectly otherwise, during normal driving. I was wondering if the transmission has been programmed to give me this operation and if it could be programmed to hold 1st and 2nd. I would like to put the transmission is 1st and stay below 25 MPH and hold that gear. I would like to put the transmission in 2nd and hold that gear below 50 MPH. I would also like to be able to downshift to 2nd gear at 50 MPH and have the transmission downshift. Currently when I place the transmission is 1st gear it will up shift at about 15 MPH. When I place the transmission in 2ND gear it will upshift at abour 25 MPH.
Thanks, Dave

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[DriVer]

Originally Posted by dkamulski

Currently when I place the transmission is 1st gear it will up shift at about 15 MPH. When I place the transmission in 2ND gear it will upshift at about 25 MPH...Thanks ...

Dave, What you have there is an Automatic electronic transmission. It is not going to allow you to exceed the load and safety limits of the gear box. The TCM will definitely send a command to the transmission to upshift or disregard manual shifts if the safety parameters for input HP & torque vs RPM and load are not within a very narrow operational range.

[Hooligan]

My engine, (Cummins 5.9, ISB 260hp) operates in the range of about 1600 to 2600 rpm. The computer and the transmission (Allison 5 spd) keep the engine within those limits.
When you engage the Exhaust brake at hwy speed, the transmission is told to go to 2nd gear, but it will only downshift when the engine will not overspeed. It goes to 4th gear and holds that until slow enough to go to third without allowing the engine above 2600. As the operator you can't change that protection.
In your case, 1st gear, as rpm increased, light load, the computer would shift early into 2nd and drop the rpm toward 1600. with a heavy load, (steep hill) the upshift would be later closer to 2600rpm, as Driver discussed..

Hope this helps...