Engine-Trans question

[JohnDolyn]

Has anyone experienced a case of the Allison 2500 transmission not downshifting when the keypad indicates that it should shift to 4th? Any recommendations as to how to trouble shoot this would be appreciated.

Thank you
Ray

[DriVer]

Quote:

Originally Posted by JohnDolyn Has anyone experienced a case of the Allison 2500 transmission not downshifting when the keypad indicates that it should shift to 4th? Any recommendations as to how to trouble shoot this would be appreciated.

Ray, i wish I could help you but the guys at the Allison shops are pretty good at this stuff.

I expect that the machine will eventually downshift to 4th on its own when it needs to or from a standing start. 4th is usually a gear that is readily accessible unless the engine is in high revs.

[MaverickBBD]

Ray, not all that familiar with the 2500 but on my 3000 when the engine brake is engaged the key pad goes to 2 because that is what it is eventually attempting to get to. I like to watch the computer as it indicates what gear I am 'requesting' (in this case 2) and what gear I am actually in (6,5,4 or 3) on the way to 2. It reminds me of Jack Nicholson in "A Few Good Men"; 'You want second gear? You can't handle second gear.' These things are pretty smart. I attended a seminar with an Allison tec and he said you can be driving down the road and press reverse and nothing will happen until the transmission say it's okay to go to that gear. I've never tried it. I'll take his word.

[Vegasdan]

If the downshift will mean too high of RPMs then the Allison will not do it.