My allison is a AT-542 4 speed.
My question is... what RPM should it downshift to 3rd while going up a grade. Right now my RPM's drop to 2100 RPM and lower if I let, and at 40mph or lower and no downshift, so when I manually downshift the RPM's head back up to the higher RPM's where it continues to pull the grade. I start the grade at 2600 RPM's, at 65mph at the bottom of the grade.
Shouldn't the transmission automatically downshift before it reaches that lower speed??

Thanks,
DAYSU