Allison Transmission question

[Jerry Pattison]

My transmission (1998 Marquis Diamante, C-12 Cat) suddenly began pausing during up-shifting.  Sometimes it seems that the transmission starts to shift, then thinks about it, stays between gears maybe 2-3 seconds, then goes into gear, sometimes "with authority".  I am using Trans Syn.   Interestingly, I had just changed chassis batteries.  Any ideas?  Down-shift seems OK.

[Edward Buker]

Jerry,

If you pull all power from the system, like when changing chassis batteries, the ECUs go through some learning phase. You may find this all disappears fairly quickly if that is the cause. In addition the system is designed to drop engine power during the upshift especially under load until the shift is complete. I know you are sensing something new and have probably owned the coach for awhile so this could also be a real transmission issue but give it just a little time to see if things go back to normal. A fluid level check is also in order.

Later Ed

[Jerry Pattison]

Thanks, Ed!  Fluid level is OK.  I'll just wait for the "learning" period to end!

[Edward Buker]

Jerry,

If you have a Silverleaf or Alladin that has either torque or HP as one of the parameters that you can monitor, if you go to that display and maintain a steady somewhat aggressive acceleration pedal position you will see the HP or Torque rise with RPM and then decline during the shifts as the engine and transmission ECUs work together. Once shifted the HP/torque rises and acceleration continues. That is all normal if that is what you are sensing.

Later Ed