Other than what TomC posted…..is your Allison transmission’s oil temp normal? Higher temp than normal is possible that transmission system not in good working order:
1) Smell & color of transmission oil.
2) Torque converter lock-up is slipping or not on.
3) Multi-disc clutches is slipping.
4) Torque converter is damaging internally.
5) Transmission’s pressure circuit is low.
6) Retarder is dragging
To all bus nut…..If you don’t already have two transmission temp gauge in driver compartment…than for your peace of mind (if you want to) is to install them properly.
1) Thermocouple (welded tip for quicker respond) tap in converter’s outlet line where it begin…..the one that go to cooler.
2) Thermocouple tap in transmission’s oil sump pan.
PS…your electronic DDEC may already connected to perform the above.
When you are in lock-out while accelerating….the converter’s out temperature will go 40°F higher quickly and the longer you continue to heavy accelerate….the higher still…..bottom line is to never go higher than 300°F for longer fluid life. It like having a performance indicator in regard to converter. However while in lock-up, there will be no rapid change of increase temperature.
Pan’s temperature should be around 260°F or less but never over 300°F while heavy climbing or you will shorten transmission’s oil & transmission’s life.
You don’t have to have them but it a peace of mind at your disposal.
Otherwise lost of power….your increase (depend how much) pay load is your reason if all (other than trans) else is OK. Or it just getting use to it after many driving miles…thinking it not the same performance as before.
Sojourn for Christ, Jerry