So this is an AOD car and you are lugging it up a hill in Overdrive?
I mean, overdrive in an AOD is like 5th gear in the manual trans cars. It’s not meant to go up a hill. With a manual car you would downshift to 3rd or 4th gear to go up a hill. Same with the AOD. It should really be used for highway cruising at speed, and D should be used when driving in hilly areas and towing and such. Pretty sure it states this in the owners manual.
when my car was an AOD, I drove it only in D, and only shifted into OD on the highway. The OD in these trans is rather weak and can burn out with heat, so use it only when the conditions are proper.
D = 1, 2nd and 3rd gear, where 3rd is 1:1 like 4th gear in a manual.
OD adds an overdriven 4th gear equal to 5th in the 5-spd manual.