There are two tranny pans for the 4R100. One for 2wd and one for 4wd. The difference is the degth of the sump which is deeper for 4wd. That was to help keep the filter intake from coming uncovered in high vehicle angles. The filters are the same except for length of the fluid intake snout. Infact if you get some brand name filters, they will give you a 4wd filter and tell you to cut the snout to a certain length for 2wd.
A 4R100 expert (Brian @ Brian's Truck Shop) once told me that his personal experience showed that stock pans ran cooler than hi-capacity pans. The reason was with less fluid volume, each pint (or quart or gallon, take your pick) of fluid would pass through the cooler more often. As temp's got higher in higher capacity pans, it took longer to cool the fluid off because it took longer to run the higher volume of fluid through the cooler.
