gearing for 8xl in maxx ?

[speedy]

if i can hear the motor riving high like all the time and the slipper is tight and the rest of the drive line i fine does that meen that the motor is undergeared ? i use maxamps old 8000mah packs (two 2s8000mah in series ! )
and with the feigao 8xl motor that i use now i got only aboud 20mins runtime is that normal ? i have the new e-maxx and stock tires. even with 22/68 gearing the motor rives high, but i guess that coud because of the lack of traction on the snow. Woud it make a big difference if i get som trakpower 4800mah pack ? they are 200g+ lighter and has a way higer dischargerate....