transmission fluid level

91 GMC Sierra half ton -700 R4 transmission

Can someone explain this to me please. Why is it ,when I check my tranny fluid level two days in a row,it differs quite a lot.(a litre or two) I know it's supposed to be checked when hot, I can drive to the same location (10 miles) then back home and the level is reading higher or lower than before. Why is this happening?? How do you tell when the fluid is too low or high besides reading the dip stick? Will it shift slow or come out of gear??
Thanks

Kevin in Canada

well first is your tranny leaking? also may sound stupid but i had a chevy 1500 that always seemed like the tranny fluid was either lower than normal or higher. so i finally figured out that i need to check it in THE SAME SPOT IN THE DRIVEWAY ALL THE TIME. the slightest slop will give you an inaccurate reading. try it out for a couple weeks.

There is a little tranny leak at the driveshaft seal and that's why I check it periodically. The amount of difference on the dipstick is more than just checking in different parts of my driveway.(1.5 inches) I agree , that can be a big cause of unusual readings. Lately though , it has been reading somewhat consistent. I still can't understand why it can be so different sometimes??

Kevin