Jim mentioned that you can check the oil level from the Allison pad. For those of you unfamiliar with this function it's a good idea to perform this after each day of driving.
Depress both arrow buttons with the transmission in N (neutral) at normal idle speed.
Here's some codes for everyone..........
OL,OK - oil level is OK
OL,LO,01 - oil level is low 1 quart - 02 is 2 quarts,etc.
OL,HI,01 - oil level is high 1 quart - 02 would be high 2 quarts, etc.
0X - settling time too short
50 - Engine rpm too low
59 - Engine rpm too high
65- Neutral must be selected
70 - Sump fluid temp too low
79 - Sump fluid temp too high
89 - output shaft rotation
95 - sensor failure

Here's an example of what you might see if you tried this without warming up your trans oil first - OL,70