Weird Tranny Problem

Ok driving down the road today and stopped at a gas station, filled up and when I went to leave the tranny seemed to be heasitant to shift. So I carefully drove it home about 30 more miles. The light appeared for the drive train. I checked the fluid and it was low. I added about 3/4 of a quart before it was in opperating range. After that is was working fine. So I hooked up my cheap scanner and erased the code. Everything is normal again and light is off

Weird thing is there is no visible signs of a leak. Should I drop the pan and change filter and add new fluid?

By the way this is on a 2001 Dodge Ram 1500

Whats the capacity of the AP4 fluid?

Thanks in adance.

If the fluid & filter hasn't been changed before, it's now time.
Torque on the filter screws is 35 in./lbs. and the pan bolts is 13 ft./lbs
I'd get 5 qts., put in 3 then check the dipstick. Once it gets up to the dipstick, let it warm up while you put it drive, reverse and neutral back & forth a few times then test ride. Once warmed up, add fluid until the level gets to the middle in the safe zone. Check for leaks.
Don't get a flush job, it's not as good as putting a new clean filter in it.