Hello, my name’s Ed and I own a 2008 GMC Sierra 1500 2WD, w/o the Manual Mode and Earlier this week, I put my truck in Drive and noticed it wasn’t going over 20(ish) MPH, and as I gave it more gas it didn’t seem to accelerate just made exhaust sounds. I then shut off the truck and gave it about 30 seconds before restarting it, and drove just fine till I had use Reverse. I checked the transmission fluid and noticed it was a bit low, but even after I topped it off I realized it hasn’t fixed the problem. Truck has 179K miles. Any ideas on what may be happening? Thank you.