GMC Repair: Transmission problem maybe?, gmc yukon xl, 2005 gmc yukon xl

Question
I have a 2005 GMC Yukon XL 1500 4 Wheek drive. It has 44000 miles on it and has well maintained. I took it 3 days ago to get an oil change, then a car wash. I then drove it for aprox. 40 miles and then got gas mid-grade. As I was driving the RPM's would go up when I stepped on the gas but the MPH would not go up. As I pulled into a parking lot and tried to go in reverse it would not move at all, it would move slightly in drive but I didn't push it too hard. I put it in N and let it roll back into park. I haven't had any problems until now, the only thing is that it did shut off on me about 2 weeks ago when I was sitting on an incline and I didn't have my foot on the brake and it was still in drive. Can you please give me an idea of what the problem may be. The oil is full and looks good, the transmission fluid is full and looks good. Thank you.

Answer
Hi
If I understand correct, you have NO forward OR reverse?
If this is correct, I would HIGHLY suspect the sun shell of having stripped. It is a fairly common problem on the 4L60E transmission.
It will require the removal and partial rebuild of the transmission.
Parts will be in the $300-500 USD range and labor will be probabally in the 12-15 hour range (depending on labor rate in your area).
It is a VERY labor intensive job, ESPECIALLY on the 4wd.
Now this is just a GUESS...there are MANY other things it could be...pump failed, shift cable, manual shift valve..etc....

IF I have not understood your complaint (forward/reverse), please follow post back.
Thanks
PAwl