A concrete contractor I know has an '08 crew cab LMM with about 40k miles that has an issue his dealer is telling him is "normal".

With the engine running and moving along at a slow speed (like you would to park) after turning the steering wheel one half of a rotation, the power steering seems to disappear, and it is very hard to turn. This occurs when turning left or right. If the truck is in Park, it is almost impossible to turn the wheel past 1/2 turn.

Dealer has done nothing to improve, says it is normal.

Anyone out there that has had this issue?

I'm not sure of the power steering changes made between '05 and '08?

But, for my '05 changing the power steering fluid really improves its operation -- I think the hydroboost/power steering unit must get hot enough to cause the fluid to break down. Some guys have added power steering coolers.

Here's a link:

http://www.dieselplace.com/forum/showthread.php?t=137081

had a similar problem but it didn't sound as bad. I could steer with the engine running but it was harder than it should be. It ended up being the steering stabilizer. The cylinder hooked to the drag link.

Normal. and any tires other than the oem size makes it worse.

Mine does it bad..Im thinking of PSC rebuild and a ram to fix my promlem...Its crap is getting old..It doesnt help that I have 36x15.50x20 either!

i have same problem..Dealer said it is normal...I say BS but havent found a fix so i live with it

Flushed both '07.5s here and it made a big difference.

make sure to use the gm fluid. I did and it made a big difference. before when i would flush it out with the regular off the shelf stuff. it would make groaning noise when the truck was hot. after I flushed it with the gm stuff problem went away and brake peddle feels better.