FWD Low speed limiter???

[Chev454ss]

I'm picking up a 2009 Yukon XL/SLT today. When I test drove it I put it in FWD low and took off. I could feel the trans shifting, watched the tach rise to upwards of 2k but no real acceleration. I took the sales manager with me for another try at it and it did the same thing. He's telling me that it won't go over 5 mph and nothing's wrong. My BS detector is pegged. I've had other FWD's, a K body Blazer, a 99 Yukon, so I've been around the things before. My son has a 2012 Chev P/U and he raced a Mustang (ya he's a nut) and took him out of the hole up to 30 mph in FWD low, but mine just seems like it's slipping. Your thoughts please?

 

[Chev454ss]

I found the problem! When they changed over to the 6 speed trans they also changed the way FWD works. No more stump puller starts unless you drop the hammer.