Posted: Jun 09 2010 at 9:42pm | IP Logged

Brandon, need you to describe this "buck" in a little more detail.  It could be anything at this point.

~A tire thrown a weight, so it vibrates when you hit 55-60
~Transmission low on fluid causing the gears to slip back and forth.
ETC....

Does the engine feel like it surges, gaining power then losing? 
Does it feel like the truck is shaking towards the front, toward the back?

The hmore info we have the better chances we can help you.

BTW, I moved you question into it's own thread to give it more visibility.

Posted: Jul 08 2010 at 12:29pm | IP Logged

i think i have the same problem. my truck "bucks" when i let off the gas; rpm surges, but speed continues to decline without a foot on the accelrator. Then after i get back on the gas, then engine continues to surge (about 1k to 1.5k RPM), then eventually comes back down. It only does this about 5% of the time, but i wonder if its a sign of a larger problem

2008 LE, 60k miles, Automatic Transmission. Silver (if that matters)

i took mine in under warranty; couldnt get the truck to replicate it when the tech rode with me for about 20 minutes. Was scanned for codes, no codes came up. Was told to take it to a Transmission specialist and have them scan the AT for codes, but i havent done that yet.

On another forum i used to be on, my "help" stopped at "take it do a transmission shop"