When i'm going up a hill, or punch the gas there is a very noticable vibration that only last for a second. This only occurs from 55 to around 65mph... when i'm on the interstate doing 80 and need to punch it's smooth as can be. Any ideas, i'm worried this could be major. I'm suspecting a torque converter but i'm not a real mechanic... i just play one on the weekends.

Troy Shafer
00 Lariat Scab

 

How often has the fluid been changed? You may want to do a search for "shudder" to start.