Originally Posted by Canteenboy
I am going to give you a bump.
I am also interested in your well thought out, and brilliantly articulated questions. You are indeed a valuable member of this forum, and even a treasure to some. I am honored with your mere presence, Mr. Canteenboy.
I have to reply to this thread after a post like that! thanks for the good laugh
It is normal to feel some "shuddering" from the transmission under hard load conditions. I highly doubt you have done any damage.
Locking up the torque converter can cause more stress onto the clutches inside the trans, but it also allows more direct contact between the engine and the pavement. When towing, most guys like the Torque converter to lock-up later, when the motor can handle jumping to the next gear without "lugging" it too severely.
In the end it is up to your driving style to decide what works best for you. Personally i use Race shifting with 55mph lock-up, and put some ladder bars on my truck. Shifts like a dream, never misses a beat.