I am curious if manually shifting into 1st at a reasonable speed & RPM is bad for the tranny?

Any thoughts-

 

Whats reasonable? Under 15mph? I think yes. I have done it in auto cars for years before going down snow/ice covered mountain roads. Why do you ask? Is this for racing purposes? If so its likely not a good idea.

 

Don't do it......Get a manual valvebody kit if you are going to be manually shifting it. you might want to consider a tranny cooler too if your gonna be goin through the gears like that