How long to get trans fluid up to temp

[jsoto]

Of course, when one seeks a test drive to seek a problem, the problem does not manifest itself. I did a 10 mile drive though - which I think I need a longer drive. Wanted to be more observant on speed, rpm, when the problem goes away (by applying brakes or load), etc

Anyone know how long it takes to get the trans. fluid to temp ?

New reman trans, tq, etc.
Over the course of maybe 4 longer driving sessions, there's been instances where I feel a pretty heavy shudder/vibration around 50-70 when I coast/let off the throttle. I'm thinking torque converter but my dang 10 mile test drive I just did was smooth sailing.