Question after 48re rebuild

I have the revmax performance/tow VB. I have no problem with removing the check ball if it is really necessary. Is there really no way to flush the cooler without taking it out? If that is the case how is the rest of the system flushed, more specific the cooler on the lt side of the engine where 1 line goes in before going to the trans. The trans is still out so I want to clean this prior to install.

In all reality, since all the fluid including the trans pan and TQ will be new, could I not add the standard fluid to the TQ for prime, then add a few quarts to the trans through the fill. Then just leave the return line that goes on the trans off which will allow the new fluid to push the old out. Does this seem legit or am I way off?

Thanks for the reply! Everything seem ok so far, the job wasn't too bad as long as you take your time and pay attention where everything goes. You will need a torque wrench and shop press or access to it anyway. With the ATSG manual and the Internet sites it is pretty self explanatory. The most difficult thing was the seals in the kit are not marked in anyway and you have to just match them up to where they go by size but not a huge deal. I am pretty mechanically inclined (fighter jet mechanic) and found this a pretty easy job. For anyone that isn't, it may be a little difficult. I kept thinking something was wrong due to how easy it was coming together. The shifts are completely different from stock but not hard, I would prob prefer a little firmer shifts but it is what it is. Revmax has been nothing but awesome with customer service and tech support every time I contacted them. Any more questions let me know!