When things will work... but are slow starting to do it is one of the most common things for Trans-x to fix.... those changes are causes by hydraulic pistons and thus are directly related to pressure and FLOW of fluid... if varnish is stopping up a control valve hole then the things work slower than they should... in the worst case it slows the actuation of the clamping ability on the clutches... and allows slipping and excess wear fast... like riding the clutch....
Be sure to find out how much fluid your trans uses...and read the instructions on the Trans-x... it may take two cans to properly dissolve the stuff... my wagon did..... If you do a search you will see lots of my instructions on this ....