I must add,,,If you need to get your tranny serviced,,try get someone who works at a tranny shop,,but also works at home,,,you will find the quality of the work is superior and cheaper,( doesn't have the sales manager breathing down his neck) i've seen too many bad things go down with tranny shops,,,usualy because of the service/sales guy,,,,the mechanics are honest,,,but the sales guy will keep you away from them.
A good transmission mechanic can attach a guage to your transmission and he will determine which hydraulic circuit is giving you the problem.
As to "Tow and Go" kits,,,,they are a little harsher on shifting,,but a lot of guy's will swear by them,,for extending the life of the tranny.( lessens slippage )