Re: Mix and match for 4R70W: Help!

Why not just flush the 93 with some new Mercon V and drive it?
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I assume you plan is to build the truck trans to swap in.
That is not a keen idea. The 04+ trans has no speedo and has a 24 count ring gear vs your pre04 having 6 count for the TOS. Also you will have to use the M8 valve body, the truck VB is not going to work, and it has the wrong TCC solenoid for you computer.

SO, the clean method is for you to simply rebuild the 93 trans you have.
Pull the reverse drum/mech diode from the 04 (FOR SURE!)

The 04+ will have the best planet and sun gears as well, and your 93 gears are probably worn out - notorious for that.

The total solution is to simply install the 04 internals from the direct drum forward(even the pump) into the 93 - save that you use the 93 ring gear/op shaft.
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Get all new electronics for the 93
Get a spiral snapring for the mech diode
use raybestose parts and bands
Jmod if you like (tuner will do the job better)
use the new rubber bonded accumulators and new springs
use the 2.7" od servo from the 04
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yes, a converter is a great idea...talk to some converter builders, no off the shelf crap.

A tune will solve all your shifting and firmness issues probably , and it still drive like a lincoln when you want it.