Good morning sir! I have a 2007 Mazda 5 sport auto with 185k miles. I bought it last year and while doing my regular maintenance i changed the tranny fluid. It went about 200 miles before it would only slip in every gear. I had already tossed the old fluid and the lucas didnt work so i got a rebuild kit on ebay and will fix it myself. You said the shops usually mess it up 3/4 of the time so is there anything i should be extra careful for so i dont have to rip it open again.
Spend the money on a remanufactured transmission if you plan on keeping the car and it is in good shape otherwise. Or get a junkyard transmission for a few hundred bucks and gamble on a few if you don't mind doing the work yourself. Rebuilding transmissions is not an "any ol' wrencher can do it" kind of job. You need to check wear on bands, check for slop or restricted movement in planetary gears, valve body, solenoids... When the people in transmission rebuild joints went to school for this stuff and they fail at doing it correctly most of the time, that should be an indicator of the difficulty. You really need a controlled environment (a factory specifically set up for it) to do that kind of work and do it accurately.
