I recently had a dyno tune done on my 2004 mustang gt to clean up a mail order tune i had done year back.
its cammed, full bolt ons 4.10 gears.
(Note: Car shifts fine butter smooth with Stock, mail order (Brenspeed), and SCT stock can tune)
Tuner said he didnt touch anything in the transmission tab cause they don't do many fords, I should return transmission part to stock or have someone else look at it cause it was slipping bad.
When you are cruising and I hit like 20mph and it downshifts from third to second then quickly up shifts and downshifts again. One time I manually downshifted to second at 40 and it went all the way to first (note lockout is 30 and over)
First thing I did was copy Transmission section from the factory tune over to his tune Fired it up, stick happening, I went through all prior tunes could not get this issue to occur on any other.
I'm attaching few tunes if anyone can solve this mystery ill pay up.
Kaizen stock trans is dyno tune with trans tab copied over.
Kaizen.hpt Dyno tune (with problems)
410 gear ratio only is stock tune /w 4.10s
Bren87firm is mail order tune.