replace the valve body on that 4r100 with one from John Wood automotive or BTS transmissions. Wood is in Ca & Brian's is in Ar. Both guys build killer trans % valve bodies. Tell them how you want it to shift and they will tune it accordingly. Love my JW. They can give you quick but not harsh shifts which will reduce temps, lengthen clutch life. Will pay for it's self in extending the life of the trans. If you ever do need a rebuild DO NOT let them mess with the vb. Keep the one you bought. Much better & safer than a cheep shift kit. Might have the trans flushed and see if that helps. Is the overdrive light flashing? could also be a selenoid issue.
Glen
04 Tail gator XT 34' 5th wheel garage model
200w solar 2 GC2's 800w inv
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99 F350 CC DRW 7.3 ais intake, adrenaline hpop, JW valve body,
cooling mist water inj, DP tunes, 4" exh sys
trucool trans cooler added
2011 RZR 900xp