95 f250 tranny prob

[brifri7585]

95' f250 4wd. 196k. just bought it a few months ago and never had problems. past couple weeks when it gets warm the transmission isnt shifting properly. shifts fine when cold, after some driving it revs out 1st gear then bangs into 2nd. transmission guy said possible some sensor, he'd call me monday. anyone ever have a similar problem? revs out first etc.... once warm from some driving.. thanks for the help...