Hi, I am no stranger to rebuilding transmissions, but this one has me stumped. Rebuilt the trans using suncoast parts, triple disc, and upgraded snap ring on forward drum, problem surfaced about a 1000 miles into it. No codes, but sometimes no forward gears, always have reverse, works most of the time, but happens when trans is warm. My deduction has been a seal that's seeping or sticking boost valve, but seems to me with a sticking boost valve reverse also wouldn't work. When it finally does work, it still has all gears like nothing is wrong Haven't hooked up a trans pressure gauge yet as it works fine when it does. Sorry for the long post, but wanted everyone to get the picture. Thanks.
Have you figured out what the problem was? i have an 01 and i lose all forward gears only after backing up with a trailer attached. i have to coddle the throttle and start out in 1st then work my way through 2nd and into D. been in shop twice but no answers.