ChucksZ06

iTrader: (9)

I lost reverse in my th400 without any syptoms or hint anything was wrong...fluid level seems ok and all forward gears work fine under power. Tranny is a BM unit behind a 502. Any ideas would be appreciated. Chuck

8a8mfh

iTrader: (3)

Might be a broken rear band. Or reverse servo problems, you can inspect the rev servo by removing the pan, servo cover and the servo itself. You might get a check on the band by putting a screw driver in the servo pin hole and making sure the band gets tight when you push, otherwise you need to take the trans apart quite a ways to access it.

8a8mfh

iTrader: (3)

The quickest way to check would be to pull the VB and apply air to the reverse servo feed. A thud and hissing or just hissing is a servo seal problem. A loud bang is a band problem or short servo pin. Might even have a broken servo piston if it's been bottoming out due to a broken band.

ChucksZ06

iTrader: (9)

Thanks for the suggestions.