Thread: heres a dozy th400

Tweet

ok so got the truck moving under its own power now. weird trany issue that is just confusing. first some back ground. th400 i took it apart and insured all clutches and bands were good. new piston cup seals and other seals. now the issue. 1-2 shift is firm and i believe to be properly timed. 2-3 shift is very late. to make it shift into 3rd i have to let of on the throttle and it will shift into 3rd. and throttle pressure that more than a 1/4 more throttle will make it down shift. now there is a new vacuum modulator in. i am suspecting either a governor or a detent soleniod. now i can not tell if the 1-2 shift is in time due to the fact i am going about 40 km/hr under moderate acceleration it it will shift into 2. i am confused. reverse is strong and does not slip at all. that elimates the direct clutch. help lol

so i checked my pressures and i'm on the high side of all pressures. i am assuming this is due to the low vacuum from the engine at idle but it shouldn't affect while driving. i also think my detent gasket is leaking because i didn't use one. it had a built in o ring but i think it needs the gasket. i was able to lower the pressures by using a vacuum pump on the modulator and pulling 10 inches of vacuum. still confused lol

Clutch clearances AND/OR the total shaft end play are too loose.
Either of the conditions or both of these conditions will cause the later 2-3 shift point.
As long as it feels firm when third hits, you just need to close up the end play/clearances, because you've determined the pressures are fine.
Be prepared to have 1-2 come in a bit earlier than it is shifting now. Easily tuned after you get 2-3 straightened out.