I just installed a 455 in my 67 lark and i kept the same th350 that was attached to the original 350. it was shifting fine with the 350 but it now slips into gear instead of snapping into gear. i was messing around with the fluid level and it was seeming to get better. I was wondering how much fluid really effects slipping. It shifts fine when im cruising but if i punch it, it slips and doesnt snap. I want to hear my wheels chirp second and third, any answers?
If you're low on fluid, you'll definately have slipping, not wanting to go into gear (reverse especially)...very bad juju, you can burn things up pretty fast that way. If your fluid level is fine, then take a look at the vacuum modulator, your 455 may well have more/less vacuum at the same throttle position, which would affect the shift firmness and timing.
Sounds to me like your transmission needs to be rebuilt. It was in good enough condition for the power of the 350, but it can't take the torque of the 455. Things can go down hill pretty fast once things start slipping.
Yes. I went 10.79 with a TH350. Transbrake and all, 1.48 60' times. No problems after it was rebuilt by someone who knew what they were doing.
