1966 chevy impala ss / 2 speed powerglide trans. slipping?

Question

1966 chevy impala ss with 327 eng and 2 speed powerglide auto trans. Has recently started slipping after it shifts into drive. I've made sure the fluid level is up, replaced the screen and vacuum modulator. I've attempted to adjust the low band - I can make it stick in low, but cannot improve the slipping after it shifts into drive. Also, after it starts to slip, sometimes if you give it enough gas (floor it) it'll go like hell. Is there anything I can do to remedy this while the tranny is still in the car? I'm not a professional mechanic, but have been rebuilding my various old engines for over 40 years now and would like to avoid a top dollar overhaul. As a side note, I also have a TH 350 that I could put in here. Does anybody know if this would bolt straight in without any modifications? Currently get 15/16 mpg with the powerglide and would hate to lose that mpg. Any ideas??? Thanks in advance...

Answer 1

the turbo 350 will fit with minor modifications biggest concerns will be driveshaft length , front u joint and shifter linkage , you should get the same or better mileage , but your originality will be lost , just get the 'slide rebuilt , nothing sounds as good as a nice running powerslide.

Answer 2

I had same problems with my powerslide.in my 1965 belair 2 dr post I ended up putting in a turbo 350 it went in no problems. just measure from front of case to tailshaft. someturbo 350's had a long tailshaft. which is why its named the 350longshaft. a turbo 400 would be good too depends on how much you wanna spend you could overhaul it completely and take clutch plates and soak them in tranny fluid for at least 1 hr . while they soak take 80grit paper and sand the plate surfaces to rough them up a bit so when they shift they have more surface to grab. ( Our tranny tech is a Long-time dragracer) it worked for mine. tranny never had problems even with my 502 LS-7 motor hooked up to it.