I have a 64 Grand Prix with a 3 speed roto-hydramatic auto transmission. The original 389 2 bbl motor was replaced with a 64 421 tripower HO. The programmed upshift points are 3800-4000 rpms, way below where this motor makes power. Can this trans be be adjusted to allow WOT shifts in the 5000-5200 rpm range? Also, upshifts and downshifts are sloppy - would a shift kit help this problem? I'm told that these transmissions are known to be sloppy shifters and replacing it with a TH 400 might be my best option.
hello;a turbo 400 upgrade is a no brainer. a core is 100.00. much easier than trying to fix an old style tranny.the roto does have an adjustment however it is complicated and imo should be done by some crusty 70 year old trans guy that has never heard of a turbo 350 or 400.