Hey guys I’m stumped and can find no info on this problem, it’s a fresh 4l80e build with current mods dual fed internally hd2 shift kit with parts omitted such as dual fed and pressure relief valve. Rollerized case and clutch hub. Freak show converter, and sonnax overrun clutch kit with a pressure regulating pump valve and accumulator delete. My current issue is the trans has all gears until it warms up then it looses 1st,2nd, and 3rd. Reverse and overdrive still operating as they should when hot. The only thing I can possibly think of at this point would be a leak in my hydraulic system. Has anybody had this same problem??

 

Have you done a pressure test?
That needs to be one of the first diagnostic steps for any transmission issue

 

So I did do a pressure test and the pump isn’t a issue with pressures being put out, I just repair the afl and the tcc valve with no change hoping it would be something simple. And as an update reverse shares the same symptoms with the rest of the gears, I never had it in reverse long enough to notice prior.