That could very well be the problem a the rear clutch feed may be different. Your best bet is to air pressure test things when you get the correct pump. If the lip seal in the rear drum rolled or cut when you installed it that'll cause no forward gears. The rear clutch is responsible for all forward gears. If it doesn't engage you ain't going nowhere. What I do is flip the pump and clamp it in the vice with a rag or soft jaws and stack the clutch packs on it just like it's assembled when in the trans when apply about 30 psi of air to the locations on the pump that feed each clutch pack and make sure it engages good. Don't worry if you have some air leakage. Air will leak far easier than oil so it's common. Just need to know if each clutch pack is engaging good
