727 pump/input shaft change.

[1994redram]

I rebuilt a '79 model non lockup 727. I put billet servos, red clutches, red bands, CRT manual valvebody, etc into it. I had a new pump here and decided to use it.

Upon starting it, I have reverse but no forward gears. I compared the '79 pump with a '74 pump I have and noticed a BIG difference. Parts places list a 70-77 pump and a 78 and up non lockup pump. The input shaft in the '79 had 3 metal rings where the '74 trans I have has only 2...

Does anyone know if using and early pump on a late input shaft would cause no 1st, 2nd, and 3rd? But have reverse.

Edit: I'm pulling the trans back out and swapping the correct pump back into it. I hoping that is my only issue.

 

[fishy68]

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

 

[1994redram]

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

I did air test it with the old/correct pump that I removed from the trans. It all air tested great. But I last minute decided to swap in a new pump I had.

I ended up pulling the transmission out and swapping the pump out. I put the transmission back in and it works great! The early pump on a late input shaft doesn't work.

 

[oldkimmer]

In 1981 when I was first learning to do trannys the journeyman was doing the tranny in a Ramcharger on warranty. He had the same problem. Tranny was in and out 4 times. They finally replaced the complete tranny. Kim