48re acts like neutral in drive
 

so just rebuilt my 48re with all red clutches and kolene bands. installed a transgo shiftkit in the vb and a five star ats tc. installed trans with 1 qt in the converter and 6 qt in the trans(ya i know now this isnt even close to enough).started the truck and put in in "N" then through the gears and the truck would not move.shut down and found proper fluid level spec. poured another 10qt(17 total) of fluid in and started back up. the truck went into gear and drove down the road ok. after 3miles the trans started to slip pulled over and looked under the truck and fluid was pumping out of the front seal.towed back home and now with fluid topped back off the truck will only hold drive or reverse for 5-10 seconds then feels like neutral. when i put the trans back into neutral and then to drive it will repeat the 5-10 seconds then feels like neutral again. line pressure is 80psi in drive and 120psi stall.reverse pressure is 220psi in reverse and 320psi when stalled.govenor pressure is 0psi in drive and 90psi when i unplug the connector. any help would be great.thanks.

Did you use the ATF the clutch manufacturer called for, or did you use ATF+4?

I used atf +4

First off? Why would you run a transmission without the proper fluid level you only had 7 quarts in a 17 quart transmission!?! NEVER EVER START A TRUCK WITHOUT THE PROPER FLUID LEVEL! YOU WILL BURN THE TRANSMISSION UP. Hopefully you didnt run the truck that long with low fluid. If you did you prolly wrecked that transmission. :argh:

Your converter is toasted.