What would cause an auto tranny to whine in first gear?

[BennettDMB13]

Hey all,

A buddy and I just replaced the automatic transmission (4R70W) in my '96 GT. We made sure everything was hooked back up and there was plenty of fluid in the tranny, but when we started it up it has a slight whine at idle. We checked the fluid again and it was still good. We then took it for a test drive around the block and it only whines through first gear....as soon as second hits (and it hits hard ) the whine stops instantly. The guy I bought it from supposedly bulletproofed it. It was rebuilt using Borg Warner friction plates, new steel plates, larger direct clutch pack (8 vs. stock 6 friction disks), replaced roller clutch with mechanical diode, Fairbanks Stage 2 Shift kit, Raybestos Kevlar HD Overdrive band, larger OD Servo. Other than the whine everything seems to work perfectly so far. My question is, could it be one of the components used in the build up or something else?

Thanks a bunch and sorry this was so long

Bennett