700r4 shifts out of 1st gear at ~4500rpm, even when shifter is held in 1. Sometimes on the 2-3 shift, I need to let off WOT for a second to let it shift. It has had this problem ever since the rebuild and I cannot figure it out. In a '91 Firebird with ~500hp 383. Any help is welcome, thanks.

Try giving Dana at Pro Built Automatics a call, or, www.700r4l60e.com.
Bill

Install a larger lo/rev boost valve.

looks like i'll be trying the boost valve, will post an update after the swap, thanks.

Link doesnt work. Mide did similar too after a rebuild. I expressed that I wanted the holding of any gear too. They just dont pay attention it seems. Just throwing trannys together and getting the money. And since you have a Hi-Po car, you get the 90 day warranty. **** on that!! I dont abuse my equipment and anyone just looking at my vehicles know how they are cared for. Its just a scam! Im good at alot of technical things, but have never gotten a chance to try my hand in the auto tranny area. I think Im going to do my own from now on. I figure I can f*ck it up myself for alot cheaper. =)

I corrected the link to Pro Built.
I think the phone number is 909.795.1876.
Bill

The 700r4 will overide manual low at high RPM and shift , You can only correct this with a trango 2-3 kit. Some other shift kits may address it to , But you may actually fair better with a govenor kit to raise your WOT auto shift points.