I have a 94 bonny SSEiand just replaced the tranny as the old one gave up the ghost christmas eve.on the diagnosis with ahand held it popped up the quad drive was failing and now that the new trans is in it still says the same.the dumb question is does anyone know if there is a separate brain box under the hood which controls the tranny?it has the electronic track control and performance shift oreconomy shift buttons.I've tried clearing the computer a few times but the quad drive failure keeps coming up.could someone please help me and let me know.there is what looks to be another electrical box on the leftwheel well,could that be the brain box for the tranny?

https://www.gmforum.com/showthread.p...ht=quad+driver
quad driver can be a bunch of things including the ecm itself or a short in the harness taking out the output, which code are you getting exactly?

the trans is controlled by the computer

Look at the thread Justin linked. It explains it. Considering this popped up after you changed the trans, it couild be the torque converter clutch.