91 A518 TRANS problem

got a problem with a 91 dodge van with an A518 (350)

any way it takes a moment (a few min or so) for the transmission to engage once in gear after it sits over nite..
Kinda like the trans is empty on fluid..
but the fluid is full

could it be

The TC drain back/front pump?
a clogged filter?
VB problems?

or could it be something else?

If its the TC/drain back or front pump approx what would a shop charge to fix it?

Author: Dakota_Don