The story goes something like this: The customer came in to the shop complaining of no overdrive in a 4R70W. There are no codes or obvious external causes, but the complaint is verified on the road test. The unit will not go into overdrive.
A 1994 Dodge R2500 pickup was brought to a transmission shop. The customer complaint was no overdrive when cold and that as the vehicle got up to operating temperature the overdrive would engage but would go in and out with throttle opening.