It is not an inching valve problem. There is always a 2 to 3 second delay before the clutch packs engage. If you drive at mid rpm in one direction and shift into the opposite direction without touching the brake or inching pedal it will still take 2 to 3 seconds to pick up. If it happened only when the truck has been sitting for a while then I would suspect that the pump is bad. We've checked the solenoids and then work fine.
The book says it might be a broken spring in the modulation valve of the control valve.
Any ideas would be appreciated.