Trans don't engage when cold after engine swap.

[k_eclipse96]

I have a 96 eclipse GST automatic that experienced a crankwalk (walking crankshaft) problem. A mechanic friend replaced the engine with a used 94 eclipse cyclone turbo engine (6-bolt supposedly from Japan surplus). After the installation, the car runs but intermittently dies due to low idling. With some modification to the intake manifold and some vacuum lines, the problem seems to be corrected but another problem emerged. When the engine is cold, the transmission does not engage neither on reverse or drive. I have to warm up the car for about 20-30 minutes before the transmission engages. Consulted my mechanic friend but cannot find why this is happening. Any clue? Appreciate any help.

Only the engine was replaced and everything else are stock. The transmission fluids and filter were also changed at that time.