[YourConfused]

Originally Posted by oab_au

I think your problem is related to the line pressure that has been increases when the the valve body was modified.

This raises problems with the Transfer clutch that can bind due to the higher pressure.
It also causes problems with the over-run clutch, because when the box is in D or 3rd position, the over-run clutch is not allowed to operate while the throttle is on or it will cause interlocking.
It knows this because it is looking at the line pressure, that it expects to drop to a set level to show that the throttle is closed.

This is the same pressure that the modification has raised, so it never gets to the set pressure that tells it that the throttle is closed and its OK to apply it.

Harvey.

That sounds like a logical answer. Thanks for the input.