P38 4.0L with a 4.6L autobox problem

Hi!
A friend of mine has got a p38 originally with a 4.0 L but with no engine ore gearbox (he got it with with legal papers for free...that will explane why he did what I am going to explain)
He aswell had a p38 4.6L with no papers (so,not able to make it legal). So he got the engine and autobos out of the 4.6 and got it in to the 4.0.
I went with him today to see how it went because he told me it had a problem with the autobox......when you put it in D the car doesnt move....no matter reved.....but when you put it in 1 it does move (and then you can put it in to 2-3 and D) As long as you dont stop the gearbox goes perfect (it goes up and down gears no problem):But as soon as you come to a stop and you are still in D the car doesnt move again......you have to put it down to 1 again and so on!!
The ECU on the engine is that of the 4.6 (it was changed) And the ecu of the autobox was changed aswell with that one of the 4.6.
I have read that it could be ore the autobox ECU ore sometimes the accelerator sensor that is on the inlet manifold....but dont know!
Has anyone come with this problem and can give me something to look into?
Hope someone can help!
Regards!
Adal

Ideas please!
thanks!

Nobody as come by with something like this?
please..ideas see if it gets better!
thanks!

believe there is a problem witht he box itself, have seen a thread or two on here regarding it

If not email Ashcroft transmissions
Ashcroft Transmissions

Am certain there is a known fault, he is very good re advise or work

The one way sprag clutch has failed, its a rebuild box if you want to fix it.

I know a good place in Hampshire to do it if its any help.