Disco 2 Auto box with no drive

Hi guy's, got a good one for you, 54 plate disco with a 4hp22 box that would only engage drive "either reverse or forward" when the engine revs were raised slightly for 20 seconds or so, then it would drive ok!! I was told the forward/reverse clutches were on there way out, change the box!! Ok got another box, same code numbers etc, took the forward and direct clutch packs out and inspected/measured them great, no indication of wear etc. Fitted the box, drove like a new motor, up/down and all over, about 250 miles later no drive at all! and no "kick" under the brake pedal at start up.There was no noise, no bangs and plenty of oil in the unit, no dash lights!! all selector lights working, by lever and on the dash, (so the xzy switch is working and indicating the correct gear selection), oh and the park holds so the transfer unit is in tact. By the way, took the original box apart, you guest it, no sign of any wear on the clutch plates or with the pump so no clues there then (but, as a positive, i now have a spare box!!!!). I'm now thinking it must be electrical, but how?? Help desperately needed here, any idea's? Cheers.

Hi, if i was you I'd try to replace the transmission ECU(the bay is full with quite cheap units), if you have tester reset addaptive values then... it's possible that the ECU is at fault and even if there's some management problem it doesnt recognise the fault... it's something to be ruled out IMO

Thanks for that sierrafery, that's a good place to start. (mechanical's I understand, electrical's are like the black arts to me !!!!)
Cheers.