D40 (Auto)struggling to change gear

[2fttnk]

Hi guys,
So I have a 2010 Nissan Navara D40 YD25 and while driving around MOST of the time it is perfectly fine. However when the car has stopped and I try to accelerate heavy the car is very slow off the line (slower then normal) the first gear change from 1st to 2nd is fine but when trying to change again the revs of the car drop, then go back up then drop again, and this will continue until I release the pedal for a few seconds then try again. At this point it's a 50% chance if it works and changes gear normally or if it dose the same thing. If the car is in natural and I rev it there is no problem. The engine will rev up and hold steady.

No engine light is on,
No errors when scanning,
No idea what is going on, please help

 

[Old.Tony]

When the car won't accelerate, does the engine rev as if you hadn't put it in gear?

I'm wondering if there's a problem with the torque converter slipping too much. There might be something (like varnish/debris) in the valving in the gearbox.

It might be worth taking to an auto transmission specialist (not a small outfit either) and get them to throw their diagnostic tool on it.