MPV help please
 

Hi, wonder if you can shed some light on my van please? I've just bought a 2001 Japanese import 2ltr petrol auto MPV. Bought it for a good price as the auto transmission is iffy & I'm happy to put the work in to sort it.
The transmission was very juddery when my foot was on the brake in traffic & it won't go into top gear. I've drained the oil once & it was not only over full but black & thick. I've refilled & now it's no longer juddery but still won't go into top gear. So I'm going to put a new strainer (as the Mazda garage tell me it's called) in it, but am prepared that it may still not help.
So if I have to look round for a 2nd hand transmission, is the engine & tranny the same as a 626? Also will it be the 4 speed on that year? Anyone have the part number for it I'm told I'll need that so it can be matched. really appreciate any help you can give.