$2000 you've got to be kidding

so ever since i bought my 89' 740 GL my car has felt like it lunges every time it shifts gears. when i bought it i thought nothing of it but it started raining a few days ago and the roads are a bit wet.... so since my car lunges every time (the worst is from 1st to 2nd) so when im stoped at a light or sign awaiting my chance to make a left turn and then proceed to go. the transmission shifts about half way through the turn and when it does it lunges and causes the back tires to slip swinging out my back end as i start to drift around a corner. now drifting is fun (for me at least only when im alone and there is no traffic and on my friends property) but my cars rear end swings out in the worst time possible. During heavy traffic..... So now im pretty fed up with the way the tranny behaves.... i took it to a shop and they wanted $2000 to rebuild it...... (by the way its an Automatic) So this got me wondering. Is this really worth it? i personally prefer manuals to automatics and was looking into putting a M46 or preferably a M47. but i dont know if the bellhousing from the engine to the AW-70(?) will fit to either one of the 2 transmissions. i know it will most likely cost about the same to do the switch but i rather spend $2000 to have more control with my car. thanks for the help

$2000 

foggyjames on here will ship you an m90 for $1000

well lucky me the local pick and pull just right down the road from me has a few 940's or at least i think i remember seeing a few last time that i went in to swipe a mirror... so what would be the advantage then of using a M90? and if i swipe the bell housing off the 940 will it fit to my 740? i know next to nothing about the 940's. so all the help is appreciated. : )

but it looks like ill be hitting up the junk yards soon... the transmission fluid leak is getting worse.... : /