hey all i have a 1990tp magna thats been doing strange things. i have found if i turn the o/d button off the car changes gear as normal up to 80kmh ,however if i have the o/d button on the car goes to 40 or 60 normally then seems to go back to neutral,any ideas what prob is or should i just hea:confused: d past the local dealer and get a dignosis done. cheers jayma.

i think your 4th gear is gone mate, dads TN used to do that,

so either just leave it and confine to city driving or change the box most likely,

well ur not supoed to use the o\d under 75klms cos ur wear out the syncro's i think or somthing like that. when was the last time u dumped the old tranny oil and filter and o-ring .
the manual says do it every 30 000klms but most only do it every 100 000 and wonder why it's flaring through the gears or going into limp mode.
these trannys are very picky if the oil is old or low u'll start having problems and if u dont use the right oil it will start to play up as well.
but with that being said its amzing the transformation it makes when u put a service kit through it (internal filter,o-ring and gasket) and fresh oil.

this thread will give u an idea on what the o\d does.
the fisrt thing u should do is service it and see if there are any changes then if it hasn't improve the magna buff , stagma or old fart(amc members) will more than likely help u diagnose (bad spelling) the problem.

also ive got a manual if u need anything scanned
http://www.aussiemagna.com/forums/showthread.php?t=35193&highlight=drive

http://www.aussiemagna.com/forums/showthread.php?t=36750&highlight=tranny

heres a couple of threads about the tranny and o\d button

dont be scared to ask and im sure ull get what u need. also theres a seach button which is usefull and welcome to AMC:D

hey thanks guys for your help.......had car looked at during the week and yep overdrive clutch was gone ...had the transmission serviced had a new kit put in and wow the beast is cruising up to 100kph like a new car.......so hey thanks again!