ok i have a 91 5.0 mustang engine and stock AOD transmisison. it simply will not shift to third....itll rev and rev slippin like mad and then boom she'll shift just too harsh! its not running right at all. why wont it shift? is it a clutch? or something to do with a so called lock-up? something to do with the fluid pressure...regulator? boost valves, i do not even know what these are. if its a clutch failure, is this normally repairable without removing the transmission? will a valve body overhaul fix this. im lost and need some help from someone who really knows these transmissions good. all replies will be helpfull

thanks
Ryan

 

Mine in my truck was doing that and I had to have the valve body replaced (probably could have cleaned it out myself). There was crap in there somewhere blocking the shift into 3rd until the pressure built up enough to overcome the blockage.....at least that's what they told me. Started out as a slip-sliding shift into 3rd.

JohnF