I have this mustang and it runs and drives great until the top of second gear, then it wont advance into third! is my tranny bad or are there other things I can try

 

best bet to change filter, there's a check ball above the filter spout that falls out or gets stuck and causes all sorts of problems... also try lookin into a new governor that shifts the gears... hope that helps.

 

First, check the TV cable is hooked up and pressure adjusted properly. Does it shift late and hard into second? if so then check cable...

if cable is ok then drop the pan because this will tell you a lot...

look in pan.....if no particles in it larger than grains of salt then this is a good sign...

is fluid discolored and nasty? if so then full service might help...dont forget to drain converter...

when checking governor..check the teflon sealing rings on the gov support tube at the rear...are there groves when rings are located? could be leaking

If you have clutch particles floating around then It is possible the 2-3 shift valve is stuck closed because of this and will not allow 3rd gear.