Transmission wont go into 3rd

[stevo's pizza]

I am looking to buy a 84 bronco II with a c5 trans. It won't go into 3rd and the owner says a guy told him it was probably a kick down spring that is basically telling the truck to downshift into 2nd all the time. Does this sound possible. Thanks for anyone's help
Steve

 

[ZMan]

moved this to the transmission forum, you'll probably get a better answer here.