I have a 1990 Loyale AWD turbo with the 4EAT auto tranny that doesn't shift into 4th gear in "D" on the freeway except on rare occasions when it will hunt between 3rd and 4th gear without warning. Car is at constant speed and I'm not stomping the gas pedal to get a downshift. Any suggestions? Would too much or too little trans fluid have an effect?

Check the fluid level, there shouldnt be too much nor too little. Also, smell the fluid, if it smells burnt, change it. If it doesn't look red, change it. If you can't remeber when you last changed it, change it!

If all that has no effect then it is something more serious , but loosing 4th isn't too bad ; I lost first , then got first back:banana: , but lost the rest :boohoo: , then got a new used tranny and everything is cool now .