I really need help with this, ideas, suggestions, just share thoughts or whatever......the questions: Has anymone ever converted a 1985 Buick regal from a 3 speed automatic tranny to a 3 speed with overdrive automatic tranny? If so what does it entail? Thanks

Sorry, I don't understand your question. If you want three speeds WITH overdrive, you just need to change the axle ratio (not technically overdrive, but has similar result). If you want three speeds PLUS overdrive you need a four speed. Some Chrysler 3 speed (Torqueflight) automatics have an add-on to give four gears for overdrive, but I don't think GM ever did that.


Years back, transmission substitutions were fairly easy mechanical drop-ins, but now, most technicians are reluctant to change to anything that was not a factory option for the particular vehicle and year. This is because it may not interface with the remaining parts of the car, particularly the electronics.


I doubt if there is enough interest in that type of switch for anybody knowledgeable enough to do it to bother. Sorry to rain on your parade, but if you need a new transmission, you probably should get one like the original; if you want 4 gears, you should trade for a car that has them.