With the torqueflite, which I assume you are using, try starting your burnout in 2nd gear and shift immediately to 3rd gear for the rest of the burnout. I used to burnout in 2nd gear but got a lot better results with shifting to 3rd. I also agree that you need to measure and see if your axle is not square to the frame.
No more automatics at my house. A833 in my Roadrunner Lenco with a soft locker in my Valiant. Maybe try a 4th gear burn out in RR but it has street tires and I am not going to put tires on it. It is my street driver. Valiant is not street legal .
