I added it a while back into my tranny. I had one bottle in there for 500miles, then added another bottle and drove another 2000miles (of course I drain the same amount of as the amount of Lucas Transmission Fix I add in). It didn't do anything and didn't improve anything. Just a waste of money IMO.
So I replaced whatever's in my tranny with synthetic ATF and shifting was smoother, even after driving only for 10miles, I noticed the improvement. Its been 13,000 miles of driving since I replaced the fluid.
Lucas Transmission Fix was a waste of money for me.