When I ran Nittos,I found if you burn em to long,youll spin the wheels off the line. Only do a first gear burnout! Mines a 93,,94 started with the tranny comp. Im not sure about the shifting method. But I wouldnt think holding first gear to 5300 is gonna hurt anything! JMO
Here's another idea - your stock tach is probably way off. I've seen these tachs off by as much as 500 RPM at 6000 (my own '90 coupe is 500 too high at 6000). You might think you are shifting at 5500 and are actually shifting at 5000. It will help for you to use a good tach, even if it's just a temporary hookup, and find out what RPM you are really at when your tach says 5500 or 6000.
Secondly, the 1-2 shift should be at the red line, just before fuel cutoff. There is no place in second gear that is better than any place in 1st for acceleration. Your 2-3 shift should be lower, probably in the 5500 range. You should not allow the car to go into overdrive - run it out in D. There is nothing wrong with manually shifting the transmission either.
Do I have a choice how long I hold onto 1st? I just put it in drive, leave at 2K and keep the pedal to the floor. It think I'd be better on street tires sometimes, at least if it spins it spins consistently.
Any chance the car doesn't know when to shift because of the 4.10's? What if its shifting from 2-3 too late? It gets to around 6k which is when I get that sloppy shift. The 1-2 shift is fine because it squeels the tires but that 2-3 feels terrible! Its like its way too smooth. Theres no jolt at all when it shifts.
You really think thats it? I did have a shudder, actually I still do occasionaly. Whats that cost parts/labor? I hate to ask... Will a bad convertor cause these symptoms???
A TC wont help it shift harder,if anything It will shift softer.You need a shift kit.To answer your next question,Trans-go makes a good shift kit.But before you buy one,call them and tell them the gears you have,or you mite get the wrong kit!!,Oh yeah,a torque converter will totally wake up your stang! Its my best mod,better then my 410's