My 60' time is 2.38

 

i pulled a 2.21 60ft on stock general tires with a 3.55 LSD and i was spinning terribly. no transmission mods or anything.

 

As BrotherDave said "sweet spot". Yours has moved since you installed gears. You need to shift at a slightly lower rpm. Experiment, you will re-find that spot when you shift and the vehicle surges ahead as oppossed to waiting too long and getting a little fade. You also need to reduce wheel-spin at launch with LS or wider tires, something. Those 4.30 gears will pop you out of the hole like a rocket when you get it right. Good Luck

 

60 foot before gears and after gears.

 

before 2.7, after 2.38