Just ordered some FRPP 3.73 gears from GEF Racing, for those of you that are running 3.73's and are automatic what do you have your shift points set at Everyone says "go 4.10 dont fear the gear" but I am planning on going FI in about 1-2 years so hence my choice.
Before you play with the shift points I think you should do the J-Mod on the tranney first. The J-mod will give you firmer and quicker shifts, making up a little for the quicker acceleration due to the gears.
After you do the gears and J-mod go to the tracks and make a couple of runs and you can get a pretty good idea where to set the shift points at. I have my 1-2 at around 5300 and my 2-3 at 5600. I'm still fiddling with the shift points, but I know that 5800 is too far off for my car.
4.10's are what was recommended for the 4R70W, but I went with 3.73 instead. The J-mod was conceived by a ford engineer that designed the 4r70w and is a safe and inexpensive mod to do to the tranny.
What I did was drill out the holes, but did not change out the springs. Didn't want too hard a shift. Car seems to operate alright and the mod took off a tenth in the quarter mile. Haven't heard anyone complain about the J-mod, but have seen some posts from people that have had problems with commercial shift kits. Irregardless of which route you take you will need to buy tranny fluid so if you compare the cost of a commercial kit and the j-mod, you could save quite a bit of money.
also make sure you get an aftermarket tranny cooler on or your tranny will suffer after the gear swap with more heat being created. One more thing get a high stall converter like a 2800-3200 rpm stall
I bought a Level 2 ring and pinion install kit (pinion and carrier shims, crush sleeve, pinion nut, ring gear bolts and cover gasket, pinion gear and carrier bearings) and 4 oz. of friction modifier.