If you change from stock gears to 4:10's on an auto will you have to ajust anything with tune

 

Yes. Aithout a tune, your going to find that your car is going to shift very weird. The way the car knows when to shift is determined by three factors:
1. RPM
2. Throttle Position (or load depending on the car)
3. Road Speed.

It reads these three things and references them on a chart. When all three meet the conditions of shifting to the next gear, it will shift. Without adjusting the gear ratio, the speed-o will be off and very commonly under WOT conditions, you will have to let off the throttle to get it go to the next gear. Even part throttle driveability can be a bit odd too, if the gear ratio change is large enough.

 

Yes the tuner can take care of it all. Brenspeed I recommend