I haven't ran my car at the track yet, but am at a point where if I want to upgrade the current 3.23's in the 4th gen rear under it I should do it now.

How much of a drop in e.t. would I see going from 3.23's to 4.10's?

I'll say just use a base of 9.5 et with the 3.23's. (in the 1/8th)

 

Lets see. You've never been to the track to see what 3.23 gears will do. You don't know how much rpm you are at when you cross the finish line so changing the gears can't give you an improvement when there's no real data to base it on.

Now add into the equation that going from 3.23 to 4.10 will increase the torque mutiplication to the rear wheels. Without traction you can easily overpower street tires and offset any gains made with a gear swap.

If you really want to know what it will do then you need to take it to the track and find out.

The butt dyno will feel an improvment in accelleration and your wallet will feel the decrease in fuel mileage.

 

I will not be on street tires. I plan on et streets or simmilar. This is a track only car, so highway rpms and gas milage do not matter at all.

The track here wont open for at least another 2 months, and I'm at the stage in building the car where its most fesible (sp?) to swap the gears.

I'm just looking for a rough estimate on what it dropped others e.t.s

 

Since it's track only, there are plenty of race formulas out on the net to do your calculations.

You want to cross the finish line at or a few hundred rpm before the engine's shift point. This means you need to know where the engine makes it's power and what tire size you intend to use before deciding what gears you need.

On an estimate guess, 4.10 gears shifting at 6800 need a 28" tall tire. If you're shifting a lot lower or only use 26" tall tires then you won't need so much gear.

Do the math and you'll only need to buy parts once.