Help me pick a gear ratio
 

Hi guys I'm getting ready to rebuild a 8.8 diff for my LS2 build. The engine will be making about 400hp and this will be used 80% of the time for cruising and 20% track time. The diff currently has 3.08 gears and since I'll be rebuilding it anyway now would be a good time change the gears if im going to do it. So if it were your car what gears would you use?

Have what sounds like a very similar build... My LS2 and T56 came out of '05 GTO so I have a 0.57:1 ratio in 6th gear. I went with a 3.31:1 (or close to that) in my 8.8 diff to go for what I think is a good balance for cruising rpm's and acceleration. With the 225-45-15's, I think I cruise at 1725 rpm at 60. Having said that, with the torque we have in these lightweight little Mazdas, your right foot's big toe can simply drop and rest against the pedal at a cruising speed and the car just pulls away... It's addictive!

Let us know what you decide to do. Patrick

I have 3.42. There are times I wish 1st was taller but then in parking lots I'd like it to be lower. 6th is used over 60 mph only. With the T56 I don't think I'd go any taller so I chose 3.55 from you choices.

Be sure to select a ratio that will match up to the power range of your camshaft. There is nothing worse than cam surge at highway speeds.

It really depends on what kind of track you are doing with it, what tires, what cam and if you are going to run AC .

I'm on 3.55s with a T56. For autox, depending on tires, 3.73s would be better because you really never get over 4 grand with 3.55s. I run street tires so I can't put much more down anyway but would still like to be more into the power band. But on the big track 3.55s are perfect. 4th gear puts you in the sweet spot that will pull you out of a whole at 70 and run to 125 and often times save a shift.

On the street there are times 3.73s would be better due to the cam. If you have any sort of cam in it that is bucky under 1500 rpm 3.27s or 3.08s will drive you nuts with having to clutch in all the time.

So all around I really like 3.55s and if I was to change to anything it would be 3.73s.

Thanks for the great info guys, I have a mild cam with an operating range of 1600-6000 Rpm and my track time will be at HPDE on big tracks.