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Boosted GT-2014, which diff gears(3.31,3.7,3.9,4.1)is the best for course?

Hello team,
Good day.
My car is Supercharged with D1SC unit making ~650 RWHP - Aluminator Engine 9.5 Compression, along with:
- Full Koni suspension kit (Orange kit)
- Swaybars and lowering kits.
- Squared 19x275 Federals
- Manual Gear MT-82 (upgraded with Stage02)
- Factory Differential 3.31

My questions are:
1- For the differential, I saw those differential upgrades:


So, which one is the best, and why?

2- About the gears, which rear-gear is the best for my mods (3.31 the default one, 3.71, 3.9, 4.1)
Considering that my car hit the course-track 70% and sometimes hits Drag as well.

3- If I purchased either of any Torsen diffs above, is it comes by default with 3.7 gears, or should i get it separately
Exp. Type
Exp. Level
5-10 Years
Philly Metro Area
If you've already driven on your normal tracks with a a track app then you should analyze when you need to upshift & downshift and what your RPM limits are. If you have to shift too many times this may mean you have too high of a numerical gear ratio and should consider a lower numerical gear. Same thing if you are hitting your redline at the end of a straight.

With your 3.31 gears, if you need to downshift into 2nd very often, then perhaps going to 3.55 may be beneficial.

You should have a video of your laps with a data overlay using your 3.31 gears and then using a gear/rpm calculator, figure what RPM you would be at with different gear ratios during various turns and straights.

I wouldn't even consider anything higher numerically than 3.73. And with only 275 tires and all your torque, you'll probably have traction problems when you're powering out of a turn. Definitely traction problems at the dragstrip with 275s.

The fact that you also take your car to the dragstrip would lead me to recommend the second Torsen (M-4204-MB). However, to save money I would recommend you order P/N CR3Z-4206-A. You'll save about $300. This Torsen is the strongest of the T2 or T2B differentials.

To my knowledge, none of these differentials come with 3.73 as a "default". While the Boss 302 came with 3.73, the 2013-14 GT500 had the same differential with 3.31 gears.
Last edited:

Grant 302

basic and well known psychic
What's your trap speed and RPM? What tire are you using for drag racing?

What are the various top speeds at the different road courses?

And dang, it looks like the pricing on Torsens has jumped a bit lately. The Boss unit was in the $800-850 range for several years, IIRC.


Tramps like us, Baby we were born to run...
Exp. Type
Exp. Level
3-5 Years
Brighton, Colorado

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