Autos will actually benefit more from this, because they had a 3.32 FD before as oppose to 6mt's 3.5 FD. I heard autos see around half a second gain from this. IMO its probably the single best NA mod you can do to make the biggest difference.

 

ISMSolutions over in the reviews section netted a 1 sec gain with this mod for his AT. He has a 12 sec NA 5AT. Now that's impressive!

 

Ok, so if I have the money and want to buy an entire 3.9 unit that I can take to the shop and have them install, how do I get ahold of it? Where can I buy the 3.9 (complete setup)?

So, if I spend the $850 for the 3.9 gearing, it's gonna take forever to install? So, paying more money for the complete pumpkin, it will save me money and time on the install? Am I understanding this correctly?

 

That's correct. You'll likely spend about the same either way (maybe a tad more for a complete pumpkin) but the completely pre-assembled pumpkin will also keep the car from being down for a week or more. You'll also know that everything was shimmed properly instead of having to find a tranny/diff. shop to do all the work. The pre-assembled pumpkin could be slid in by any transmission shop with relatively little room to F things up.

 

ok i think i am seriously about to do this mod and tell everyone my honest scenario, its hard to believe anyone on here cause i think everyone is trying to sell stuff.....


i have an 04 5AT, running 110 mph on 100 shot, my times are mid 12s, and mid 13s NA, i am probably going to just order the gears and get my diff. welded, i dont care about the lsd cause all i do is drag race or light to light, possibly some drifting (the welded diff will help that)

i will let you know soon....

 

Ehhh....you don't want to weld your diff unless this is strictly a drag car for 1/4 mile only. Welding the diff will make your car turn like a 4X4 truck locked in 4WD low. If you're concerned about traction, just get slicks. A 3.9 gear would have you crossing the line at around 5900rpms in 4th. If you got slightly shorter than stock tires (say 25.5" slicks), you could improve you're gearing even further and be crossing the line at around 6100rpms which is pretty dang ideal. With the massive powerband lift from nitrous, the traction of slicks, and all that torque multiplication, I don't see why you couldn't yank 1.7 60 foots and pull low 12s assuming you're going full tilt right off the line.

 

Here's the thread ....

https://g35driver.com/forums/reviews/54259-5at-3-5-final-drive-differential-swap.html