I'll soon be purchasing a 5AT coupe and plan to make 3.5 rear-end my first mod. My friend has this on his 5AT Z and that suckker really pulls hard out the hole. An APPARENT improvement over stock. I know when I install these my low end accelleration will increase and my top speed will decrease, but what about my accelleration from speeds of like 85mph - 125mph? Will my accleration at speeds like continue to be a big improvement over stock or ar the gains from a rear end mainly present only at the low end?

 

you will gain acceleration across the whole rev range.

 

Actually your top speed will increase, why? Well as it sits you car doesn't have enough power to hit the top speed that the car is geared for because of wind drag and so forth. By using the more aggressive final drive, you actually will be able to hit a higher top speed because you will be able to overcome more of the wind drag. Now if you do some major HP modifications such as FI, then the 3.3 FD is very useful and your top speed would be much higher than with the 3.5 FD. Theoretical top speed vs actual performance top speed. The 3.5 FD is a great mod for the 5AT and it actually takes some load off the rest of the drivetrain which may improve the life of the tranny.

 

does it affect gas milage at all?

 

This will just give you a "idea" of what you will see..


http://www.350zmotoring.com/forums/s...ht=final+drive

 

Even better


https://my350z.com/forum/showthread....ght=gear+chart

 

Rule of thumb is, the higher the gear ratio, the faster the acceleration, but lower top speed than a lower gear ratio. The lower the gear ratio, the acceleration is not as quick as a higher gear ratio, but the lower gear ratio has a higher top end than a higher gear ratio.

 

How much does a mod like this cost?

 

If you can install yourself, zilch. Find an F/I guy wanting 3.3 gears and swap him his 3.5 for your 3.3 .

 

How many hours of labor would this take?

 

I definitely recommend just swapping the whole rear diff. Its probably only about an hours worth of work. Either trade somebody or find one from a salvage company.

This is THE BEST mod that Ive done by far. It took half a second off my 1/4 ET.