What gears for street use?

**Facesmelt** · 06-17-2008, 07:17 PM

I have a stock M6 '99 Firebird Trans AM and I am not sure what gears to get.

I am in need of a new differential anyway and I have only ever used the stock 3.42, but I want to know what difference it will make if I were to get 4.10's or 3.90's?

I use the car on the weekends, mostly for fun. I am looking for the best gears for racing from a roll, and I usually start at a roll of around 40-70 mph. I almost never drop it off the line, unless I meet a friend at a traffic light, but still, all street stuff.

The thing is, the car is stock now but I eventually want to put in a full exhaust including; ORY-Pipes, Headers, and a Good Catback. I am also going get a CAI and get a 224/228 Cam in there, all within the next 6 months.

At first I heard it was really fun having 4.10's on a M6, but I am not going to be stock for soon and I wasn't sure if that was only for the 1/4 mile. So I was looking into 3.90's and I would go lower for 3.73's even, so just give me a suggestion.

Thanks a lot ahead of time!

-Dan

**jbwhite** · 06-19-2008, 06:11 AM

I'm going to be a bit of a contrarian here. If you are looking to jump on it between 40 and 70 MPH, the 4:10s might not be so good, particularly as you near 70. I'm guessing the cam you're going with isn't going to shift your torque peak or max RPM much. If you are out of breath at 6,000, it's going to come on you pretty quick from 70 MPH. You might jump ahead when the hammer is dropped, but it won't take long for a stock gear to catch up...and pass you. I side with those who suggest the 3.73s.

**Jays00ss** · 06-22-2008, 01:43 AM

I have 4.30's in my 9" and absolutely love them 65 MPH = 1700 pm on the highway in 6th. + it really digs out of the hole. Had 3.90's in my old 10 bolt and it was a waste of $ IMO, unless you are pushing some serious HP.

Go at least 4.10's with a 6 speed. If you get an aftermarket rear go with 4.30's. I am glad I did.

Even as a daily driver with all my mods below with the 4.30's, I still am getting 23.5 MPG combined driving.

**LS2Tuner** · 06-24-2008, 10:27 AM

As no one has even asked yet. . . . . . . The most important ? is what size tire are you going to run. It all depends on what dia. tire you plan on running.
That will dictate your rpm range.

**RARON455** · 06-25-2008, 01:28 PM

I had 4.10s in mine and didnt like them, read my post gear swap info for all, in this section I went with 3.73 and love them, I drive my car daily though.

**ksulkosky** · 07-01-2008, 10:16 AM

i hear from a lot of my buddies that 3.73's are better. also i think you might need a new axel housing if you go with 4.10's. not sure...

**LS2Tuner** · 07-01-2008, 11:36 AM

Originally Posted by ksulkosky

i hear from a lot of my buddies that 3.73's are better. also i think you might need a new axel housing if you go with 4.10's. not sure...

No replacement of housing needed for 4.10's someone is talking out the wrong hole. . . . . . . . . . . . . . . . .

**INMY01TA** · 07-01-2008, 02:42 PM

4:10s.

**stoney2677** · 07-01-2008, 03:08 PM

had 4.10's and wish i went with 4.30's.

**ksulkosky** · 07-02-2008, 04:10 AM

Originally Posted by LS2Tuner

No replacement of housing needed for 4.10's someone is talking out the wrong hole. . . . . . . . . . . . . . . . .

yeah, notice I said "i think"

**RacerBob** · 07-02-2008, 04:23 AM

4.10s will wake her up!

**HASTINGSRJ** · 07-02-2008, 04:28 AM

dump the 10 bolt for a 9" or a 12 bolt with 4.11's

**GatorSS** · 07-03-2008, 02:36 AM

Originally Posted by LS2Tuner

As no one has even asked yet. . . . . . . The most important ? is what size tire are you going to run. It all depends on what dia. tire you plan on running.
That will dictate your rpm range.

Bingo. First determine what tires you'll run. Staying stock or going with one of the many aftermarket wheel/tire possibilities out there?

**slpcamaro** · 07-04-2008, 10:26 AM

I run 275's for my tire and I love my 3.73's work good for off the line and freeway and still at around 1800 at 75 mph so perfect for freeway gas milage you wanna keep the rpms at or around 1800 so good all around 4.10's are a little much and if you like me i've taken the car past 155 racing not sure how high that 4.10 will let you go but the 3.73's i was a the end of 5th gear.