new gears for automatic?


New Member
Jan 16, 2007
i am going to put new gears in my automatic and i was wondering what gear everyone thought was best as far as all around gear and what gas mileage was after gears. i was thinking 3.73 or 3.55 what should i get?
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26 MPG on the HWY with 4.30's in my 96 TBird. Having had 3.27's( Stock ), 3.55's, 3.73 and 4.30's, in that car, my suggestion is nothing less than 4.10's.
4.10s for sure. I never really noticed a mpg difference when I installed them. I guess my first tank with them did but thats because I went WOT so many times. lol Other thatn the blower this is the biggest difference I could feel.
4.10's, no less in an auto.

4.10's cruising on the frwy in overdrive. 03 GT automatic.



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Omgosh 2,700rpms @ 70mph would make me go insane. However, with an automatic, you need to go with 4.10s. ESPECIALLY if you are going to stay n/a. I love my 3.73s though...but love the blower more. :nice:
I got 3.73's with my Auto just for the fact that I travel interstate every morning to work and going to the lakes on interstate for 45 minutes at 28-3000rpms gets annoying. Granted the 3.73's got me out of the 2200 drone zone so my ears don't ring nearly as bad after longer trips but still taching that high leaves you little room to accelerate much more. IMO the perfect gear for an automatic tranny that still has the stock redline is 3.73's. If your car can handle the higher rpm's then get 4.10's for sure. For me 3.73's were perfect though.
4.10's -- VT Stage II's -- 3600 stall -- 21 mpg on the highway (at 70 mph).

You'll get used to the engine speed at 70. Not to mention the fact that you're making more power in that rpm range, so walking away from traffic is ALOT easier.
That's a huge driver issue. I've heard it can lower times by .5 seconds, although depending on your driving abilities/tranny it could be more or less. Heck, if you can't control your newfound torque you might even get HIGHER times at first just cuz you'll be peeling out through 1st gear :D
I have a 02 GT 5spd and went with 4.10s. My gas milage has stayed the same around 22-24. I have always heard that autos needed a steeper gear, and I wish I would have went with 4.30s. But thats just me. DON'T FEAR THE GEAR! 4.6s love the upper rpm!
4.10's here in both my '03 Mach 1 5-speed and in my wife's '04 V6 automatic. Wouldn't go with anything different, and they are both used as daily drivers and have been on long highway trips without any significant drop in gas mileage compared to the stock gears.