Thread: 3.90 or 4.10 gear, please help!

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I have a 406 sbc powered nova currently with 3.31 gears in a 12 bolt posi. It makes power up to 5800 rpm and im launching at 3000 rpm off a 2-step.(4 speed muncie, 2.52 first gear) Im currently running 28'' drag radials but will be borrowing some smaller diameter 26'' Hoosier QTPs to test. On a prepped track, i bogg at the line and hit the traps at only 4400 rpm, meaning i still have 1400rpm to get the most out of the powerband. I know i need more gear as my 60' are in the 2.0 second range. My best time has been 12.60 at 110mph and thats spinnin the tires a bit at launch to make up for the gear, followed by a good hook shortly after. The car screams once it gets goin but my 60' is terrible. My question is this: when changing to a numerically higher gear, will my trap speed increase/decrease or stay the same if the car is still in its powerband at the traps. I plugged in the 3.90 and 4.10 gears into a calculator and the 4.10 seem to put me just under 5700 rpm with the same trap speed. If im going to pick up some mph with the gear swap then the 3.90 seem to give me some extra rpm. I dont wanna go too big and run out of rpm is my concern. Which gear is a better choice or what would you suggest? Thanks in advance.

All your ET is in the first 1/8th mile with most of it lost or gained in the 60' time. As long as you don't need to gear it for the street, just go with the gear calculator numbers and keep the RPM "just under" the torque band going into the lights. By changing to shorter tires as an experiment you should see some change in the correct direction.

4.11 would be a strong choice. It's 39 by 7 tooth count is stronger than the 41 by 10 (4.10) and go further into the season of passes you'll make.
Actual trap speed will be determined by literally making a run, but it will be close to the zone you're looking for.

Thanks guys! Nitro, i cant seem to find a 4.11 gear that Richmond makes for a 12 bolt posi. They only list a 4.10. Its on a 3 series carrier. I guess my question was, do gear changes directly effect trap speed or only 60' ? Thanks

Call Mark Williams Enterprises or go to M2differentials.com along with some internet searching. US Gear has even been producing gear sets designed for the track. Look around for the best deal but not the cheapest.

Richmond hasn't made the 4.11 for years now. That's not a bad thing either because I have customers who have been getting less than 50 passes out of the 4.10 Richmond gears (12 bolt) before the actual teeth went away on them. It seems Ricmond's quality has been slipping.

Look for the "thick" style ring gear for the 3 series carrier.

Deeper gears will improve 60' and E.T. throughout. Then you get to fine tune everything from carb to suspension for consistant runs.

I guess Ive got some shoppin around to do then. I wasn't aware of the structural integrity of the richmond 4.10 Thanks for the heads up Nitro! As for my 60' and E.T. i know this car has mid 11 potential just gotta set the car up just right.

ok, found some 4.11 (thick ring) gears for my 12 bolt. They are made by Yukon Gear. I did a little research and they seems to be praised by many. Does anyone have any experience with Yukon?

i have used them my feeling is. just about any of them are better then richmond grear the last richmond i used was not that nice

Yukon gear sets are good. The Yukon brand gears usually have zero issues with the installation. There have been times that when a customer bought directly from Yukon, they found the gears were another brand and ended up with noise problems.
Just make sure that the gears set in the box is trully the Yukon brand.