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which gears!!?4:10/3:90

This is a discussion on which gears!!?4:10/3:90 within the Drivetrain forums, part of the LSx Technical Help Section category; Looking to gear swap my 6speed car,it has an ms4 cam in it and the 342s are not cutting it ...

  1. #1
    Member RedHot99T/A's Avatar
    Join Date
    Jul 2010

    1999 Trans Am ws.6

    which gears!!?4:10/3:90

    Looking to gear swap my 6speed car,it has an ms4 cam in it and the 342s are not cutting it anymore getting sick of it falling on its face under 3k and having to play catch up.I do drive the car a good amount on the freeway and was wondering if the 4:11s would kill that for me...just want some opinions from you guys/gals.I was told that the 4:10s are smaller of a gear and are more prone to breaking,and the 3:90s are a nice middle between 373 and 410 gears.what do you all thing i should go with? and i know the 10bolt is a waste to put money into,BUT looking at a better rear is outta the question right now.Also what brand gear/instal kit would you suggest too? thanks

  2. #2
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    East of Cleveland, Ohio

    99 WS.6 - Modified

    4.10's are a great gear with the six speed. That's what I my 9". That said, the 10 bolt won't like them. Especially if you get traction. Expect problems, the most fortunate being busted gear teeth - ask me how I know. No matter how tough you try to build the rear, it's not really meant for that much power to be put through it. I built mine as tough as you could make one, and ended up snapping teeth off three sets of gears - one being 3.42s and the other two being 4.10s.That's when I ordered the 9". If you're going to change gears, go 4.10. But I really wouldn't recommend doing it in the 10 bolt.

  3. #3
    Junior Member nathanWS6's Avatar
    Join Date
    Jan 2012
    spring hill,FL

    2000 trans am ws6

    from what i was told the 3.90 is alot stronger of a gear cause it's the only one still made in Italy not china and mexico like the 3.73 and 4.10..
    if you lay them side by side you'd see the difference in construction

  4. #4
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    You could contact U.S. Gear to see if they make the 4.10's for the 7.5 rears. They are American made gear sets and are the best there is.

    Frankly though, you aren't going to gain any strength going to 3.90 vs 4.10, because you still only have about 1.5 teeth contact patch at any given time, which is why they are prone to sheering the teeth off. The 7.5" ring gear diameter just isn't that large no matter how you slice it, and when you start putting the small diameter pinions in with numerically higher ratios, the tooth contact patch shrinks. Even a 3.73 gear only contacts 2 teeth at any given time. You can beef everything else all you want,,,you'll still have minimal tooth contact patch with numerically high ratios and that's going to be the weak point.

    Your best bet is to go with a stronger rear (larger ring gear diameter).

  5. #5
    Member Supershafts's Avatar
    Join Date
    Apr 2010
    Long Island, N.Y.
    1971, 73,78, 85,92,95,

    The motive perf gears are made in italy, there are other gear companies that aren't using china though, precision gear is US made as is US gear, people choose to use the lesser

  6. #6
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Ugy Lower Corner of AL

    Navy Blue Metallic
    98 T/A w/a little mods...

    Yukon Gears are some of the best, then again they are oriented for rock climbers (most of their business). I figure if they can handle the monster torque of rock climbing they can handle anything on the street/strip.

  7. #7
    Former Mopar Man 2002ssslp's Avatar
    Join Date
    Jun 2011
    Branchville, NJ

    Silver & Blue
    02 Camaro SS, 04 GTO

    3.73's in a 10 bolt. No lower.
    My ride is a 2002 Camaro SS SLP #3296 with 30k, LTH, 3" Y, CME, Frost tune, K&N, ported TB, Blackwing lid, Bellows, MSD, Denso Iridium, and 85mm MAF, Bilsteins, Eibach springs, SLP strut brace, Adj. Panhard, TA Girdle, UMI, Pro 5.0, Nitto NT555
    My wife has a 2004 GTO with the rare SAP, 18" wheels, K&N Cold Air System, MSD, Ported TB, Frost tune, Denso Iridium, Flowmaster cat-back, 3200 Yank, 75k

  8. #8
    Join Date
    Mar 2006
    West Virginia

    Y2K WS6

    I have a slightly bigger cam in my vette 239/247 .624/.624 on a 114 lsa I did 4:-1's and love it.... Ditch the 10 bolt for sure ... I cruise at 80 most of the time and no problems

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