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  1. #1

    800 1000rwhp capable diff gear

    Hi all,

    First post here. Sorry if this has been covered before, I have searched and cant really find the information i need.

    A quick run down on my car -

    Its a 92 Mazda RX7 FD with a twin turbo LS3 swap making around 700rwhp at 6psi (wastegate springs). I havent turned the boost controller up (or on!) yet so will be making a fair bit more once the weather gets better and i can do some more road tuning.

    The car has what i believe to be a 92 Dodge Viper rear diff that has a modified casing to fit my car mated to a TR6060

    It has had a bit of a whine after 70mph since i bought the car which was already LS swapped with the Viper Diff, i just made the twin turbo kit.

    I haven't driven it much if at all especially with the turbo kit until the weekend just gone where i was doing a bit of tuning and did the first 2nd-4th gear runs.

    After doing this the diff is now whining at even low speeds and just doesn't sound happy really. I changed the oil after i bought the car and it made no difference to it and its only done about 200miles since then.

    What i am looking for is a rear gear that can hold 800-1000rwhp, it is mainly a street driven car so wont be seeing much drag action.

    I am in the UK so i literally have no one to talk about upgrades, as Vipers are rare as rocking horse shit here!

    Also i am currently at stock 3.07, is it worth going to 3.55 or better off staying with the 3.07 to help with wheel spin etc. I have attached two screen shots with the gear ratios.


    Sorry for the long post!

  2. #2
    VOA Mamba Member
    since 2014
    Central North Florida

    Join Date
    Jul 2014
    A lot depends on what you plan to do with the car, if it's a straight line drag strip only car then maybe a 355 is the better choice but reality is without some form of traction control those narrow tires you have will never grip at those HP levels. Since you say it's mainly for the street I personally would stick with the 307s with maybe a Unitrax LSD. Not sure how it will hold up to the HP and torque but there's a lot of us using the stock stuff vs built diff with higher HP Vipers. Just my 2 cents worth

  3. #3
    Join Date
    Feb 2016
    San Diego
    If you are trying to turn then OS Giken with 3.07/3.55 would be my choice depending on tire diameter. Straight line I would pull it and go solid axle in a 9 inch with all of the upgrades.

    FYI you are not going to break anything you have now with that power level with that width of tire. You have ZERO chance of actually hooking at full load even with a 305 drag slick. There are plenty ofn Gen III/IV vipers running around with something close to that hp and much wider tires without the diff going.
    2010 ACR SSG ~750hp Very Track Focused.



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