SS101

iTrader: (2)

which do you think would be less expensive:

1. buy a 12 bolt with 3.42s and change out those gears for 3.73s when i go to stage 2 of my build up (twin turbos and nitrous for road racing - stage 1 is just a 427 DD)

2. buy the 12 bolt with 3.73s now and have the trans re-geard to compensate (i would have 5th and 6th reduced so that in 1-4 i get all the advantages of having lower rear end gears, but on the highway, the lower 5th and 6th will keep the motor's rpms like or below stock levels so i can get some decent mpg)

thesource

iTrader: (60)

Why do you need more rear end gear with the increase of power ? That makes no sense at all .......

SS101

iTrader: (2)

better accelleration...isn't that the point of any lower gear rear in a performance car???

thesource

iTrader: (60)

The reason to install lower gears is to make up for torque the engine is not making thus letting the car accellerate easier . With more torque , less gear is needed . Check out some turbo drag cars , they usually run a 3.27-3.08 gear in the rear because they make a stupid amount of torque . The lower numerically ratio in the diff is also stronger than say a 4.10 gear is because of the size of the pinion gear . This also applies to transmissions . A transmission with a 2.20 first gear ratio is stronger than the same transmission with a 2.95 first gear ratio but is not much good unless you have the torque to turn it .

thesource

iTrader: (60)

Hope that makes sense to you .........

SS101

iTrader: (2)

it does, but since i plan on building this car for road racing i wont always be in the meat of the torque curve, especially during and exiting turns where accelleration is key. obviously a 427 is going to make tons of torque compared to a 346, but since i have to dump compression to make up for the boost, i'm going to lose some of the low end grunt, especially when the turbos are spooling, again, when exiting a turn.

but you're right to say that 4.10s are overkill, and making as much power as i plan on, they probably wouldn't last too long. in either case, we could go back on forth until xmas and i still wouldn't be any closer to figuring out which option is more fiscally responsible...

thesource

iTrader: (60)

This is why its super important to choose the right turbos for your combo so they spool up quickly . Another thing you have to keep in mind is with the added power , the lower gears will allow the rear end to get loose alot quicker . I personally think you'd be fine with 3.42's and a stock ratio T56 . There is going to be a huge difference between a 346 and a TT 427 !!!!

SS101

iTrader: (2)

you know what...you're probably right. the more i think about it, the less i really need the extra low gearing. besides, i can always drop in lower ones if i need them later on. it might cost more to do that way, but i'll have saved more by then anyhow.

thanx for the advice source...sometimes you just need someone to bounce your ideas off of you know?

thesource

iTrader: (60)

I know exactly what you mean . My brother in law and I both know a crap load about Mustangs but we still bounce ideas off each other before making a decision .