red fury

iTrader: (1)

Building a 347ci, 11.1 cr, single on3 78mm setup. Running my stock 10 spokes... 275/40 17" MT drag radials. The car will be 99% street driven with some fun hwy pulls. I was thinking stock 342 gears... what are your thoughts? This is a t56 car

2000WS6TA

iTrader: (5)

i was planning on the same thing but with my 88mm precision. you could probably get away with 3.73s as well with that turbo, my bigger concern is that CR. seems awfully high for a turbo car. are you running meth?

red fury

iTrader: (1)

93 pump with Torco additive... 103 octane mix.

Super Slow SS

iTrader: (9)

I have the exact same setup and just moved back to 3.42 from 3.73 gears ... for mostly street driving I love it, a little harder on my clutch though, and with your compression it will be a little harder on the engine also 3rd gear +. I had no problem hooking 275 MT Street's with either gear. If you already have 3.73 its probably not worth the switch, I did because mine were making a terrible whine. If you are building a new rear I would go as close to 3.50 as possible with a 6-speed car, its been debated 100's of times and that is the consensus.

red fury

iTrader: (1)

Besides the 3.42 I was playing with the idea of 3.23s.... This is a weekend warrior, hwy car.

The BallSS

iTrader: (9)

Not 4:10's. I have them and I shift every 2 seconds lol. I've also pondered the 3:73's but am open to everyone's input.

stevieturbo

Really depends on speed range, but 3.42 is a good number

red fury

iTrader: (1)

Yeah, the 3.42 gives me more than enough mph to play with... 156 at 7k in 4th gear

coltboostin

Stick with what you got. M6-850+whp and the same tire you have-and I lay waste to it anything above 700whp with a 4.10 rear. I'd kill for a 3.27!

red fury

iTrader: (1)

Currently I have 4.10s... I really need to put a steeper gear in thats why I am playing with the idea of 3.23s or 3.42s.

stevieturbo

I've had 3.27 and 3.55 in my car, 37-3800lbs both supercharged and now twin turbo.

Usually tyres around 25.3" diameter, ie 235/45/17 or similar.

TBH the 3.55 is the nicer to have, it just leaves 4th and 5th gear lacking for racing and top speed. Regardless of what any calculators say that combo will not achieve a genuine 150mph in 4th gear at 7k.
Even with a 26" tyre, ie 255/50x16 when racing it will just barely scrape 150mph at 7k.

I now run the 3.27 as it just gives me more headroom in 4th for 150+ and 200+ in 5th. The 3.55 just dont do that for me.
If I didnt need to hit 200mph I'd probably go back to the 3.55

Redbull87

iTrader: (3)

I will say ive wondered about changing gears also and unlike you guys with stock 10 blot rears..i have the more rare 9bolt from the 80's lol.It has 3.27 gear.Mind you i cant launch hard on it for fear of shattering everything in it but it leaves smoothly pedalling the car to death before matting 3rd gear.3rd is my money gear..it winds out and to top out 4th is beyond jail time.I do more hwy than anything else and it is great for top speed.When it breaks..and I get a new rearend..Id be going with 3.42 or close to there for better track times.For now..its a hwy dream crusher keeping me in boost.

coltboostin

Easy solution, make more power.

red fury

iTrader: (1)

RedB... how are you liking the performance of the on3 78mm, spool ect? I imagine for the cost, it is hard not to enjoy it.

red fury

iTrader: (1)

Thanks for the input from yalls personal experience! I am going to try out some 3.42s

red fury

iTrader: (1)

StevieTurbo your car is getting it done! Taking a 4door and making it work like that is impressive to say the least.

stevieturbo

Wouldnt matter if you had 1000 or 2000hp...if you're rpm limited you're rpm limited, and I dont really need to be spinning it to 8k or beyond just to run a shorter diff.

gnx7

iTrader: (28)

love the 3.31 gears in my 8.8" out back.
For my car without boost by gear the power would be useless.
275/50/15 puts the power down much better than a 275/40/17 both were drag radials.

I'm pretty sure you can swap in a Mustang 8.8" into an Fbody with GM bolt pattern on the axles. Can't remember who makes that.

stevieturbo

There are many threads in the axle section where people sway the 8.8, some do all sorts of fabrication to allow it from as simple as swapping axle tubes to using the full 8.8 axle.

It'd be nice if someone made a pumpkin to suit the 8.8 diff, but let you bolt it into say a 9" style housing, would make for easy diff swaps in a more efficient diff design.

GR33N PHOEN1X

For sure stay at stock gears. Yes a lower ratio would be more fun but for street driving, you don't want yo take that hit for mpg. Besides, high cr and turbo set up, you'll have a hard enough time keeping traction.
Also- have you seen the reviews for on3? I'd be careful with that turbo