mikep2002

iTrader: (10)

Sorry search function not helping me here.

From what I have found in the past the rear gears people are running in turbo cars seem to be stock or not above the 3:42 gearing for the most part. I have read this is for spooling turbo faster.

My question is what are the super-charge cars running? I am considering having my rear done and I wasn`t sure if I should stay with the 3:42 or go to the 3:90. I really wanted the 3:90 I think it would be a nice ride down the highway in 6th gear instead lugging between 5th and 6th with knocking in 6th at about 1300/1400rpm. I am trapping now at 124/125 in the 1/4 with the 3:42 gear. Will the 3:90 hurt my MPH or help my MPH I think it would help my E.T. not sure what it will do with my little F/I setup. Thanks for any info.

SVC707

iTrader: (33)

i went with 3.70's not sure how its going to do yet though but i ordered my rear from scott@driveline and we talked for about half an hour

WAHUSKER

iTrader: (4)

The real answer is it depends on your setup. What size tires are you running? Taller tires mean you might need a deeper gear, like 3.90s. But it also depends on your power level. What rpm are you trapping at? You do NOT want to shift in 4th gear!

I started out with a P-1SC I ran 4.10s (they came with the rear end) & 25.5" tires. But I was topping out before the lights. So I put in 3.40s and was trapping around 5k but lost a tenth. Then I installed some 3.70s and they were perfect.

Now with the D & another 100hp, I may need to go back to the 3.40s. They are just about right now, trapping just under 6k, but when I get the setup perfected it will be faster so I will be topped out again. And I run 27" tires now. Hope that helps....

nvmy2000ss

iTrader: (17)

Not sure on your setup but I would think 3.90's would be a bit deep depending on your cam or what rpm you take it up to. I have a small cam and take it to about 6300 unfortunatly I hit the rev limiter b4 I get down to the end of the track (3.90's). Of course all of this depends on your setup ie tires, rpm, gears, maybe someone can chime in I know there is a formula.
good luck.

mikep2002

iTrader: (10)

[QUOTE=WAHUSKER] What size tires are you running? Taller tires mean you might need a deeper gear, like 3.90s. But it also depends on your power level. What rpm are you trapping at? You do NOT want to shift in 4th gear!


I have BFG drag radials on there 315/40/18. Spinning the BFG`s. with 18LBS of air. My 60` is junk because of traction 2.1 I am pushing 475 at rear tires. It is hard to figure what my real RPM would be at the trap if I was able to pull 1st and 2nd without spinning and had a real clutch. This was the first time I have made full passes with car. Poor stock clutch did not like it I could smell it I am doing a clutch install this winter and I will be pulling motor/rear/trans and torque tube. Figured I should address rear and trans and forged short block over the winter while it was all out. Slicks coming next season. I will not be going back to track this season I was just making some passes before the tear down.

Got Me SOM

iTrader: (2)

3.42 would be good and give still good economy for supercharging i think 3.42 or 3.73 would be the most aggressive I'd go with. on turbos you want something higher (lower numberically to put more load on the engine/turbo spool)

prob isn't your rear gear its that you are a 6 sp, you gotta figure out your suspension. changing your rear gear will make things worse not better until you get your suspension and chassis working right.

ss1

iTrader: (32)

That's a pretty tall rear tire, at almost 28". I'm going with 3.73's in mine, but i'm still running a 275/40-17. 3.90's may be fine for you if you continue to run a tire that tall.

I had some things figured out for you, but then noticed you said the car won't hook up, and the clutch is slipping. It's hard to guess when you can't get a decent run.

Urban Legend

iTrader: (5)

3.42s get my vote.

MyWs62FaST4u

iTrader: (2)

i asked soemwhat the same the question in my thread on GEARS section, so the 3.42 is optimum for a turbo car...

The Red WS.6

iTrader: (4)

I've got the d-1sc AFTER I got my 3.73... I have to damn near hit the rev limiter to see 8psi, then Its time to shift... I don't like it. I tried to go with fuel economy in mind. Then I realized there is no such thing as economy, period, when modding. Too late... anyone want to trade some 3.73 for some 3.42 lol...

SVC707

iTrader: (33)

what pulley combo and what is your motor combo to only see 8psi

Ed @ Late Model Speed

iTrader: (4)

How much boost are you making? The taller gears will help a F/I car UP TO a certain amount of boost(roughly 10PSI) after that, you really need to go to a numerically lower ratio. I know it sounds goofy, but above 10 PSI, I would go back to a 3.15. That will actually slow down the rear tire enough to keep traction.

Feel free to contact me if you want to make your Corvette go really fast, I've been around a couple fast Vette's in the past!

Ed

The Red WS.6

iTrader: (4)

Let me see... the 3.00in pulley the d-1sc came with. Stock block, Stage 2E heads, 224/228, .575 - 113LSA cam, FLP longetube headers (with the cat's still in place), corsa catback exhaust.

mikep2002

iTrader: (10)

I think I want to max out at 9/10 PSI. Now I am rethinking the motor itself maybe I will go with the 402 probably accept the 3.90 gear better???

Sorry I just have a good price on a 3,90 diff. and I would be able to keep my stock 3.42 incase i did not like the 3.90 I have been on the fence as to 347/346 or the 402 was leaning torward the 346/347 but with rear in mind leaning back torward the 402. Can`t make up my mind. Tear down Dec,20