yenkomike

iTrader: (2)

well I have been thinking about changing my rear gears to 3.08 from 3.73 but I thought id see what you guys think. the car is my 70 nova . I will be running a 275 60 rear tire or a 27 / 10.5 et street . here is the setup

stock lq4 ,ls9 gaskets and bolts,
comp 206/212 cam 528/540 lift 114
truck intake
tc-78 turbo
350th 3000 stall
8.5 10 bolt with 3.08 or 3.73 gears.

it is a street car but I want low 10s my thoughts are that the car should have plenty out of the hole and the 3.08 gears might help keep the rpms lower so my smallish turbo wont hurt topend as bad.

thanks in advance.

aknovaman

iTrader: (7)

Keep the 308 gears. With the 373 gears your engine will not have much load on it and a turbo needs load. We did a turbo 85 silverado with 411 gears. The torque multiplication of the lower gears allowed the engine to rev too easily and not make much boost.

Chicago TDP

iTrader: (3)

I put 3.55's in my nova but I have a T56.
Regardless, on the track when you are getting through the traps, you want to be right at your peak RPM and locked 1:1 (NO OVER DRIVE of course)

So, doing the math, you need to know your max RPM where you power drops off.

If you get through the finish line in your final gear at 6500 RPM with a 26" tire and 3.55 gears, you'll be doing 141 MPH (but it will be less with converter slip since I dont think you can lock your converter).

If you went with a 3.08....163 MPH....that gear is WAY too much overkill for your setup.

get a 3.55 gear...my .02 cents

Forcefed86

iTrader: (4)

Hard question to answer.

You may not make enough power to launch with a 3000stall, 3.08, and 27” tire. With that baby cam I’d keep rpm’s low and lean towards the 3.08. What are the specs on the converter? Big torque turbo motors tend to drive through cheapo converters. Also low rpm combos usually require a small efficient converter to couple at low rpm. You could have 20+% slippage on a cheapo 10-12" B&M "performance" converter. I bet power peaks well before 6k on your setup. Youll need an efficient small (aka expensive) converter for your combo IMO.

Might as well get a few baseline runs in with the gears already installed if you haven’t. Depends how much power you make,slippage, and rpm through the traps. Then you have to factor in cruise RPM if it’s a street car and settle on a happy place in between. I’d assume if you run decent boost and don’t weigh 2 tons you’ll run out of gear with the 3.73’s. But a 3.25 may be a better fit than a 3.08.

Better to get hard numbers first IMO. Run it, get some numbers and come back.

yenkomike

iTrader: (2)

thanks for the replies i also have a 3.42 gear i could install. my convertor is a good dual anti balloon plate 3000 it came from a 496 hyd roller nos street car i built. it worked well and i thought it whould be a perfect match for my car. the 496 ran a 331 gear and went 10.30 on 100 shot all below 5800 rpm with very little convertor slip . i have been basing my car around 6200 rpm max. with my little cam and turbo.

Tranz Zam

You'll also want to factor in how much highway time the car will see. Around me, there is a lot of highways so the higher gear (lower numerically) works better for me.

stock48

iTrader: (17)

Need tight converter like a yank Eliminator 3000 and 3.08's with that combo. Turbo will prob pk around 4800-5k. Just keep it between 4 and 5500 rpm and it should still run hard. Plenty of power for mid high 9's if things are right. I went 10.3/130 with one at 4850 lbs.

Forcefed86

iTrader: (4)

Are the eliminators considered a "race" converter? I was looking on their website and I couldn't find the "Eliminator" series.

mufflerguy

Insteresting thread. I was thinking about this also. 5.3 turbo with 650 to the ground. 3000# chevy II and a 200R4 w a 3000 stall converter. I'd like to trap around 6500 which equates to 3.90 (28" tall tire) at 1:1, but my chassis guys is thinking that a ratio around 3.3 would work better.

yenkomike

iTrader: (2)

thanks. i will try the 3.08 gears and go from there . if i can figure out my launch control on my microsquirt 60 foot should be good.

yenkomike

iTrader: (2)

we'll I ended up putting in a set of 3.23 gears. I was going to go with 3.08 but they were still in the axle and my brother had a nice set of 3.23 richmonds so that's what it has. the car is ready to drive and tune minus a wideband .

stock48

iTrader: (17)

It is basically a SC3000 for a TH350~400. I can have him build them custom. The SC3000 is the next step tighter than the PY3400. I have both for my car the 3000 is for sea level, and 3400 for high altitude.

stock48

iTrader: (17)

Good choice I love my 3.23's and I only have a glide. Car still has a ton of off idle NA response. A 3 spd would be even better.

yenkomike

iTrader: (2)

the engine is strong n/a if I torque it up it will break the tires loose around 22-2300 rpm with the 3.73s but im not getting any spool yet. im hoping the 3.23 gears and et streets will let me hold it back more. and a little rear brake adjustment. if not I will get my launch control going and im sure that will do it.

I-H8-RICE

perfect timing too, weather is finally breaking

RonSSNova

iTrader: (3)

I'll be following your progress.
I have 3.73 gears with a spool in my 12 bolt.
I can't go to a 3.42 etc w/o going back to a posi.

yenkomike

iTrader: (2)

im not sure your gears wont be perfect for you . but my 6.0 with a tc78 and a 68 turbine wheel seems to get choked above 6000 rpm from the searching i have found. so im trying to keep it lower in the range. and i ran that 206/212 cam . im just wanting a 10.00 car that drives better than my old 11.00 car with a n/a 406 . or thats what im shooting for anyways. thanks.

stock48

iTrader: (17)

Ron it seems that I saw a 3 series 12 bolt spool somewhere.

yenkomike

iTrader: (2)

jegs sells them in 33 and 35 spline . but im not sure about 30 spline.

RonSSNova

iTrader: (3)

Yep, no 30 spline. Seems odd, I would think it would be easy and in demand. I have good 30 spline axles.

I should call em and say hey, how about some love for the 30 spline guys!