Qkslvrc5z

Doing a blower and blower cam on my car soon. From what everyone is telling me I should expect 600+. And wondering if it's worth running my 3.90 gear or getting a 3.73. I have suspension mods and 26" slicks to help the car off the line. But will i be able to launch the car hard once the suspension is dialed in or will I be fighting for traction. I may switch to a 28" slick in the future though.

On the street I'm switching my tires to a 305/45-18

Shoaf85

I say run with the 3.90 gear

I've had 3.90 gears in two of my previous vettes and loved it. Will also help you get into boost quicker since its a centri car. If it were a turbo car I'd say no.

4DRUSH

3:90 gear is the ****

Qkslvrc5z

So I've heard, but how well will it work with 600+ whp

Tar Heel

We're not at 600 (YET!) but that's about the goal when we go H/C/I along with our nitrous. Over 500 now and we love the 3.90 gear! Car is very quick leaving NA (1.50 60' with bolt-on LS1). We also run a 295/50/16 Hoosier DOT drag radial which is just shy of 28". If I had to do it again I might even go with the 4.10.

Scott

marvinseah

I've got 600+rwhp with 3.90's on my car. Car is very responsive down low and pulls like a freight train up top. Only problem is with traction. Even with Toyo drag radials it'll spin through 3rd. I'll give M/T's a try next. Car is a blast to drive with those gears though!

Qkslvrc5z

Do you have any suspension mods? I plan to run m/t's next, what size tires are you running?

marvinseah

I'm just lowered on stock C5Z suspension. The current tires are 315/35/18. I'm thinking about trying some 28" M/T's soon. If it grips I think it'll be a good run for my FBO/E85 GTR.

Qkslvrc5z

I'm putting adjustable shocks, pFadt rear sway bar. And a 305/45-18 mt soon.

LSOHOLIC

Can someone explain this 3.90 superiority generalization.....how's it better than, say a 4.10 or even a 3.42 ??
Aside from the ring gear strength argument.....





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Qkslvrc5z

Really just personal preference for what you want to do with the car. How big your tires are, the horsepower your car makes.

Tar Heel

When we changed from our stock converter/3.42 gear to a Yank SS4000/3.90 we picked up a solid 1 second in the 1/4 and the car felt completely different. Much quicker, better throttle response, seat of the pants feel was incredible! 4.10 may be a little too much depending on the rest of your combination but if the cam, tires and converter was properly matched I could only imagine how awesome it would be!

Scott

Big Jt

Quite simply.. gears make everything work easier.. when things work easier, they move faster.. faster is always good... if you have a traction issue.. then fix that.. it not the gears fault

Also, 3.90's from say 3.42 should be a direct swap with no shims required.. but always check the back lash to make sure.

Shoaf85

LOL I see what you did there LSoHolic
More torque baby. Run as much gear as you can without hitting limiter in 4th gear at the finish line. Since you already have 3.90's roll with it.

This holds true on nearly all setups minus some turbo cars (due to the huge midrange torque numbers).

directnosfogger

the shop i took my vehicle to have drivetrain rebuilt suggested against 3.90's with the z transmission. i'm running 3.73's on my setup now. close to 550, but i'll be looking at more once i can get away from a p1. pretty happy with the results.

Qkslvrc5z

Well my plan for now is to run the novi 1500 with my stock motor for a while then eventually build a forged ls3 (possibly 416). And just crank the boost up. So 800+ is the final goal.

LSOHOLIC

LOL...yup

Gear affects everything......

torque converter behavior
blower speed
blower acceleration
shift recovery
psi recovery after shift
etc..etc...

With enough rpm head room and or tire.....gear is always your friend. Not to mention the performance advantages of the rpm and taller tire have themselves.

And the most important aspect of all (just like Shoaf85 said), torque at the rear wheels.....its really all that matters.



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Shoaf85

PEETYZ

With manual are you talking with MN12 or MN6 ratios? I assume MN12. I have the MN12 on the stock 342 ratio with 27inch tires and want longer gears. The C6Z06 and Zr1 seem to have the best overall gearing over 600rwhp. LS7 bud ( nasty NA C6Z) did swap out to a 3.90 for the track

I know by dropping down to a 26inch tire i could help the slight dead sport after the 3-4 shift but that makes all the gears shorter I don't really drag race but do run 1/2 mile events and a few mexco runs

Lloyd Christmas

My car has stock gears with an M6. 600hp. I could see maybe M12 gearing being fun, but 3.90 or 4.10? With the way this thing tachs from 4k-6.5k, I can't imagine even trying to hold it in the road. It already gets twitchy on a strong 3rd gear downshift, which is slightly more than optimally exciting at hwy speed. Of course, I still run crappy tires too. Loved my 4.11 in my 2000 SS.