Gears for turbo street car

[twinturbo69]

I have always been told that turbo motors like load on the engine and I am looking for 3:23:1 gears for a Chevy 12 bolt, though having a tough time finding them anywhere. I know that this ratio is available in the much smaller 8.5" 10 bolt rear, but the closest options I can find for the 12 bolt are 3.08:1 and 3.42:1. Appreciate anyone pointing me in the right direction. The car will see the track every so often with the majority of driving on the street. Car makes 800/800 with torque coming on strong down low. Trans is a Turbo 400 and I recently acquired a Moser 12 bolt with 33 spline axles.

[LS1NOVA]

With no overdrive, go 3.08's. Im running 3.42's with a 4L80E with 650rw. Lots of guys go even higher, like 2.75-3.00 range.

[looter]

how do you like the 3.42 with the 4l80?
would you do it differently?

[LS1NOVA]

On a 6.0 Id prob go 3.08's for super easy 80mph freeway cruising. On mine the boost came in so fast that it really had no chance of hooking on 17" drag radials. Im running a 5.3 now so the 3.42 are staying since it needs a little help down low.

[mnm99]

I have 3:25's

[SS PUNISHER]

Go with 3.08s unless you are runnin a super tall tire

[shmoov69]

I got 3.00 in my 9" with a th350 and love them. Somewhere around that would be my choice.

[RSX302]

I haven't run turbos on a auto trans, but I would have to guess it's all about the turbo size, converter lock up rpm and tires. Without overdrive and top gear being 1:1, I would think lower the better with your 800lbft. (tire spin is a big factor on street tires)
At 70 mph, 3.08's on a 27" tall tire is ~2600-2700rpm, 2.73 is 2300-2400rpm. Size converter accordingly.

I run 3.70's on a manual 6sp which is about 70mph at 2000rpm. Nice cruiser! 700lbft pulls 6th no problem.

[twinturbo69]

Thanks Ron and everyone else for their input. I will likely go with the 3.08 gears as the cars comes on boost almost off idle with the T04B's (60mm). I will likely run 27" tire height and have a 3000-3500 RPM stall converter. If I have a problem putting the power down, I will go even higher on the gearing as everyone is suggesting. I am considering going with a gear vendors unit down the road, though 2600-2700 is livable at 70 mph on the street.

[shmoov69]

Sounds like it will be a tire fryer!! Or at least thru first gear...and part of second!! LOL. Mine is really a complete waste to "rip hard" thru first gear unless there are slicks on it. How's yours do down low Ron?

[RSX302]

Thanks Ron and everyone else for their input. I will likely go with the 3.08 gears as the cars comes on boost almost off idle with the T04B's (60mm). I will likely run 27" tire height and have a 3000-3500 RPM stall converter. If I have a problem putting the power down, I will go even higher on the gearing as everyone is suggesting. I am considering going with a gear vendors unit down the road, though 2600-2700 is livable at 70 mph on the street.

Again, I'm not an Automatic guy, but seems to me 3500 stall would be a little on the high side for a street car. Wouldn't the rpm at 70mph be your stall rpm?

I was thinking closer to 2500-3000 max stall?

[RSX302]

Sounds like it will be a tire fryer!! Or at least thru first gear...and part of second!! LOL. Mine is really a complete waste to "rip hard" thru first gear unless there are slicks on it. How's yours do down low Ron?

I have Toyo R888's and outdoor temp decides grip. 80deg day hooks very nice in first/second. Can always get first to spin depending on the throttle (easily controlled), but second is planted. Now 50degs on the otherhand is a handfull.

Overall driveability is spot on.

[shmoov69]

Cool, I wonder if mine spins so bad because of the tall gear, especially since you prolly have more power? With the six speed, you are shifting alot more and not having to try to stay in gear as long as me...just thinking out loud, don't know if that is legit.
My converter is a TCI Super Streetfighter that I had them tighten up a bit. It will flash stall to 3500, but has VERY good part throttle lock up. I would definately suggest a good converter since you will be driving it a bunch.

[INTMD8]

3.31 is available for the 12 bolt. May need to find original/used as I'm not sure if it's made anymore.

[RSX302]

Cool, I wonder if mine spins so bad because of the tall gear, especially since you prolly have more power? With the six speed, you are shifting alot more and not having to try to stay in gear as long as me...just thinking out loud, don't know if that is legit.
My converter is a TCI Super Streetfighter that I had them tighten up a bit. It will flash stall to 3500, but has VERY good part throttle lock up. I would definately suggest a good converter since you will be driving it a bunch.

I don't think your tall rear end gears are your tire spin problem. More so the 3500rpm flash stall, tire and suspension. What's the true stall? When you take off from a stop, you instently jump into your engines peak torque power range. What's your cruise rpm at 70mph?

With a manual trans you can control rpm and clutch slip and drive thru the lower rpm to get the car rolling before peak torque kicks (or try to..lol). If I rev to 3500rpm and drop the hammer, I too will blaze the tires no problem..even with the Toyo's. Before the Toyo's, I had 335 Michelins. I had to leave the tree at 1500rpm and let it drop on its face, pull back up thru the gears to get a decent time slip.(11.6 at 127). Anything else resulted in major tire spin half way down the track. I didn't try the 2nd gear start. Couldn't get myself to lean on the clutch like that.

I was reading up on stall..One quick article I thought was intresting.
http://www.carcraft.com/techarticles...ter/index.html

[shmoov69]

My converter does partial lockup very well, so "normal driving" it will leave a stoplight around 1500-1800 and cruise at 70 around 2500 (if I remember right?). But with the tq, it flashes the converter pretty quick and hits hard when boost comes on.
The tires are Nitto 555's in a 255/50/17 and I got a 3.00 gear. My best times at the track was on 27x10 ET Streets and was a 10.97 @ 125 and change with a 1.80 short time. That was with the old turbos also. The new times should be considerably quicker if I can keep from breaking it.

[RSX302]

My converter does partial lockup very well, so "normal driving" it will leave a stoplight around 1500-1800 and cruise at 70 around 2500 (if I remember right?). But with the tq, it flashes the converter pretty quick and hits hard when boost comes on.
The tires are Nitto 555's in a 255/50/17 and I got a 3.00 gear. My best times at the track was on 27x10 ET Streets and was a 10.97 @ 125 and change with a 1.80 short time. That was with the old turbos also. The new times should be considerably quicker if I can keep from breaking it.

Looks like you have good traction with slicks..lol

From what I'm reading and what you are saying, it sounds like your converter is somewhere around 2500-3000 True Stall and 3500 Flash Stall?

You using Nitto "Street" 555's? Many year ago I had 255 Nitto's (not 555's)on my 93 mustang with a Kennebell blower (400ish rwtq) They were decent tires but had a tough time getting off the line in first and second. Now I use tires with treadwear rating of 80..The 335/30/18 Toyo R888's get the power down well on the street without going to a drag radial. Haven't tried at the drag strip yet to see how they would do. Soon!

[shmoov69]

Looks like you have good traction with slicks..lol

From what I'm reading and what you are saying, it sounds like your converter is somewhere around 2500-3000 True Stall and 3500 Flash Stall?

You using Nitto "Street" 555's? Many year ago I had 255 Nitto's (not 555's)on my 93 mustang with a Kennebell blower (400ish rwtq) They were decent tires but had a tough time getting off the line in first and second. Now I use tires with treadwear rating of 80..The 335/30/18 Toyo R888's get the power down well on the street without going to a drag radial. Haven't tried at the drag strip yet to see how they would do. Soon!

Correct on the converter. It hooks pretty good with the slicks, it will wad them a little about 60-100' out when full boost comes in. That was with the old turbos, so I'm not sure when I crank on the bigger ones!
Tread wear of 80?!!? Man, how long do they last?!?! Do you have to change them at every oil change?!? LOL.

[RSX302]

Correct on the converter. It hooks pretty good with the slicks, it will wad them a little about 60-100' out when full boost comes in. That was with the old turbos, so I'm not sure when I crank on the bigger ones!
Tread wear of 80?!!? Man, how long do they last?!?! Do you have to change them at every oil change?!? LOL.

Since I don't use the Camaro as a daily driver, the Toyo's at 80 treadwear actually last pretty good. I've run on the street for a year and they've seen heavy track use a couple of times at Willow Springs.

[twinturbo69]

Thanks for inputs on the converter sizing. I'm not the most knowledgeable in that area and appreciate the information. I do plan to shoot for low 10's at the track and do want the gearing and converter sized to accomplish this goal. I won't drive the car all that much on the highway and can always change the gearing in the future should that change. Torn between 3.08 and 3.31 though I know the latter is more consistent with what I need to run the times I want at the track and should equate to less stress on the drivetrain. Based on what I see in the market, I need to go with Nitto's for street tires to get the higher 40-50 sidewalls to have my car sit right to launch on the Caltracks and split monos. At the track, I will run 15-16" rims with drag slicks to get as much sidewall to launch on as possible.