I'm thinking about buying a center section locally which is fitted with 4.30 rear gears. My question is, how "streetable" are 4.30's with an m6? I do a lot of highway driving so I don;t want the rev's to be too high (I also have some REALLY loud exhaust) What kind of RPM can I expect with stock height tires in 6th at about 60-70mph? Would gas milage be greatly affected? Is first gear useless in everyday street driving?

Thanks

Andy

 

I have 4:30's with a 400+ RWHP car and a M6. I wouldn't say that 1st is totally useless, but it sure revs up really quick. 6th gear on the highway is manageable at highway speeds, I wouldn't want to do any top speed runs or anything with them but it's certainly manageable, I'm not sure off the top of my head what RPM's but it's probably somewhere around 2K or around there - 6th gear becomes much more useable. Because you are turning more RPM's your gas mileage will suffer some. That's just how it goes.

If you're going to run these gears on stock rims with decent power, do yourself a favor and run Nitto drag radials or something because with the stock F1's and a full suspension even it will blow the tires away in almost every gear through 3rd on my car with the stock rim/tire setup. I run Hoosier DOT's most of the time.

For dragging, stoplight racing and races from a slow roll they are really fun and the car revs really quick. If you have a peaky motor/aggressive cam the gears really help get the car into it's powerband much quicker.

 

Wouldn't want to do top speed runs with it?

It's still good to 220+ mph!

How fast do you want to go?

Anyway, to answer your question, you'd be at 2000 RPM @ 70 mph, 1700 RPM @ 60 mph.

http://www.xse.com/leres/bin/gearrat...mference=80.90

That link is very cool. Mess with it a bit. Like from there, you can see your shift points would be 42 mph in first and 63 mph in second.

 

Am I off base here or something? I'm running an M6 with 3.23 gears and I am running 1600 rpm at 60 mph or so in 6th gear... So how could it be 1700 rpm @ 60 with 4.30's?

 

I have that setup. Running MT drag radials to try to get some traction. First gear rapped out really fast in first. I hit the limiter if I wasn't careful. I have since switched to a 28" tire. Car is down right now though.
So for the record, if you trap above 116-117 at the track, 4.30/6speed and 26" tire do not mix. I was shifting to 5th 100 ft before I crossed the traps.

 

Also to add, my gas mileage sucked. I think I turned about 2200 rpm around 70. And with 400+ rwhp, I could spin the tires in third.

 

Let me guess... you're running an LT1 with 3.23s and an M6? Because LS1 F-bodies came with 3.42s stock.

If that's the case, the reason why you're running at 1600 rpms at 60 mph is the gear ratios in your transmission are different than the ratios in an LS1 F-body.

LT1 F-body:
1st - 2.97
2nd - 2.07
3rd - 1.43
4th - 1.00
5th - 0.80
6th - 0.62

LS1 F-body:

1st - 2.66
2nd - 1.78
3rd - 1.30
4th - 1.00
5th - 0.74
6th - 0.50

At the same speed, an LS1 F-body will turn lower rpms than an LT1 of the same rear end gear ratio. So while 3.23s in your car means you're doing 1600 at 60 mph in 6th, if an LS1 F-body with an M6 had 3.23s, they'd be doing 1300 rpms at 60 in 6th.

That difference in transmission ratio is the reason an LS1 F-body (M6) equipped with 4.30s will be doing 1700 rpms at 60 mph in 6th, while you're doing 1600 rpms at 60 in 6th with your LT1 and 3.23s.

 

I used to run the 4.30s with a 275/40/17 tire on my old car, and loved it on the street. Never went to the track though, then I sold the car.

Now I am building another car and tore my rearend up at the track this past Sun. on Nittos and the stock 10 bolt with 3.42s in it. Now my question is how are you trapping with the 4.30s and a 28" tire? I was thinking of ordering some 4.30s in the 9" I am gonna have to get.

Thanks, Dave

 

Haven't ran the car at the track since I switched tires. I'm guessing the taller tire will get to 120 before needing to hit 5th.

 

Tire question... I have 4.11's and will be buttoned up this weekend. I'll need to get new rubber anyway, would you step up to the ZR1 x 11" in the rear or stay with the 17'9 Firehawk rims with Nitto's? What is the best tire?

 

11's weigh a little more, but you can get more tire on it. If you can hook with the skinnier tire, then you're good to go. If not, bigger wheel and wider tire. But to be honest, an et street or MT drag radial on a 17x9 wheel should be good enough. I ran et streets on a 15x8 for a long time and could hook ike mad.

 

Why no top speed runs? Because you'll run out of gear?
Theres a cool vid on firehawk.org of a guy runnin 4.30s and it seems pretty slick.

 

i love my 4.30's. i run a 26" (275/20/17) on the street and a 28x9x15 et drag at the track. i turn roughly 2100-2300 cruising on the highway 73-78 mph

only thing i dont like is you cant do any high speed races cause you run outta gear at like 120 mph with a 6600 limiter

 

How do you run outta gear ? Like 120 in 4th, then like 160 in 5th, then like 240 in 6th ???

 

5th on the highway loses all kinds of pull because its an overdrive gear

 

6600 in 4th to 5th rpms drop to 4950. Mine still pulls pretty good at that RPM

 

Mine too

 

When you say if you run faster than 116-117 at the track....Are you stock internal or have you installed a cam? What do you turn your motor? Or maybe I should ask, at what rpm do you shift?

Thanks, Dave

 

I run 1700rpms with my 3.42's in 6th @ 70mph in my 00' TA. Lt1's came with 3.42's too, except the 93's, which came with 2.73's and 3.23's.

 

heads/cam. I have the rev limiter at 6700. Going to 6900 would have possibly got me to the traps in 4th. But my peak power was at 6-6200 so I want to be going through there or just past there in 4th.