Look American, this is NOT rocket science. The drive shaft turns over 4.11 times for each time the rear axle halfsafts and wheel/tire turn over with 4.11 differential. With a 2.73, the tires turn over one time for a little less than three (2.73) turns of the driveshaft. NOW, multiply that by the ratio of the final transmission gear that you are using. In a Corvette, both 5th and 6th gears are overdrive (less than 1.00/1)

 

Sorry, DUPE

 

You'd figure someone with a college degree would get it. I read that a couple of times and drew a picture

so if the drive rear gear 4.11 is less 2.73, then your wheels spin faster? Multiplied by a transmission gear and you get how much the transmission is letting the rear rotate, and that's why at less than 1.00/1 in 5th and 6th the overdrive is basically dead and you just end up getting gas mileage.

because of gearing/trans/clutch you lose power from engine to rear wheels

If you bump the power then 5th gear can spin faster and you'll redline quicker so you reach the top speed faster. Ah, and that's why the fastest you can go is redline in 5th but you can get there faster. right?

Hey I might sound like an idiot, but dang it I'm gonna be a car guy and to get there I gotta take my lumps. I'll admit it.

 

This might help a bit. Back when automatics had 3 gears and no overdrive, the rear gear ratio determined alot of the performance. A 2.73 car will have great gas mileage, it will be slow in the 1/4, but will seem to have endless top speed potential like 150mph. If you switch it to a 4.11, driving down the highway the engine is roaring 3K rpm, so gas mileage sucks. The top speed would be limited to around 100mph, but it would wind out and get there quick. Now we have ultra overdrive ratios available in the tranny, so we can have the 4.11 rear gear and decent mileage too. Combining different tranny OD ratio, rear gear ratio, and tire height, you can do many different applications. Oh, the Z06 rear ratio is 3.42. Our Hummer H2 has 4.10, that helps get that big heavy butt moving, and especially if towing.

 

Chris,
I run a ZF tranny out of a C4. Now it has cryo frozen gears and a tranny cooler for running at speed for distance without melting down. I have 3.08 rear gears. When running I use 5th gear (.75 I believe), 6th is too high I can't hold much more then 170 with it. With this combo I am turning 5500 rpms at 200mph.

Jason,
Cool video. I can see why you only go up and touch 200 since you are turning 66-6700 rpms. That is moving right on down the road.

Jeffy'

 

that wasn't sixth gear, he has a coupe m6 transmission, that was the redline in 5th gear.

 

Sometmes a picture IS worth a thousand words .....

Maybe this will help ... think of a car with NO TRANSMISSION ... just an engine and a differential connected by a drive shaft (which in 4th gear is effectively what you have in a C5 Corvette). If my rear end ratio is 2:1 then that means that the engine spins twice as fast as the output shafts on the differential. If my rear end ratio is 3:1 then the engine has to turn over 3 times for every turn on the output shafts.

What makes this more complex is the diameter of the wheel/tire combination that is at the end of the output shafts. If I have a tire that has a circumference of 30 inches, then every time the output shaft spins once, the car travels 30 inches of road. If I have a tire that has a circumference of 50 inches, then that same turn of the output shaft means the car travels 50 inches of road ... so .... while differntial ratio makes a difference ... so does wheel/tire size.

Throw the transmission into the equation ... and to some people you are looking at "rocket science" .....

Think of the tranny/differential combination as a way to let the engine gain "leverage" ... and remember that with a big enough lever a human could lift the weight of the earth.

Gearing, in both the gearbox and differential, is simply a way to allow the engine to run in its "power band" over a wide range of road speeds. We can select these ratios based on many choices ... fuel mileage, acceleration, top speed .... and if you choose one, you loose on the other two. A car that gets GREAT fuel mileage is not geared for top speed or acceleration. A car geared for acceleration gives up top speed and fuel mileage. A car geared for top speed is not going to accelerate or get the fuel mileage of the other two.

Yup ... and auto makers spend mucho dollars on trying to reduce the friction losses in the tranny, differential, and other parts of the drive train because any gain they make delivers more power to the wheels. That means better acceleration, top speed, and fuel mileage.

Basically you're right ... if you increase the engine's torque output, you'll get to redline faster.

The only idiots are people unwilling to learn ... you don't seem like an idiot to me ....

 

Well put

In my opinion an m12 built with an m6 5th and 6th gear, with 3.42 rear end is the best balance of those three things. or if you want to go with better performance and top speed, but are less concerned with gas mileage then go 3.73 rear with m12 that has m6 5th and sixth. After all you still get 25+ mpg anyway. With the power levels I'm shooting for I don't feel 3.73 and the m12 1,2,3 gears are gonna be my best bet. Although 3.73 and a standard M6 would be a good setup also, and probably cheaper than a modified m12, unless you need a built tranny anyway.