Abby Normal

It would depend on the gear. C5's can come with 2.73,3.42, 3.73 and I think 3.15 from the factory. So depending on that, Mark could be correct.

mark kibort

You have to read more carefully. the numbers came from , limited to 6500rpm and using a 3.73 rear end. actual gears: 2.29,1.61,1.22,1,.85,.75:1. thats where the numbers came from (also using a 25.5" tall tire) This was done so we could compare the apples to apples if you used a vet trans, in a 928.

however, again, it was clearly stated that the rear end compared was the common 3.73 rear end. yes, it would be 6900rpm in first to get 62mph, but i think the rev limit on a zo6 is in the 6300rpm range.

as was stated as in another post, there are several selections of rear ends. I used the most common by most Zo6 owners and new C6 owners.

MK

mark kibort

2..72?? that would be an ugly box with the C6.

79mph 1st gear, 113mph 2nd gear,149mph 3rd gear, 182 4th gear, 215 5th gear. 245mph in 6th!

you would loose a gear between 1-2nd compared to normal and then, loose the mid range extra gear too, all at a cost to get to 250mph. doesnt sound one of the reasons to us a T56.

Also, there is an option for a 4:11, but that yields:
52, 75, 99, 120 142 161MPH. Now, that looks like a great box for road america!!! as long as you had less that 500hp at 3000lbs.


mk



AS FAR AS THE BOTTOM LINE WITH THE GEAR BOXES

redline call it 6500rpm for the GT vs S4 vs VET Z06 is :

VET /3.73:1 --------- 58,83,109,133,157,178 MPH 1-6th gears
S4 /2.2:1 ------------ 55,84,117,155,224 MPH 1-5th gears
GTS /GT 2.72:1 ---- 49,73,104,138,183 MPH 1-5th gears

Abby Normal

Doubt it was ever offered in a C6. It's early C5's and I think it's 2.72 or 2.73, not really sure. You can get a lot of after market gears with HD shafts also....

mark kibort

Im just going off the C6 and C5 speedGT spec for the production car.

I think those numbers are from the C5, as they may have not gotten to the updates (if any ) on the C6.

Mk

Chris Lockhart

I was wrong about my rpms at 75 mph. I am running 3100 rpm at 80 MPH.

Mark, like someone mentioned previously, we are not all racers out there looking for race gearing. There are other factors involved, and I DEFINITELY think your Corvette numbers are skewed. I have a friend who has a C5, and he claims that in 6th gear, @ 75 MPH he is only showing about 2400-2500 rpms.(and I have no reason to think that he wouldn't tell me the truth) To me that is a huge improvement when compared to my 3100 @ 80 mph. Less rpms= less wear and better fuel economy. PERIOD!!!!!!!!!!!!!! You look at things from a racers view, I look at them from an everyday driver practicality standpoint.

mspiegle

so regarding the original topic... what were the main reasons a 'vette tranny woudln't work in a 928?

jpitman2

Chris, "less rpm is less wear, better economy.." - maybe true for wear as long as you are not lugging it, and not always true for economy IMHO. If going up a gear takes your rpm down the torque curve your economy will get worse, not better. Try early changing into 5th consistently, and I think you will see this occur - I have.
jp 83 Euro S AT 49k

Chris Lockhart

[If going up a gear takes your rpm down the torque curve your economy will get worse, not better. ]

JP, I agree that if you're lugging the motor, it's not efficient. My statements were based on steady state highway cruising. 2500 rpm will return better fuel economy than 3100 rpm.

I love Mark to death, but virtually every discussion that comes up, his input is with a strictly road racing view. We are not all racers, and have differing needs/opinions about what performance is best for what we're looking for, not necessarily what is best on a racetrack.

Ketchmi

Chris, I doubt that Mark will ever figure that out as it has been presented to him at least a dozen different ways and he has not listened yet. I am a racer but I can easily see the relationship between lower gearing and acceleration (straight line, limited distance) for a street driver. I like Mark also but he is just right, always, dammit, just ask him! (Bwaaahaaahaaaa)

Chris Lockhart

LMAO Dave. You're right on the money!!!!!!!!!!!!!!

mark kibort

Chis and Ketchmi,

Again, i posted the ACTUAL values. (as I usually do.) your friend, unless he has a special transmission, has the following ratios. this results in the numbers i posted for speeds.

Lets clear up another issues. Im not posting my numbers and information from the perspective of a racer ONLY. ive posted them for best acceleration, for all applications. IF we are talking driveability, thats something different. I personally , like many, like the low rpm, high torque engines, so you get adaquate acceleration on the street , but very low RPMs and subsequently, lower wear over time on your engine. If we were talking ONLY racing, the gearing ratio is more cut and clear, especially when talking about drag racing.
Drag racing with a target speed of 115mph, would want a gear box that gave you redline in that final gear.

BUT, and Ill say this again too. GEARING doesnt buy you acceleration OVERALL. it can for separate segments, but for some reason, you dont get it . (ketchimi, not you chris). Just getting a taller rear end shifts ALL the shift points right. so, there will be trade offs over multiple shifts. DEPENDING on your target speed, gearing will effect the torque to the wheels over that range. (ie 0-80 may be better with the lower numerically ratioed gear end vs a target speed of 60mph, which may (does) favor a taller rear end). the faster top speed, the more of an effect this will have to the target speed.

I can post the actual numbers til im blue in the face, and its not a matter of thinking im right, this is simple stuff. Like i said, i often sit in a room with PHD'ed engineers discussing issues, and re-educating them directly related to this subject matter. (most of whom have forgotten more than ill even learn in my lifetime!) It may be best for you to stand back and think for a second what im talking about.


chris, you also need to re-read my post too. the rpms were for 80mph and it was in the 2900rpm range for both a GTS and a vet. you posted 2600rpm for your fiend at 75mph and that sounds about right, doesnt it??
This means that there would not be any difference between the C5 box and a typical GTS gear box as far as the final drive ratio. last time i looked the C5's 3.72 x 6th gear of .75 = 2.79 and the GTS final drive is 2.72. pretty darn close and hardly worth a gear box transplant. (unless it was for the better torque strength of the C5 box that was mentioned!)

MK



You have to read more carefully. the numbers came from , limited to 6500rpm and using a 3.73 rear end. actual gears: 2.29,1.61,1.22,1,.85,.75:1.

mark kibort

right from Car and driver, the new C6 has an interesting gear box
2.97,2.07,1.43,1,.71,.57 all through a 3.42 rear end. and guess what, the 0-60 times are still 4.3 and 1/4 mile is 12.7 compared to the 400hp z06 of the C5 with entirely different set of ratios.

NEW C6:
49mph 1st gear
71
102
147
204
256mph with a real 6th speed overdrive ( 165mph at 4200rpm)

at first glance, this is really a S4 gear box, now with 2 overdrive gears and a little lower set of 1st 2nd 3rd 4th and 5th. just different compared to a GT 928.

The gears I quoted previously were from the c5.

mk

heinrich

Yep. One always has to read Kibort's posts more carefully. I find after a couple 3 Lagavullins or MacAllans, if I pull the shades and hold Mark's post just so, I start seeing pink hefalumps in tutus dancing ALL OVER the paper

BC

Funny you should mention Hefalumps H. My wife found an english version of Poobear with Judy Dench, her TV husband *forgot his name* as Eor, and the crazy blond from AbFab as Piglet. Eor is halarious. Its in the DVD changer in the MDX at all times.