[mikewebb1514]

Hi all.

Let me start by saying the only performance car I have owned so far, was a '69 Roadrunner with a 383ci, 4 on the floor and 3.23 gears in the rear end, a nice all around muscle car. (I once put 4.11 gears in the Roadrunner and what a difference that made, awesome off the line but sucks on the freeway.) I am planning to buy a used '99 or '00 Corvette next spring and I want to use my experiences with the Roadrunner as a starting point in picking a good transmission / rear end gear combination. (Only 2 possible rear end gear choices available with the 6-speed transmission, right?)

My question is...

Does the 6-speed transmission act like a 4-speed that has the traditional 4 forward gears (in this case, gears 2,3,4,5) with an additional lower than normal gear (1st) and an overdrive gear (6th), higher than the 4th gear in the 4-speed? (In which case you would get great off the line performance and great freeway driving / gas mileage.) Or...

Is the 6-speed just 6 gears matched to the 4-speed’s range of gears? (No extra low 1st and no overdrive.) In which rear end gear selection would be more critical.) What is the advantage to this setup?

The reason I ask is I hear some Corvette owners talking about how it really makes a difference to get the performance rear end gears. Also, how badly does the rear end gear selection effect the mileage?

Mike:smokin:

 

[The Torch]

The performance axle is available with the A4. The standard is a 2.73 and the perf is a 3.15. The M6 comes with a 3.42 Some A4 owners swap to a 3.42 when the M6 owners go to another gear like a 3.73. In the M6, 4th gear is 1.00:1, 5th gear is .74:1 and 6th gear is .50:1. This is a whole lot better than the old 4 speeds. Welcome to DC and good luck of the Corveete

 

[JBsZ0666]

Just put in a 3.73 rear gear in my Z06..

Best dam modification to date..

Cars always ready to pounce!

and with this six speed tranny...the car still cruises at such a low rpm...the car is awesome!

Remember fifth and sixth are huge overdrive gear ratios..

I've driven a buddy's C5 coupe heads and cam with 4.10s in the rear gear and it also is totally civilized.

6 speed trannys are a win win!

The CTS V series with the Z06 motor and Z06 M12 tranny are from the factory running 3.73 rear gear ratio...right from GM...

 

[glennm27]

MN6 & 3.42

My coupe is stock as far as the drive train is concerned and runs great. I would imagine the 3.73's would be a real kick though.

As for the gears, I drive it like a 4 speed with the added luxury of having those two top end tall cruising gears (5 & 6) there for highway use and saving fuel when just driving it out on the highway to get from A to B.

 

[mikewebb1514]

Thanks for the information.

Wow, 2 overdrive gears was not one of my thoughts but it makes sense. Now I know how the car gets the top end and why lower gears in the rear end really help off the line.

Mike

 

[urbman]

Changing to 3.73 makes sense, when you are looking purely for acceleration and you have to live with a speedlimit.
When you are going for topspeed (you know: no speedlimit on the german Autobahn. Here it is more usual to compete in the topspeed range than to dragrace from the traffic light) then the 3.73 would be a bad mistake.
My 99 FRC (minor mods: blackwing, throttle body, LS6 intake, open exhaust) makes exactly 6000 rpm in fifth gear with the 3.42 axle, that's 184mph, with the 3.73 this would only be 167mph and when you remove the rev limiter, it would rev to death.
The sixth gear however is way too long, it's purely an overdrive, full throttle in sixth gear will result in a topspeed of about 145mph.
So for topspeed concerns the 3.42 is perfect. I have to say respect to the Corvette engineers for that perfect matching.

 

[JBsZ0666]

GM stated the CTS V series with the 400 hp LS6 and the 3.73's top out at 171 and thats with a vehicle weight of 3800 lbs. (if they do not produce the V series with 155 mph speed limiter to match the german competitors 155mph agreement for limiters.

STock top speed for the 405 hp z06 @ 3100lbs with stock 3.42 gears is ???? 169 to 175mph

Although I won't personally be testing top speed capability of the Z06 with 3.73 gearing I am under the impression because of its lighter weight and superior aerodynamics(of CTS V series) ..should equal or better the CTS V Series..

JMO

 

[JBsZ0666]

Excellent comparative chart:

http://www.shagfinger.com/ratios.htm

 

[fdxpilot]

Changing to 3.73 makes sense, when you are looking purely for acceleration and you have to live with a speedlimit.
When you are going for topspeed (you know: no speedlimit on the german Autobahn. Here it is more usual to compete in the topspeed range than to dragrace from the traffic light) then the 3.73 would be a bad mistake.

Actually, on cars with significantly more horespower, say 400 RWHP, 4.10s on a 6 spd have produced their top speed in 6th, as the car comes close to reaching it's power peak. With 4.10s, 180 is 4800 rpm

 

[urbman]

I don't know the perimeter of the CTS V's rear tires, but let's assume it's roughly the same than the Corvette has.
When GM states the CTS V's topspeed at 171 than this means the Caddy has the MM6 tranny with 5th 0.74:1. If you would combine the M12 of the Z06(5th 0.84:1) with the 3.73 axle, you would run into fuel shutoff at 6600rpm / 162mph.
So again (considering the much better aerodynamics of the Corvette and the rev range of the LS6) the overall drive ratio of the CTS V seems to me equaly perfect than the 3.42 of the LS1 Corvette.

 

[hotmtrsports]

Just got my C5 6 spd back from the dealer with 4.10 installed. All I can say is WOW and WOW again!

You thought 3.73 is ready to pounce!

I've got to let the speedo know it. The dealer says they only have a choice of changing to two possible ratio's. I'm anxious to find out the MPH difference and fuel economy difference.


Talk about SUPERCAR power!

WOW again!

Chuck

 

[JBsZ0666]

I don't know the perimeter of the CTS V's rear tires, but let's assume it's roughly the same than the Corvette has.
When GM states the CTS V's topspeed at 171 than this means the Caddy has the MM6 tranny with 5th 0.74:1. If you would combine the M12 of the Z06(5th 0.84:1) with the 3.73 axle, you would run into fuel shutoff at 6600rpm / 162mph.
So again (considering the much better aerodynamics of the Corvette and the rev range of the LS6) the overall drive ratio of the CTS V seems to me equaly perfect than the 3.42 of the LS1 Corvette.

Just to clarify the CTS V series has the M12 Z06 tranny yet more importantly...

Hotmotorsports...congrats on the gear upgrade..Its a blast!

Have fun with the 4.10's!