3.73s and top speed

[CamaroBill]

All right, guys, let's air this one out. I'm thinking real seriously about going to 3.73s. Only reservation is what people (none with gears) have to say about losing acceleration at higher speeds and giving up some top speed.

Here's my personal theories why I don't think I could lose doing this mod but I can certainly be persuaded that I'm full of sh*t:

1. Acceleration will be stronger out of the hole, around town, and out on the highway. Reason being the only time that acceleration should suffer (overall gear ratio being lower) would be that 20% or so of the time that you would be in a lower gear with the 3.23s.

2. Top speed would suffer little to none. Reason being top speed is not obtained at redline. I do believe that horsepower is the limiting factor and that top speed is limited by the amount of horsepower you have to overcome wind and rolling resistance. If gearing were the culprit, we would reach top speed in 5th gear. I've had my car maxed out once at around 122 - 123 mph. Putting it in 5th gear droped the RPMs but didn't affect speed. Dropping into 4th raised RPMs back up but my speed didn't change.

3. Even though it is a different animal all together, gears in my SS made the car much stronger at all speeds and yes, that includes on the highway.

Any arguments welcome and encouraged!

[michael]

i got a question, i know someone that says if i was to get 4.10's i could hang with some v8's as in gt's and z28's bone stock ones of course.

[James]

I may get flared at about this by some but every stock GT i have seen manual or auto they were running high 14's to mid 15's z's run mids to low 13's stock according to driver I dont think 4.10s will put u there unless u already r running really low 1/4 how ever if u could get it to hook u will take a LS1 owner on the redlight to redlight race but after about 40 he will scream by u like a raped ape

[Cale]

Bill,
I agree 100%.

I added 3:42 from 3:23 to my M5 and DEFINATELY feel that there is no reason why I couldn't of gone with 3:73. The only possible downsides I see are:
1) Traction out of the hole (if it matters).
2)In the 1/4 Mile. You're gonna shift to 4th unless you can get the rev limiter raised another 500 RPM.
3) Highway gas Mileage. In town gas mileage can be combatted by shifting earlier and keeping it easy on the rate of RPM climb. Highway gas mileage could be combatted by driving around 55MPH.

do it and and let us know

[Andy]

so what is your rpm at 70 mph on the highway cale? I really want to go with 3.73's but I still want to drive down the highway to the track at a reasonable rpm.

[Cale]

On my way home tomorrow I will see where the RPMs lay rest at 70mph. Off the top of my head, the engine is rap'in right around 2K.

[pgriffith]

The reason your car only reaches 120 is because of the speed governer. You say its lack of power but I say its the speed governer. My governer is set at 118

[Slow-N-ugly]

Gearing, all things equal the lower the gear the lower the top speed period. The only way to have the same top speed with 3.23 vs 3.73 is you speed limiter, I am sure with enough horsepower your C.D. would become a factor. Transmission gear ratio should come in to play with motor rpm 4spd vs 5spd. There are alot of factors to consider but as I said "all things being equal" if you go to a lower gear you should get off the line quicker but.....will you have to shift to fourth at the end of the 1/4? could be a slower E.T. You top speed should be reduced if only 3-5mph or more, if your top speed is limited by some factory installed device.

[GordSipko]

More gear = more acceleration!

Switching from 3.23 to a 3.73 is a 15% change. You will see 15% more acceleration throughout the entire range. Your engine will also be spinning over 15% more than it currently is so you will see a higher rate of wear. If you're currently turning 2000 rpm @ 60 mph the new number will be 2300 with the gear change. An old 3000 rpm speed now becomes 3450, etc. You may or may not see a top speed change as top speed is a balance of forces - aerodynamic and driving force.

Aerodynamic forces vary as the square of the speed. Driving force is determined by engine torque (varies with rpm), gearing (trans and rear axle) and the effective radius of the drive wheels.

If you knew your current top speed (and it's not ECU limited) and had a torque curve for the engine, it would be possible to estimate the new top speed after the gearing change.

[6Banger]

Check out the calculator at this site to determine RPM based on gears, speed, and tire size. I hope it's helpful.
http://www.fbody.com/calc.htm

[CamaroBill]

When I did my top speed run (on a straight flat road with no traffic) and hit "only" about 122 - 123 mph the speed was drag limited. I have HPP3 and have the top speed limiter at the max. it would allow (something like 167 mph). Sorry, guys but our cars do not have high top speeds due to lack of power to overcome drag (wind, drivetrain, etc.). Of course when I made my run it was when the car only had about 1,200 miles on it so it might be a little higher now since it is more "loosened up".

I guarantee you, though, that you will hit your top speed before your engine gets to redline unless you have really steep gears (like, maybe 4.56s) or lots of horsepower.

[xzeppelin_manx]

GordSipko is right about the gears.

The governer is the reason we top out at 120(because the rating of the stock tires). Wind resistance isnt going to stop us at 120, and wind resistance wouldn't stop you that abrumptly, i'm still pulling hard when i hit the limiter and you can feel the car slow down all at once when you hit it.

[Blue Flame V6]

Your car will do @ least 125 mph. My sisters stock Monte Carlo SS does that and it is still climbing when it hits the governor. That is a A4 3.8 so there ya go.

[Patrick Javert]

I think that you should get the gears. If you really hate the highway gas mileage, then you can get something like ZO6 vette rims that are 18x10.5 and put Nitto 555 series tires that are 295-45-ZR-18's on. Also, the more weight on your car, the more hp you need to get it to stay at highway speeds. get a lightweight k-member, get a aluminum 1LE driveshaft, lose the spare tire and jack, and get a lightweight ram air hood. These will all help in lowering highway rpms.