Speed and Gears
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TECH Apprentice
Joined: Oct 2003
Posts: 396
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From: Lumberton, TX
Speed and Gears Why do 4.10's hurt top end speed? In 3rd gear on up, I can pull a M6 with similar Hp as me, but he has 4.10s. Also raced a head and cam car with 30 more hp than me and we lock in at 3rd and 4th. So why do they hurt top end speed?
Launching!
Joined: Jan 2004
Posts: 273
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From: Trois-Rivières (Québec / Canada)
Originally Posted by setxws6
Why do 4.10's hurt top end speed? In 3rd gear on up, I can pull a M6 with similar Hp as me, but he has 4.10s. Also raced a head and cam car with 30 more hp than me and we lock in at 3rd and 4th. So why do they hurt top end speed?
With 4.10's you will hit the rev limiter in 5th gear at a lower speed than you will do with 3.42's.
Actually, on a stock car, 4.10's could increase your top speed. When my car was bone stock (299rwhp) with 3.42's I could not even reach the limiter in 5th. My top speed was 141mph and the engine had nothing left to go faster. When I switched to 4.10's I was able to hit the limiter at 152mph in 5th (and it was still pulling).
Now if we're talking modified car, yes 4.10's will limit your top speed (unless you raised your limiter, assuming the valvetrain can hold it). No matter how much rwhp you will produce, you will hit the limiter at the same speed in 5th. Unless you have a real high-power car (say 800+rwhp) that could actually use it's 6th gear over the 5th in high speed application.
I actually run 3.73's with a 6400rpm limiter. So, my theorical best top speed should be 177mph in 5th before hitting the limiter, assuming I have the power to go there. I never tried yet (and probably never will
) but it should be close. I have 100 more rwhp now over my stock setup.I mainly choose 3.73's over 4.10's to regain some traction in 2nd, but that also increased the top speed of my car because of my engine mods. But with a stock engine, I would probably have lose top speed with those gears.
Hope that help.
Question though: My 2002 topped out in 5th gear the day after I bought it. I actually hit the speed limiter with the needle buried past 155. That was when I still had the 3.42's 
