Are 3.55s The Best Gear for the 2011 5.0L GT?
 

Taking a look at the Car & Driver test from this month. States that the redlined mph limit in the 3.73 equipped GT is 110mph in 4th gear. Since most other magazines are hitting 112mph, might 3.55s be the best option for gears from the factory, particularly if you are able to squeeze a couple of more mph out of it with the bolt-ons that are sure to find their way on these cars? That 3.66 first gear and 1.32 4th gear are pretty steep.

:dunno:

The best gears are the ones you are happy with based on your particluar driving style and future plans for your car.

What difference does 4th gear make?

3.73 is going to give best street performance, just shift it into 5th when 4th runs out, 5th gear is 1:1 not overdrive.

For strictly drag race performance a 4.30 gear would be the hot setup.

Sure, but which gear is better for each style of use? It's not exactly cheap to swap gears until your happy.

I am wondering the same thing. I want a good gear for road courses. Given how steep 1st is though, 3.73's might not be useful. I'm going to wait to hear from people who've tracked their cars before deciding myself.

City cars would get better MPG with the 3.73. Also you see the UPGRADE price ??? Cheap as dirt.

I would go 3.73 for sure from the factory.................

I tried this calculator.

http://www.f-body.org/gears/

and using 7000 rpm and 1:32 gear and 3.73 rearend with a 235/50/18 tire i get 115mph.

3.55 gets 121mph in 4th.

different tire size might have lowered theirs. so it seems 3.55 might be better off with more hp.

How many people here have tried different gears in their 2011 GT, and can give us a real-world perspective on what might be the best gear for your driving style based on your experiences?
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Exactly. Give it some time before deciding on a gear. And even besides that, it is quite impossible to make a reasoned recommendation without knowing how the car is going to be driven/raced/etc.

There's 20 threads on this already. Search the forum.

Like has been mentioned already, it all depends what you'll be using the car for. There are advantages and compromises to each of the three gear choices. Personally I'd stick with the standard 3.31 gears, since they should be the best for autocrossing (being able to stay in 2nd gear longer) and I'd be more concerned about autocross performance than open track or 1/4 mile performance.

The 12.7 1/4 mile was with the 3:73 gears so I assume that is the fastest axle

No.


This is in regards to the C/D article that showed the 4th gear redline mph to be 110mph. The car in that issue had 3.73s and "only" trapped at 109mph. My thinking was maybe it was too much gear when coupled with the new transmission gears for the best 1/4 times (which was my original intent to ask - should have clarified that), if it is already that far maxed out with the mods that pretty much everybody here will add at some point. I tried the calculators as well and it is around 115mph so perhaps they made an error. They are also showing redline to be 6900rpm not 7000rpm as I though it would be.


Also, for everybody that instantly goes to the USE THE SEARCH BUTTON! card, there would be about 3 threads on this site, about who has the best tune and CAI kit, how much hp does a $1000 set of headers add, and what gears are the best for my car. Kind of defeats the purpose of the forum - an open sharing and exchanging of ideas, questions, and information. :catfight:

Isn't the 1/4 mile time much more important than the trap speed anyway?

:offtopic:







:topic: If everybody would search the forums on this 2010 + Mustang thread, they're wouldn't be anybody posting anything anymore since everything has been said on this 5.0 so far. So let's give this poster a chance to ask something that's legit for him to know. Some other posters may come up with new ideas and answers.

Time is the most important, but the trap speed can sometimes be indicative of certain factors.. A high trap speed but poor time might indicate that the car may be capable of better times. A trap speed that's right at the maximum speed for a given gear might indicate it's wasting time revved against the limiter instead of accelerating, which could mean either a change in quarter mile strategy or, as some are considering, that maybe the 3.73 gears are overkill and that the 3.55s would yield better times since the car could accelerate another 5 MPH without shifting up.

But point is, analyzing the different areas of the run may help deduce how to get the best time overall.

Again, grain of salt with this, I'm book learned on drag strips here.

Maybe no one uses the 10% rule anymore.

Use this:

Maximum Speed = (rpm X 60) ÷ (Gear Ratio X Tire Revolutions Per Mile)

10% Rule = 10% more RPM through traps and adjust with tire size or raise the rev limiter.

If you are pulling hard through the lights - too little gear. If you are shifting at 1188 ft to 1320 ft, too much gear.

So I ran the calc.

With a 6900 redline and 3.73 gear +.32 = 4.05 (for the difference between 4th and 5th gear since the calc is 1:1) and the Brembo package revs per mile of 769.5 (255/40/19)

I get 132 mph and at 109 mph they are at 5697 rpm through the traps.

But my math may be off.

Even if they were hitting the rev limiter in the traps, it would have virtually no affect at all on the ET. A little on the MPH, but not much, as the car's redline is only a few hundred rpm above peak HP.

For optimum acceleration with a street-style tranny, it is typically necessary to shift several hundred rpm (like...800...ballpark) above peak to maximize HP in each gear. Then run through the traps AT LEAST that high, if not higher. The last 100 ft of the 1/4 mile is almost inconsequencial to ET. Next time you go to the track....try it. Your MPH will nose dive....your ET will be virtually unaffected.

Your numbers are off. With a 27" tire, 3.73 gears, and a 1.32 4th gear, 6900 rpm nets 113 mph.

Edit: Easy to use calculator: http://www.camaroz28.com/calcs/rpmmph.html

Looking at max speed in 4th I would go with the 3.55 gears. Would probably give you the best trap speed at near stock power levels. What would 3.55's make 4th gear max at?....close to 120 I would guess, Depends what you want to do with the car.

The camaro has a similar problem...it maxes out in 3rd gear at 110. 4.10's would be the best gear for the camaro. I think that would bring 4th gear down to the mid 120's. Not to mention it would get the heavy car moving.

Based solely off what we know so far....and for drag racing....with a stock GT....3.55s will leave the car undergeared. At 112 mph, it would only be turning ~6500 rpm, or ~100 rpm short of peak HP. In drag racing, I want to several hundred rpm OVER peak HP rpm in the traps, and most certainly not under it.

I'd likely opt for the factory 3.73s. With bolt-on modifications, I'd do the same, as the first thing I'd do is move the factory rev limiter UP about 500 rpm, and tire down to a 26" DR.

Now, if 5th gear can be powershifted (not possible with a T5, T45, T56, 3650, or 6060), that opens up a whole new set of options. However, this remains to be seen, and would need to be tested.