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-   -   reaching 120 mph slower? with 4:10 (http://mustangforums.com/forum/2005-2014-mustangs/698155-reaching-120-mph-slower-with-4-10-a.html)

mustang_gt808 07-15-2013 02:51 AM

reaching 120 mph slower? with 4:10
 
ok guys before i installed my 4:10s from 0-120 it seemed faster with my 3;55 gears? yesterday i opened it up from 0-120mph now with my 4:10 gears and it seamed when im passing 90 or 100mph it been slower reaching 120? i might be wrong but can anyone confirm this please. thanks guys

YoungBlood 07-15-2013 03:01 AM

you might have to shift sooner out of third, which might be slowing you down slightly?

cariacou 07-15-2013 04:18 AM

Quote:

Originally Posted by mustang_gt808 (Post 8248170)
ok guys before i installed my 4:10s from 0-120 it seemed faster with my 3;55 gears? yesterday i opened it up from 0-120mph now with my 4:10 gears and it seamed when im passing 90 or 100mph it been slower reaching 120? i might be wrong but can anyone confirm this please. thanks guys

yep.

ratio 3.55/4.10 = 115%

from 60>120+ your engine is working just as much as it used to with 3.55s when doing 60*1.15>120*1.15 = 70>140.

Nuke 07-15-2013 06:01 AM

Auto or manual?

Soldier GT 07-15-2013 07:41 AM

Just like any other mod it's going to take you a bit to get use to (especially gears). I had a buddy that ran a 08 GT full bolt ons and ran a consistent low 13's. He put a supercharger on it and 1st time at the track he ran a 13.6. Once you get use to the new gears and get the shifting down correct you'll be pulling alot harder than with the 3.55's....

Ricardo 07-15-2013 11:06 AM

Most guys I know who are serious about the 1/4th track run 4.10 and above...pretty sure there's a reason for that.

808muscle 07-15-2013 11:48 AM

Quote:

Originally Posted by Ricardo (Post 8248260)
Most guys I know who are serious about the 1/4th track run 4.10 and above...pretty sure there's a reason for that.

Yes....4.10's will get you in your power band quicker in a short quarter mile race. Many cars do 4.30, 4.45 and 4.88 but if you were doing a mile race 3.31 would be better suited for that.

MustangFirstCar 07-15-2013 02:57 PM

Well you do lose a little top end from a steeper gear ratio but you shouldn't be noticeably slower. Maybe you're just not used to the new gears yet.

adidasUNT8 07-15-2013 03:55 PM

your acceleration should not be slower. You are either losing traction and spinning or your driving skills have not adapted yet.

tremman78 07-16-2013 02:42 AM

youll get used to the new driving and love the 4:10's

YoungBlood 07-16-2013 04:33 PM

How do you feel about them besides over 120?

CPTCO 07-16-2013 04:38 PM

I got mine about the same time as the OP. I feel like my car is pulling harder past 120. It also seems like my power is more available in ALL gears. Many people will say they aren't the best for highway miles. But I just drove my car on a 900 mile road trip. Loved every minute. Passing cars easily in 5th, plus great launches.

Ricardo 07-16-2013 10:28 PM

Over 120? My car came with 3.31 and now with 4.10 has a higher top speed. People are misled into thinking 4.10s make you lose top speed but it's around here somewhere that the hp you need to top out that gear is pretty dang high. My car cannot hit redline in 5th with 4.10s so I doubt you will.

edit: some searching points to 180ish but thats a speed nobody here should ever go without an ambulance standing by

FlamingoGT 07-17-2013 07:42 PM

Quote:

Originally Posted by Ricardo (Post 8249316)
Over 120? My car came with 3.31 and now with 4.10 has a higher top speed. People are misled into thinking 4.10s make you lose top speed but it's around here somewhere that the hp you need to top out that gear is pretty dang high. My car cannot hit redline in 5th with 4.10s so I doubt you will.

Theoretical top speeds are slower with 4.10s than with 3.31s (or any other gear ratio numerically lower than 4.10). But where reality beats theory is that, as noted, these cars don't have the oomph to reach that theoretical top speed.

Where the 4.10s really shine is in the low end pull getting you up to speed sooner as well as allowing you more use of the power band.

outceltj 08-03-2013 04:12 PM

So my take on whether your slower with 410s could be true. I have had this talk with some friends and our conclusion was that you basically need more hp to get to it quicker. As was stated earlier there is s reason why people run 410s at the track. When ur car hits fourth you just need more power to keep her picking up speed

tbear853 08-03-2013 05:46 PM

Quote:

Originally Posted by mustang_gt808 (Post 8248170)
ok guys before i installed my 4:10s from 0-120 it seemed faster with my 3;55 gears? yesterday i opened it up from 0-120mph now with my 4:10 gears and it seamed when im passing 90 or 100mph it been slower reaching 120? i might be wrong but can anyone confirm this please. thanks guys

At 80-100 mph now likely you are in 4th instead of 3rd, and overall gearing is some higher than 3rd with 3.55s. .... but likely you are getting the first 60 feet quicker which is important in 1/4 mile runs. Overall, the 4.10s will increase torque multiplication through out the speed range as long as you keep her in the right transmission gear to keep the engine up in the power band .... to maximize torque multiplication .... and thus the engine will accelerate the car harder, reaching higher speeds in less time, and will likely run faster in 5th on top if pushing any air.

I recall in 1979 we had Chrysler Newports with 360 engines and 3.23 rear gears, then in 1980 we got Plymouth Gran Fury s with exact same engine in same body with same trim, but 2.94 rear gears. The '79s were faster accelerating and would run a good 5-7 mph faster on top because the '80s hit that wall of not making enough RPM when resistance reached a certain level about 120 .... where the '79s would push 125-127 .... but engine turned faster .... and the '80s got slightly better gas mileage.

Stang-aholic 08-03-2013 05:50 PM

higher gears (4.10s) = faster acceleration, lower acceleration over 60 mph.
lower gears (3.31s) = normal acceleration off the line, linear acceleration over 60.

The reason: 4.10s pull harder off the line because they keep your engine in the main power range (3k to 6k) more of the time. But at speeds above 60/70 your engine will be running much higher RPMs, but doing more work because the torque require to make the car go faster at that speed is greater with 4.10s vs 3.31s. Therefore your car is faster than stock 3.31s (stock) from 0-60/70mph, but slower from 70-120+

drewsky 08-04-2013 12:05 AM

My car never felt slower after 60mph after the 4:10 install. It felt like it pulled a little harder all the way through. Where are you getting this? Is there a math to this, I'm curious now

AK_Kayaker 08-04-2013 03:26 AM

Quote:

Originally Posted by drewsky (Post 8259728)
My car never felt slower after 60mph after the 4:10 install. It felt like it pulled a little harder all the way through. Where are you getting this? Is there a math to this, I'm curious now

I would agree with you, as the increased torque multiplication is going to give better acceleration across the entire speed range.
I think maybe this is some kind of Keynesian math, and I think we all know how good that stuff works. :icon_lolsign:
Maybe with luck Norm will step in and set things straight, till then. :icon_lurk5:

Norm Peterson 08-04-2013 09:58 AM

For a few mph immediately following the speed at which you upshift the 4.10-ratio car, the 3.55-geared car will have slightly stronger acceleration. This is because the 4.10-geared car loses more due to the taller overall gearing than it gains by dropping back to around the torque peak rpm. I haven't ever tried to determine what this might amount to or if it'd be enough to clearly notice.

Take the speed limiter away and I think I found that the 4.10's actually pull an extra mph or two on the top end (there's a fairly fussy mathematical simulation for determining real-world top speed). Basically, 4.10's put the engine closer to peak HP rpm in 5th at the high 140-ish/150 range than you would be with 3.55's. With 3.55's and a stockish 4.6L, you don't have enough power at enough revs to pull ~150 in 4th with stock tire sizes.


Norm


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