Gear Swap: AWD 08 STA V8 3:55 to ?

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Carey Frennier

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http://www.explorerforum.com/forums/showthread.php?t=220833&page=2



Above is a thread on explorerforum.com that was started awhile ago.



Has anyone on this site tried this yet?



I'm looking for more bottom end punch out of my 08. I'm thinking that this would work exceptionally well and may even improve my fuel economy being that this is a 100% city driven vehicle.



I'm thinking that a 4:10 or 4:30 would sit nicely with the 6 speed and my wants for more power.



What do you guys think?



Dingo, got any advice here?
 
Don't go above 4.10. I do a decent amount of highway miles, so I'm still at 3.55, but I have a 3.73 LS rear diff now that I can swap in when going to the track.
 
So you're thinking that I wouldn't like anything above 4:10 because of fuel economy? Would I negatively effect drivability?



I'm just looking looking for the "why." :)
 
The taller the gears the more revs you turn.

I went from 3:55s to 4:10s in the stang, at 70 MPH with the OEM gears I was right at 2100 RPMs, with the new gears at 70 MPH I am at 2500 RPM = worse miliage.
 
I know the rpms will go up if I go to a lower gear ratio. I'm sure it will thus consume more fuel at highway speeds.



I was just wondering if there were any other issues that would damage the vehicles performance or reliability.
 
More revs, more wear on the drivetrain (minimal)

Stay with what you have unless you can drop 2000 lbs and intend on racing the trac.
 
So you're saying that I won't get the gain I'm looking for by changing gear ratios? I need this vehicle to put me back in my seat a little more. I figured a 4:10 would give me that without causing anything extreme. I've had trucks with 4:10s and 4:11s. They ate fuel but they were only 4 speeds but they had more off the line, low end power than my STA and they did it with less horsepower. Actually, my F150 w/ 3:73 could do this where the STA cannot.



That's what the thread is about. I want more torque and low end power. So fuel economy and rpms on the highway are only a marginal concern to me.



Shaving 2000 lbs? Obviously impossible.
 
I remember my first truck. a 1991 Chevy 2500 Scottsdale 454 3 speed with 4:11s. It topped out at 75mph tacked out lol.



I had a 03 Silverado SS AWD that had awesome take off power but the truck was a complete waste of life. The quality was terrible and I had twice the problems I've had with this ST. From interior switches breaking to a bent drive shaft from the factory.
 
Ahh....yeah I kinda figured that.



Bill, I didn't ask if a 4:10 would shave 2000 pounds off my truck. I asked if anyone had any imput on a gear swap. I'm sorry if my question was missleading to you...



 
OK. So, I just spoke with my service department and they're telling me that this mod would cost about $1500 for each end resulting in about a $3000 cost.



So yeah....screw that.
 
I'm out of ideas. How does one get more low end torque, horsepower, throttle responce to result in more take off power? I'm not willing to shave any weight of the trac. What's on it stays on it.



I've done the exhaust (made a decent improvement)

I've done the intake (done after exhaust and noticed even more improvement epecially with throttle responce)

I've done the XcalII (ties all the mods together and with 93 octane performance, makes more of a profound difference than all the other mods combined.)



I don't want to go through the expense of a supercharger.



All I can think of is the Zabteck throttle body or maybe revising my tune more.

 
Drop her off in Dingo's laboratory, along with a blank check!:lol:



Here are some suggestions, from Dingo the Mad Sport Trac Scientist's mod list:



-Royal Purple ATF

-Royal Purple 75W140 in rear end

-Royal Purple Purple Ice coolant additive

-Stant 180 degree thermostat

-Steeda underdrive pulleys

-Granatelli 78,000V ignition coils

-Gates Racing serpentine belt

-Brisk Racing Silver plugs (one range colder)

-Zabteck Throttle Body



I'm not sure if blue hoses, blue tire dressing, and changing just about everything else possible under the hood to blue have shaved anything off his 1/4 time, but if he believes it to be so, then who am I to argue?:lol:
 
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Smaller tires will give you the same effect as a different gear ratio. I don't know what the factory tire size is on a STA, but going to a smaller size (i.e. 235 instead of a 255) or a lower profile (i.e. 255-60R16 instead of 255-70R16) will also give you the same effect as a new gearset. Let me know what the tire size you have is and I can let you know what size you will need to get the same effect as a 3.55 to 4.10 gear change.
 
Ouch. I forgot about the 20's on the STA's. The sidewall will get pretty thin on low profile tires.

Anyway, here is the rundown.



Tire Size----- Effective Ratio - - Sidewall Height

P255-50R20 - 3.55 - - - - - - - - 5.02

P255-45R20 - 3.67 - - - - - - - - 4.52

P255-40R20 - 3.80 - - - - - - - - 4.02

P255-35R20 - 3.95 - - - - - - - - 3.51

P255-30R20 - 4.10 - - - - - - - - 3.01!



And

P245-45R20 - 3.72 - - - - - - - - 4.34



Hope this helps.



P.S. Had to re-format. Apparently the website removes excess spaces!
 
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Maybe you can get Torrie to write you a tune focused on torque. I asked him if he could do a torque tune and he said that he normally writes tunes based on extracting the most HP and torque together, not one or the other. I think Doug at Bamachips had a torque tune available so I don't see why Torrie couldn't write one.



You wont be disappointed with the modified throttle body. Very noticeable throttle response and you'll barely have to step on the accelerator to get her going. Works hand in hand with your aftermarket intake. Have you considered a larger MAF?
 

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