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Discussion Starter #1
My car curently has the factory 3.82 gear set. I know that Ford Racing offers a 4.06 gear. I have installed the FRII camshafts and the car really needs more gear to take advantage of the new power higher in the RPM's.

Are there any other ratios available? if so where or what other Ford application?

Who has installed a different gear ratio and what were your driving impressions?

Thanks!
 

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Try a shorter tire.Swapping gears is a pain and the small difference between 3.82's and 4.06's really isn't worth the effort.A 1" shorter tire will give you the same results much easier and cheaper.
 

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Yes, it's a cheap mod, but then your speedometer will not show your true speed. [thumbd]
I have not seen another ration available out there but I have not search either.
Happy moddin' [thumb]
 

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I've found very little difference on the speedo with the 4.06 gears installed, verified by a GPS module. My speedo is always either dead on or a half mile per hour off with stock size (205/50 16s) tires installed.

As far as little difference between 3.82 and 4.06...have you ever driven a Focus with the 4.06 gears installed? It was the first major mod (along with aluminum flywheel and LSD) that I did to my car, and even when I still had the stock header and catalytic converter installed it really woke the car up. Its a great mod if you're staying N/A, but its too short for FI applications.

You can get a 3.41 ratio gearset, but that's moving in the opposite direction (longer gears,) which would be ideal for FI applications. I recall having heard there was a 4.25 or higher ratio, but that would be incredibly short and not street-friendly at all.

Installation isn't supposed to be that hard, but if you're not experienced with working on a transmission I wouldn't suggest it. It'd be cheaper to pay someone to put the gears in for you than to take them the gearbox and a box of disconnected parts and tell them to put it back together again.
 

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First you tell me it's so close it desn't affect your speedo and then you tell me your car is SOOO much faster with an insignificant final drive ratio change.Make up your mind.Installation of a ring and pinion IS difficult.Changing tires isn't.A GPS module?I suppose you are one of those guys with three tachs on the dash too.
 

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^
OK [:)][:)][:)][:)][:)][:)][:)][:)], the GPS module is a USB unit that plugs into my laptop and works with the atlas program I have for work, which also displays realtime MPH. But that's not possible, if I have anything with GPS in my car that means I'm ricing it out with "three tachs on the dash", right?[rolleyes] GPS is known to be the most accurate method for measuring speed, so either the final drive ratio change has little effect on the speedometer or I'm a lying sack of shit.

I never said it was easy, nor did I say it was that hard. It all depends on your level of experience. Like I said, if you don't have much/any experience working on transmissions you're better off leaving it to the pros. There are people on this forum who have done their own drive gear and differential installs...I left it to the pros, but its not out of the question for someone who isn't a certified mechanic to do.

I'll ask again, have you ever driven a Focus equipped with 4.06 gears? If not then don't tell me what driving one is like.
 

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i once just bought the LSD and gears installed in a spare tranny but then had to resell them :( i dont remember hearing anything about the speedo being thrown off w/ the gear change
 

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i haven't driven a Focus with 4.06's,or 3.55's,or 4.11's,or 4.56's or 488's or 5.13's and so on.BUT,I have installed HUNDREDS of new gears in cars.HUNDREDS.Then driven them afterwards and have had to explain to owners that their car is now slower 0-100. I have attempted to talk people out of INSIGNIFICANT ratio changes because some dipwad told them it would make their car SOOOOO much faster,or better(?).It's not worth the hundreds of dollars.Let the guy try a set of shorter tires and see if he feels the change is worth making permanent with a gear change.Sometimes changing ratios makes the car slower.Plug that into your laptop.
 

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Discussion Starter #10
This is some really good tech info here guys, thanks... :Rollseyes:

This isn’t my first time around the block with a gear swap on a vehicle, however it is my first time dealing with a Focus.

The only way a gear swap wouldn’t affect the speedo would be if the speedo gets its signal from a speed sensor on the wheel or axle some how. In my vast experience with Mustangs, the signal comes from a speed sensor in the transmission. I don’t care if you change a 4.10 - to a 4.30 in a Mustang (for a net change of .20) you WILL see a speedo calibration change that will have to be addressed in the computer 99-up or speedo gearing 98-back. The change in 3.82 to a 4.06 (net change of only .24) is minor, but that seems to be the only choice available.

My experience tells me that my car WILL benefit from a final drive change to a lower gear ration (higher numerically). If a 4.06 is all that is readily available, then that’s what I’ll use.

I need to pull the transmission to install a clutch, so while I’m there I may was well add the gear and possibly a LSD.

breakaway, If I had access to a set of wheels and tires that would exactly duplicate a swap from a 3.82 to 4.06, you might have a valid point. However, as much as this may seem feasible to you, where am I going to come up with two oddball tires to test this theory? I am certainly not going to buy tires or wheels to test this.

Can we please get this thread back on track with REAL technical information?

I assume that I can recalibrate the speedo with another custom tune. Is this correct?
 

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Yes, you can adjust the gear ratio in the tune. I was looking at that the other day in my XCal2.
 

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I have the 4.06 in my car.......I love it, only thing is, it makes a "interstate run" a lil harder to do, because you have to bring yourself to a lower speed to take advantage of the zetecs torque when running somebody at a roll......but in a straight line or a drag race it helps alot in my opinion
 

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For road racing I would like the 4.06s as well, with or without FI. Having just that little extra coming out of a corner can make all the difference.
 

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Gear ratios and top speed

I have a quick question on this subject,

will the 4.06's positively or negatively affect my overall top speed?
 

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If you can pull redline already with the stock gearset ,4.06's will reduce your top speed.(assuming you do not raise your redline)
 

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I recall someone did the math on here once, and the 4.06 gearset only knocks ~9 MPH off of the technical top speed. Now maybe its just me, but somehow I doubt that many people on here (or people with Foci period) routinely run their car up to or past 140, given that without extensive mods a Focus can only do about 120 on a flat road and maybe 130 going downhill with a tailwind. I'll gladly trade a few MPH at the very top of what the car is capable of (espeically since I don't even have my speed limiter turned off and can only hit 108) in exchange for faster acceleration at the bottom.
 

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You shouldn't see a change in your speedo calibration, as I seem to recall the speed sensor being driven at the output end of the transaxle. That would put it after the final drive gears, and thus give you a true reading. Unlike a Mustang, or most other front engine/rear drive cars where the sensor is on the tail end of the transmission, which doesn't contain the final drive. I'm going off of memory here, though, so don't hold me to that.
 

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actually, the 4.06 does require a recalibration. the VSS sensor takes a reading off a trigger wheel on the differential. changing the gears changes the distance the tires roll per diff revolution, but the VSS will only still see one revolution. you'll end up throwing a vehicle speed mismatch code because the vss input won't match the abs sensor inputs
 
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