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Discussion Starter #1
I have a couple of questions regarding my 2002 Mustang GT.

I purchased the car used, and I think it has 4.10 gears in it based on how the speedometer reads (tires are the right size). Soon, I am going to confirm which gears are in it by driving beside someone with an accurate speedometer. American Muscle has all the RPM/Speedo/Gear combinations for the various racing gears.

My first question is about gear noise I can hear through the shifter. Now, this is my first manual car and also my first Mustang GT, so I'm not sure what's normal and what's more noise than normal. Other people have driven the car and not said anything, but when I searched about 4.10 gears online I found tons of posts about people getting lots of gear noise after a professional install. Its nothing that really bothered me until I thought about it, its just a whirring (you might call it a whining) noise that occurs during acceleration from lower RPM's and deceleration when you let off the throttle but keep the car in gear. No noise during constant rpm and throttle with no acceleration. I'm just wondering what kind of noise form the shifter is normal and what isn't. If it makes a difference, I have a short shifter, but haven't taken off the boot to see what it is exactly.

Second question is regarding the drivetrain/transmission. When I let off the throttle at a lower speed (under 40?) releasing the drive train tension, but keep the car in gear there is a slight "lurch". I just wanted to make sure this is a result of my driving and that nothing is loose or set up improperly. I have just assumed this is because the engine is so powerful and torquey. I have not driven other manual cars enough to know if this is normal for all manual cars (no torque converter) and is more pronounced with this V8.

Thanks for all your help!
 

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To answer your second question, yes a little lurch is normal when you let off the gas, depending on how quick you let off the gas. Mine does the same as that's nothing to be worried about.
 

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Discussion Starter #3
Great, glad that's cleared up. The faster i let off the gas the more noticeable the lurch is.

Regarding my gears. I was also wondering if anything else could be affecting my speedometer besides the gears? Like i said the tires are the right size (265/35/18) and the gauge cluster is stock. Because of these I assumed it must be the gears, but I will check my RPM and speed when I can drive next to someone to test this.
 

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My speedo is off by 10%. Stock gears, right size tires, but I have white face gauges. It was like this when I bought it, still don't know what's wrong. Didn't wanna spend the money to fix it, so I just left it as is.

Example:
Speedo reads 50 when I'm doing 45.
 

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Discussion Starter #5
Hmm... That's interesting. I guess its possible the spring or some part got tweaked during the installation. I can't tell if my gauge cluster was ever removed or gotten into.

My speedometer is also off by more than 10% I believe. People pass me on the freeway when my speedometer reads 85-90mph.

I may have to do some more looking around the car to see if my gears are stock.
 

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Are you talking about the rear end making noise or the transmission? Regardless of what ratio the rear gears are, you shouldn't have any noise. If the gears are set up properly, they should run quiet. If they do make noise, it is usually more of a resonating "howl" that can be heard more noticably from the back seat. Also, the noise will usually change with accell/Decell/cruise due to the change in pressure on the gear teeth. It really shouldn't sound like it's coming directly from the shifter.

If the helical gears in the transmission are making noise, it would usually be described as a higher pitched "whine" and would eminate from the shifter location. A manual transmission will produce a slight amount of gear whine. When I had my shifter boot off to install my Hust shifter, I took it for a test drive. I was surprised at how much louder it was with the boot off. I would start by checking the fluid level in the trans.

To check your speedo, just hold at a steady 60mph cruise (per the speedo) on the highway and time yourself between mile markers. It should take exactly 1 minute to go 1 mile; any less and the speedo is reading slow, any more and he speedo is reading fast. Make a note of exactly how many seconds it takes to go 1 mile. While you're doing this, also make a note of the engine RPM and what gear you're in. (Fourth gear is direct and will make it much easier, but any gear will work). Post your results and we can calculate how far off the speedo is and what your gear ratio is at the same time. Just because the speedo is off, doesn't always mean the rear gears have been changed. The more steady you can keep it at 60MPH, the more accurate we can get.
 

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Discussion Starter #7
Thanks, Brian. I will check the trans fluid soon. I do not hear any noise coming from the back seat or rear end of the vehicle, at least not over the exhaust. From your description, the noise I hear is from the helical gears, and it is definitely coming from the shifter.

I will test out my Speedo soon and update the thread.

Do you think there are any other possible explanations for the speedo being off besides the gears?
 

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Our cars are basically 1/2 ton pickup drive trains hooked to a flashy body, so some driveline lash when pressing/letting up on the throttle is to be expected.

Here is my Rear Axle Gear Ratio Guesstimator, it's pretty accurate but not perfect--the greatest benefit is that you don't need to jack up the back-end, or have a pace car...
 

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Discussion Starter #9
Thanks cliff. I will use that calculator after I drive home. The only thing is...is that MPH on there the speedometer MPH or actual? I don't have a way of knowing my actual without another pace car.
 

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Thanks cliff. I will use that calculator after I drive home. The only thing is...is that MPH on there the speedometer MPH or actual? I don't have a way of knowing my actual without another pace car.
MPH actual is best (do you have access to a GPS unit), however using the speedometer reading will tell you what gears the PCM thinks are installed.

Changing the gear ratio in the tune is a preferred way to correct the speedometer for your '02. Often a friendly Ford dealer, or local tuner with one of the "freebie" tuning systems, will do this for minimal cost...
 

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Discussion Starter #11
I don't have a GPS but can easily borrow one. I will do this, and see what my gear ratio is.

I hope I can find somewhere to give me a tune for not too much $$. If not, I will probably buy an SCT from AM, upload the tune myself and then sell the tuner.
 

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I don't have a GPS but can easily borrow one. I will do this, and see what my gear ratio is.

I hope I can find somewhere to give me a tune for not too much $$. If not, I will probably buy an SCT from AM, upload the tune myself and then sell the tuner.
If you do that the tuner will not be worth anything, as it will be "married" to you car and nothing but a paperweight for anyone else.

The only way you can sell the tuner with any value to it would be to "divorce" it from your car by reloading the stock tune. This is true for any handheld, and most other tuning systems as well.
 

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Discussion Starter #13
Ah, I see. I guess I better go over my car carefully to see if there are any other mods the previous owner didn't know about that would justify spending the money on a custom tune.

Right now I know I have cold air intake (BBK no Check Engine Light), stock midpipe but aftermarket catback pipes, short shifter, and apparently gears (TBD what ratio). I am pretty sure there are no other mods hiding that the previous owner didn't know about.

Right now I am thinking the tune would be useful for the gears and CAI. Is that enough to justify spending the money on the SCT tune after some time and holding off on going to a dealer to change my gear ratio in the PCM?

Are there any specific mods I should look for that might not be obvious where a tune would be important?
 

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to check what gears are in your rear end you would jack the car up and mark both one wheel and the driveshaft for 3.27 gears you will rotate the wheel one turn for every 3.27 turns of the driveshaft for 4.10 it would be one turn of the rear wheel to 4.10 turns of the driveshaft. its the easiest way to check instead of guessing or dealing with speedos that are never 100% right good luck!
 

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Ah, I see. I guess I better go over my car carefully to see if there are any other mods the previous owner didn't know about that would justify spending the money on a custom tune.

Right now I know I have cold air intake (BBK no Check Engine Light), stock midpipe but aftermarket catback pipes, short shifter, and apparently gears (TBD what ratio). I am pretty sure there are no other mods hiding that the previous owner didn't know about.

Right now I am thinking the tune would be useful for the gears and CAI. Is that enough to justify spending the money on the SCT tune after some time and holding off on going to a dealer to change my gear ratio in the PCM?

Are there any specific mods I should look for that might not be obvious where a tune would be important?
The only mod I recommend before buying a tuner is opening up the exhaust to 2-1/2" from the manifold back.

The stock tune sucks, it has very conservative timing and runs pig-rich at WOT. I have tuned several bone stock cars, some for owners that wanted to stick with 87 octane, and never had one come back from their first spin without a ear-to-ear grin. Premium fuel tunes make them giddy...
 

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Thanks cliff. I will use that calculator after I drive home. The only thing is...is that MPH on there the speedometer MPH or actual? I don't have a way of knowing my actual without another pace car.
Just keep your speedo @ 60MPH (set the cruise control) and time your car with a stopwatch for a mile, using the milemarkers on the road. That will give us the actual speed as accurate as anything. The GPS is the easiest if you have one.
 
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