gears

[TheSean]

i know this is a technical post, but noone ever reads that forum.


this chick i know bought a mustang GT, and i went to inspect it for her. well.. it has a K&n and had a manifold-back xpipe/exhaust with flowmasters (i think) and turndowns under the car. the dealer (orlando infinity) doesnt know their ass from their elbow about those cars, so she got a great deal and they thought it was stock. Anyhow, after she bought it i was driving it and figured out she had gears. the speedo was off, but i attributed it to the CEL being on because there were no cats. I think they are 3.73s because they just dont pull like the 4.10 cars ive been in, but is there a way to figure out what ones without opening the pumpkin and counting?

Maybe one of you mustang guys can drive it when she comes back to daytona. She wants me to drag race it for her (i had to show her how to burnout the other day and she sucks at driving) and i want to know how to launch on street tires with those gears.

She said it's 10mph over what she is actually going, so maybe that can help dignose it. Also, any idea what that car can run with a decent launch? Thanks,



Sean

[maximumvelocity]

hey sean, get under the car and count how many time the driveshaft turns for every time the rear wheels make one rotation. That will get you the gear ratio. don't know if you can trust the tach to be on.

[TheSean]

so it's like ... 3.73 turns of the DS for every turn of the wheels? how the heck am i supposed to differentiate that from 3.5(?) or 4.10 turns? i thought maybe someone would know because the stangs have to get some correction programmed for the speedo when they change gears, right?

[HORSEpower]

What year mustang is it. 95 and older stangs don't have electronically recalibratable speedos. 93s have a mechanical speedo. The only real way to figure out what kind of gears it has is to put it on a dyno or take the back cover off the diff and count the teeth. To fix the speedo, you just have to get the correct speedo gear for it. You could also pull the speedo gear out and count the teeth. Then you will be able to figure it out from that, but it will be tougher.

Kurt

[maximumvelocity]

sean, just use chalk or a crayon or even a pencil mark on the drive shaft yolk, then one non movable part such as the edge of the pumkin. right next to the yolk. you can get a damn good estimation of what you have under there. If you can't destinguish between half a turn and three quarters of a turn then you've got some problems. you should be able to tell apart a 3.5 forma 3.73 and a 4.10 is what at least a quarter of a turn more than a 3.73 right? Not that difficult... :blah:

[HORSEpower]

If the car is a stick, you can drive beside it on the highway. With 3.55:1 gears, the car will go exactly 92 mph at 3000 rpms in 5th gear. With 3.55:1 gears, in 4th gear, the rpm/mph ratio is app. (depending on tire height) 48:1.

Kurt

[maximumvelocity]

thats taking into account that the tachometer is correct.

[HORSEpower]

93 and older stang tachometers drop off a little up top. They read about 400 low up top. In the 3000 rpms they are accurate. 94 and newer stangs are DOB accurate.

Kurt

[TheSean]

its an 01


at 80mph it says 70.

[thickstunalexndr]

How about when she gets into town, I'll plug my tuner into her car and correct for 3.73. Then we can drive down the road with another car and see if the speedometers match.

I can't leave the setting on her car...but she'll at least know if she has 3.55's, 3.73's, or 3.90's.

[HORSEpower]

OK, are you sure that it is 10 mph off, and what does the tach read?

Kurt

[Ponyperformance6]

Sean, I can figure it out for her no problem. I think I should be able to feel it, if it is 4.10s there will be a huge bottom end difference from my car, and 3.73s will be a lot closer. Besides that, I also have a tuner for her that can adjust her speedo calibration and run diagnostics to see if it is that causing her speedo to be off or what. Most likely it is, and she will need either a tuner or a speed calibration box to fix it. www.dallasmustang.com sells a good speed cal box, and they also sll MIL eliminators to get rid of that pesky check engine light. Lemme know when she comes into town and we'll figure out the gear situation.
Will

[Ponyperformance6]

01s dont have speedo gears to change in order to recalibrate, they are all digital. I dealt with it on the 98, its not that big of a deal, and my tuner can figure out really easily what gears she has, it shouldn't be a problem. It would definately be something good for her to know, even better is she can find a reciept showing who put them in and stuff.

Sean, it is a manual tranny right ??

[TheSean]

5speed.

she lives in clearwater, but will be around sometime. will any of these "tuners" you guys speak of permanently calibrate the instrumentation, or is it just to check it? in other words, can the computer be reprogrammed to think its got diff gears, or does she need to buy and permanently install something? thx.


Sean

[Ed]

They should reprogram it permanently...but if they work anything like the LS1 tuners, it needs to be the same VIN. Not sure if it's different with the Mustangs or not.

[Ponyperformance6]

No they won't reprogram it permanantly, just because If I use it to program her car, then I can never use it on mine or anyone elses car again. Superchips does it that way so no one buys a tuner and then gives it to 20 of their friends. Once you use it on one car, the tuner becomes VIN locked so it doesnt work on any other car. She can buy one of these though, and you can hardwire it in to her electrical on a switched and fused 12v source (like the cigarette lighter) and it will work fine.

http://www.dallasmustang.com/index.mvc?Session_ID=dfe1c0ad46e639dc4d950eb89faa4 3a6&Screen=PROD&Product_Code=9910T&Category_Code=L _Drivetrain_SpeedometerAccessories

Will

[HORSEpower]

Or, if you know what gear you have, you can just change the $6 gear on the end.

Kurt

[Ponyperformance6]

To my knowledge there isn't one in 96 and up Mustangs. I know it may sounds wierd, but I have been told that by several people.


Will

[HORSEpower]

There is a speedo gear on the picture in the link.

Kurt

[Ponyperformance6]

ahh I stand corrected sir