do I have 3:73 gears?
- Thread starter jake_1977_77
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ninety15.0
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- Mar 10, 2004
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This is what you do. Put the rear of the car on jackstands. Take a white crayon or piece of tape and mark the tire at one location and the dirveshaft at one location. This may take more than one person but turn the tire exactly one full revolution. Count the number of revolutions that the drive shaft makes during the single tire revolution. If you do have 3.73's then you will see the driveshaft turn 3 and 3/4 times for every 1 revolution of the tire. Simple and quick
ShortThrow50
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Ha. You could always get out on the road and when your in fourth gear youll notice how high your rpms are at cruuising speed.
ninety15.0
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- Mar 10, 2004
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This method is not nearly as accurate b/c tire size and tranny ratios may not all be stock. Check the ratio as i described above...its the most quick and accurate way.
I would have to agree with you, thanks, by the way I have 18" wheels not stock, will that make any difference?
ShortThrow50
Member
I wasnt trying to be a wise ass. It wouldnt hurt to pull that diff cover to change your fluid either. When you do this, more than likely the gear ratio will be stamped on your ring gear.
...unless the tires mounted on those 18" wheels don't have the same total outer diameter as the stock-sized tires, or the speedo gear was never swapped out for a proper number-of-teeth gear to go with the rear gear ratio.
The highway method could work for a so-so guesstimate, but you'd have to have the help of another driver with a walkie-talkie and another car that you KNOW has an accurate speedo. Get on the highway, have them set the cruise control at whatever specified speed (at least 55 MPH, probably better at 70 MPH), and then match their speed. Radio to them when you're set and cruising in 5th gear, and then record what your RPM's are, and what speed you're both going. Then, consult a chart (it's been posted a couple of times recently in prior posts) showing RPM's, MPH, and gear ratio. I won't say this is more accurate than any other method, but it's just another way of doing it - my buddies and I used this method while we were driving to the WFC9 last year, comparing Pat's and Jason's notches' speedo accuracy against Rob's bone-stock (at the time) '04 Mach 1.
Of course, this only works if you're running a stock-geared tranny (AOD or T-5). If you're running with a T-5 with some freaky internals, or a 4-banger T-5, then you're probably just better off with the first method of counting driveshaft revolutions per tire rotation.
The highway method could work for a so-so guesstimate, but you'd have to have the help of another driver with a walkie-talkie and another car that you KNOW has an accurate speedo. Get on the highway, have them set the cruise control at whatever specified speed (at least 55 MPH, probably better at 70 MPH), and then match their speed. Radio to them when you're set and cruising in 5th gear, and then record what your RPM's are, and what speed you're both going. Then, consult a chart (it's been posted a couple of times recently in prior posts) showing RPM's, MPH, and gear ratio. I won't say this is more accurate than any other method, but it's just another way of doing it - my buddies and I used this method while we were driving to the WFC9 last year, comparing Pat's and Jason's notches' speedo accuracy against Rob's bone-stock (at the time) '04 Mach 1.
Of course, this only works if you're running a stock-geared tranny (AOD or T-5). If you're running with a T-5 with some freaky internals, or a 4-banger T-5, then you're probably just better off with the first method of counting driveshaft revolutions per tire rotation.
IS the speedo accurate? Pull the speedo gear and count the teeth. You shoiuld have a white 23-tooth in there for 3.73's in a 1992
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