How do I know which speedometer gear to use?
What gears should I get?
- Count the teeth on the speedometer drive gear.
- Find the gear ratio for the drive axle.
- Calculate tire revolutions per mile.
- Calculate the required tooth count for the driven gear.
- Get the Driven Gear (for your transmission) with the closest tooth count to your calculations.
Where is the speedometer drive gear mounted?
The speedometer cable gear (driven gear) is mounted within a sleeve/housing that goes into the side of the transmission’s tailshaft housing. This is where the speedometer cable attaches to the transmission. The driven gear’s teeth contact another gear (drive gear) that is attached to the transmission’s output shaft.
How do I recalibrate my speedometer?
Press and hold the calibration button located on the speedometer, start the vehicle, and then release the button. Press that button again and then take the test drive. Once you have driven the distance needed, press the button once more and the speedometer will calibrate itself to accommodate the new tire size.
What does the driver gear do?
The gear that supplies the energy is called the DRIVING GEAR (often called the driver). The gear to which the force is directed is called the DRIVEN GEAR (often called the follower). Look at the gears above. A large gear (X) driving a smaller gear (Y) decreases torque and increases speed in the driven gear.
What does a gear shift lever do?
The gear shifter allows the vehicle to be put into different gears on a manual transmission. In an automatic transmission, the gear shifter is known as a gear selector. The gear shifter is normally located between the two front seats of the vehicle on a manual transmission.
How much does speedometer change with bigger tires?
You might ask: do bigger tires make your speedometer faster? The answer is no. Tire size and speedometer accuracy are directly linked to each other. Up-sizing, or installing a taller tire, will lead to a speedometer reading that is slower than your actual speed.
How do you adjust the speedometer after bigger tires?
What gears increase speed?
Gear reducers with spur gears are used for increasing speed.
How do you know what gear to drive?
The gear attached to the motor shaft is considered the first gear, or the “drive gear”, and the other gear, whose teeth are meshed with the drive gear, is considered the second gear, or “driven gear.” Count the number of teeth on the drive gear and on the driven gear.
What causes speedometer to be off?
The most common causes of a speedometer that stopped working include are a faulty speed sensor, a broken gear on the speedometer, damaged wiring, or a faulty engine control unit.
Why is my speedometer wrong?
Reasons why your speedometer is inaccurate Damaged wiring or a blown fuse could be enough to through the speedometer out of whack. A malfunctioning sensor or engine control unit could be reporting an erroneous speed. A change in wheel or tire size could even throw off the senor and its calculations.
What is the gear ratio of a Muncie M21?
2.20:1 ratio
The 2.20:1 ratio first gear is usually referred to as the Muncie M21 transmission; based on GM’s production codes.
How many splines does a M21 have?
21.
| Input Shaft Identification | ||
|---|---|---|
| Years | Type | Output Shaft Splines |
| 1970-’74 | M20 | 32 |
| 1963-’70 | M21 | 27 |
| 1970-’74 | M21 | 32 |
How far off is my speedometer with bigger tires?
What is the difference between M20 and M21 gearbox?
Getting back to the HQ type M20 (6cyl & 253 V8 only) its 1st gear ratio is 3.07, the M21 (308 & 253 only) has a 1st gear ratio of 2.54. The M22 (6cyl One Tonners only) has a 1st gear ratio of 3.74. These boxes carry thru to the VK Commodre (M22 finished with the WB One Tonner).
What is the difference between Muncie M22 and M21?
The M22 to come later in 1967-’74 is also a close-ratio unit, but much stronger than the M21, with a higher torque capacity. Because the Muncie has so much in common with the T-10 and even similar Saginaw boxes, it is easy to get this guy mixed up with non-Muncie units.
How strong is a M21 gearbox?
With the standard 3.36:1 differential ratio, the M21 gearbox gave them maximum speeds in each gear of 50, 75, 100, and 125 mph. The taller 3.08:1 ratio differential raised the speeds in each gear by about 10% and increased the top speed to 135 mph.” This is why most guys were after M21’s when I was racing.
Do bigger tires make odometer faster?
Bigger tires affect the odometer as larger tires naturally travel greater distances with every revolution made by the tire. However, that is only when you recalibrate the odometer to account for a tire size change. If you don’t recalibrate the odometer, bigger tires won’t affect it.
Do bigger tires make your speedometer faster or slower?
Up-sizing, or installing a taller tire, will lead to a speedometer reading that is slower than your actual speed. This is because a taller tire will have a larger overall circumference, causing it to need to travel more distance per revolution than the original equipment tire.
Do bigger tires affect gear ratio?
When changing gears for taller tires, you are heading to a numerically higher gear ratio. The higher the gear ratio, the smaller the pinion gear.
What’s the difference between an M21 and an M22 Muncie 4 speed?
The M20 and M21 transmissions produced from 1963-’74 are easy to identify in both wide- and close-ratio units. The M22 to come later in 1967-’74 is also a close-ratio unit, but much stronger than the M21, with a higher torque capacity.
What is the difference between a Muncie M20 and M21 transmission?
GM’s goal with the Muncie four-speed was to produce a better shift employing larger synchro cones. He tells us both the M20 wide-ratio and M21 close-ratio transmissions were first offered in 1963….Guide to Muncie M20, M21, and M22 Four-Speed Transmissions.
| Muncie Four-Speed Gear Ratios | |
|---|---|
| M20 Wide-Ratio 1963-’65 | |
| Reverse Gear | 3.11:1 |
| M21 Close-Ratio | |
| First Gear | 2.20:1 |
What’s the difference between a M20 and an M21 gearbox?
How far off will my speedometer with bigger tires?
How do you calibrate a speedometer after changing gear ratio?