A truck’s drivetrain is the system that transmits power from the engine to the wheels, enabling the vehicle to move. Here are the main components of my drivetrain.
- Engine: The power source that generates the mechanical energy needed to drive the truck. It burns fuel to produce rotational force (torque).
- Transmission: This component adjusts the engine’s power and torque to suit driving conditions. It can be manual (with a clutch) or automatic, allowing the driver to shift gears and control speed and power delivery.
- Clutch (in manual transmissions): Connects and disconnects the engine from the transmission, allowing the driver to shift gears smoothly by temporarily interrupting power flow.
- Driveshaft (or Propeller Shaft): A long tube that transfers rotational power from the transmission (or transfer case in 4WD/AWD trucks) to the differential. Larger trucks may consist of multiple sections with universal joints.
- Differential: A gear arrangement that splits the torque between the wheels, allowing them to rotate at different speeds (especially when turning). It’s located in the axle assembly.
- Axles: These shafts connect the differential to the wheels, transmitting power and supporting the truck’s weight. Trucks often have a solid rear axle; some may have dual rear axles for heavy-duty applications.
- Transfer Case (in 4WD or AWD trucks): Distributes power from the transmission to both the front and rear axles, enabling all-wheel drive functionality.
- Universal Joints (U-Joints): Flexible joints in the driveshaft that allow it to move up and down with the suspension while still transmitting power.
- Wheels and Tires: The final point of the drivetrain, where power is applied to the ground to move the truck.
Depending on the truck’s purpose, additional components like inter-axle differentials (for tandem axle setups) or power take-off (PTO) units (for auxiliary equipment) might also be part of the drivetrain system in heavy-duty trucks.
Each component works together to convert the engine’s energy into motion, tailored to the truck’s load, terrain, and driving conditions. Let me know if you’d like a deeper dive into any of these!
My Engine:
Small Block Chevy 350 – Casting 3970010 – 1969-1980
Of course, I am going to bathe the engine. (CLICK HERE) I just haven’t gotten that far yet. Please share your best tips on cleaning the engine and engine bay in the comments below.
My Intake Manifold:
An Edelbrock Airgap intake manifold was added when the 350 was dropped into My Scout II. I reckon…. Since I wasn’t there, I am not 100% sure.
My Tranny:
727 Torque Flite 3-Speed Automatic was the original MOPAR Transmission in my 1972 Scout from what I can discern. I am prepping to have this thing rebuilt to keep me from crying when it happens.
My Shaft:
He said, “Shaft”. He he.
My Differential/Axle:
When my rear end crapped out….. You remember? Right?? I decided to grab a beefier 3:73 differential with disc brakes. 8.5 Ring Gear, USA mad castings, set 20 wheel bearings, 30 spline chromoly shafts, and stock lug pattern 5×5.5.
My Wheels:
I am sticking with the original rims here. (New Link) I am just having them painted and putting on some 33-inch BF Goodrich All-Terrain tires.
My Transfer Case:
My Universal Joints:
Speed Estimations:
My setup uses the Chrysler A727 3-speed automatic transmission, which has standard gear ratios of 2.45:1 (1st gear), 1.45:1 (2nd gear), and 1.00:1 (3rd gear). Combined with your 3.73:1 rear axle ratio and 33-inch tire diameter, I’ve calculated estimated vehicle speeds (in MPH) for a range of engine RPMs (1,000 to 6,000 in 500 RPM increments). These assume no slippage, a healthy torque converter in the A727 (which can slightly reduce effective ratios at low speeds), and standard conditions. I really want to test my GPS to see if everything looks to be in line.
The formula used is: MPH = (Engine RPM × Tire Diameter in inches) / (Transmission Ratio × Axle Ratio × 336). This accounts for tire revolutions per mile and unit conversions.
1st Gear: (2.45:1 × 3.73:1 = 9.14:1 overall)
| RPM | Speed (MPH) |
|---|---|
| 1,000 | 10.7 |
| 1,500 | 16.1 |
| 2,000 | 21.5 |
| 2,500 | 26.9 |
| 3,000 | 32.2 |
| 3,500 | 37.6 |
| 4,000 | 43.0 |
| 4,500 | 48.4 |
| 5,000 | 53.7 |
| 5,500 | 59.1 |
| 6,000 | 64.5 |
2nd Gear (1.45:1 × 3.73:1 = 5.41:1 overall)
| RPM | Speed (MPH) |
|---|---|
| 1,000 | 18.2 |
| 1,500 | 27.2 |
| 2,000 | 36.3 |
| 2,500 | 45.4 |
| 3,000 | 54.5 |
| 3,500 | 63.6 |
| 4,000 | 72.6 |
| 4,500 | 81.7 |
| 5,000 | 90.8 |
| 5,500 | 99.9 |
| 6,000 | 109.0 |
3rd Gear (1.00:1 × 3.73:1 = 3.73:1 overall)
| RPM | Speed (MPH) |
|---|---|
| 1,000 | 26.3 |
| 1,500 | 39.5 |
| 2,000 | 52.7 |
| 2,500 | 65.8 |
| 3,000 | 79.0 |
| 3,500 | 92.2 |
| 4,000 | 105.3 |
| 4,500 | 118.5 |
| 5,000 | 131.7 |
| 5,500 | 144.8 |
| 6,000 | 158.0 |
Update: (Some Videos Maybe?)