What is the gear ratio of the Astro van AWD?
The Astro van AWD does not have a single fixed gear ratio. The ratio varies by model year and configuration, with common rear axle ratios around 3.42:1, 3.73:1, or 4.10:1, and a transfer-case low-range around 2.6:1. Check your specific vehicle to confirm the exact numbers.
In practice, the Astro AWD uses a front differential, a transfer case, and a rear axle. The overall gearing a driver experiences in AWD depends on both the rear-axle ratio and the transfer-case low range. Different production years and options produced slightly different combinations, so owners should verify their exact setup rather than assuming a single figure.
Drivetrain architecture of the Astro AWD
GM’s Astro vans built in the 1990s and early 2000s offered an all-wheel-drive configuration that paired a front differential with a transfer case and a standard rear axle. The high-range in the transfer case is typically 1:1, while the low-range provides additional crawl gearing. The precise figures depend on the factory axle and transfer-case pairing for a given vehicle.
Key components that influence gearing
- Front differential: helps distribute power to the front wheels in AWD mode.
- Transfer case: provides a low-range gear (for off-road or challenging roads) and a high-range 1:1.
- Rear axle: the primary contributor to the vehicle’s final-drive ratio; the most commonly seen rear-axle ratios on Astro AWD models are in the 3.4x to 4.1x range, depending on the year and option package.
Common axle gear ratios
Before listing the typical rear-axle sizes found on Astro AWD vans, note that exact numbers vary by production year and trim. The following ratios are commonly cited in maintenance manuals and owner discussions for this vehicle family.
- 3.42:1
- 3.73:1
- 4.10:1
These rear-axle ratios determine the final drive along with the transfer-case gear when the vehicle is in AWD. The availability of each ratio depends on the specific build sheet for the vehicle, so not every Astro AWD will have all three options.
How to verify your van's exact gearing
To confirm your van’s precise gear ratios, use a combination of documented sources and physical checks. The steps below guide you through identifying the exact numbers for your specific vehicle.
- Locate the axle ratio information on the vehicle’s identification labels. Check the driver’s door jamb sticker or the glove box build sheet for an “Axle” or “Axle ratio” code.
- If the sticker doesn’t show the ratio, consult the vehicle’s VIN-derived build sheet or a GM service/parts database for your exact model year and trim.
- Inspect the differential tag on the rear axle (the tag or stamping may list the ring gear tooth count or the axle ratio).
- If necessary, physically count the teeth on the ring gear and pinion to calculate the ratio (note this requires removing the differential cover and is best done by a qualified technician).
- Cross-check with a service manual or repair guide for your year/model, as some configurations may differ by production run or regional market.
Understanding the exact gearing is important for maintenance, tire choices, and drivetrain diagnostics. When in doubt, a certified mechanic or GM dealership can provide a definitive answer using the vehicle’s VIN and a service bulletin database.
Summary
In short, there isn’t a single gear ratio for the Astro van AWD. The final-drive depends on the rear axle and the transfer-case configuration, with common rear-axle ratios ranging roughly from 3.42:1 to 4.10:1 and a transfer-case low-range around 2.6:1. To know your exact numbers, check the door jamb sticker, consult the build sheet or VIN-decoding resources, and if needed, inspect the differential tag or consult a GM service manual.
How do you tell if you have 3.73 or 4.10 gears?
You can tell if you have 3.73 or 4.10 gears by manually counting, checking the differential cover for a tag, or finding the ratio stamped on the ring gear. The most direct method is to lift the rear wheels, rotate one tire one full revolution, and count how many times the driveshaft turns; 3.75 turns indicates 3.73 gears, while slightly over 4 turns indicates 4.10 gears.
This video demonstrates how to check your gear ratio by counting the driveshaft turns: 48sBent Motorsports OffroadYouTube · Sep 22, 2023
Method 1: Manual count (with the vehicle jacked up)
- Jack up the vehicle: Safely lift the rear of your vehicle and secure it on jack stands. Ensure the wheels are off the ground.
- Mark the driveshaft and a tire: Place a mark on one of the rear tires and a corresponding mark on the driveshaft.
- Rotate the tire: Rotate the marked tire forward one full revolution. For an open differential, you may need to lift only one wheel and have someone hold the other stationary, or lift both wheels and rotate one tire twice while the other tire is on the ground. For a locked differential, lift both rear wheels and have one tire rotate once while the other rotates once in the opposite direction.
- Count the driveshaft turns: Count how many times the mark on the driveshaft has rotated.
- 3.73 gears: The driveshaft will turn approximately 3.753.753.75 times for one full tire revolution.
- 4.10 gears: The driveshaft will turn a little over 444 times for one full tire revolution.
Method 2: Check the differential cover tag
- Locate the tag: Look for a small metal tag that is usually bolted to the differential cover. It may be on one of the bolts.
- Read the ratio: If the tag is still present, the gear ratio will be stamped on it. It will likely be a number like "3.73" or "4.10".
You can watch this video to learn how to find the differential cover tag: 51sFlawed OffroadYouTube · Apr 18, 2022
Method 3: Read the ring gear stamps
- Locate the ring gear: This requires removing the differential cover to get a clear view of the ring gear.
- Find the numbers: Look for two numbers stamped on the teeth of the ring gear, such as "41" and "11".
- Divide the numbers: Divide the larger number (teeth on the ring gear) by the smaller number (teeth on the pinion gear).
- 41÷11≈3.7341 divided by 11 is approximately equal to 3.7341÷11≈3.73
- 41÷10=4.1041 divided by 10 equals 4.1041÷10=4.10
This video shows how to read the ring gear stamps to find the gear ratio: 46sJL LIFE OFFROADYouTube · Nov 18, 2022
How does Astro Van AWD work?
Once the front and rear wheel speed varies the unit transfers torque in proportion to the speed. Differential. In other words the wheels that have the traction get the power.
What is a 3.73 gear ratio good for?
A 3.73 gear ratio is a good all-around choice for improving a vehicle's acceleration and towing performance without sacrificing too much highway drivability. It's considered a balance between gears focused on maximum fuel economy (lower numbers, like 3.55) and gears optimized purely for quick acceleration (higher numbers, like 4.10).
What a 3.73 gear ratio is good for
- Better acceleration: It provides more torque to the wheels, resulting in quicker off-the-line performance and a more responsive feel.
- Improved towing: The extra torque makes it easier to tow heavier loads, as the engine doesn't have to work as hard.
- Compensation for larger tires: It can help a vehicle with larger tires regain lost performance and acceleration.
- Good for street/strip use: It offers a good compromise for performance applications like street trucks or drag strip use.
What a 3.73 gear ratio sacrifices
- Fuel economy: The engine will have to spin at a higher RPM to maintain the same speed as a vehicle with lower gears, which can reduce fuel efficiency.
- Top-end speed: It can result in a lower top-end speed compared to higher gears because the engine will reach its redline at a lower vehicle speed.
How it compares to other ratios
- vs. 3.55: A 3.73 ratio offers better acceleration and towing than a 3.55. A 3.55 is generally better for highway cruising and fuel economy.
- vs. 4.10: A 4.10 ratio provides even quicker acceleration and more torque but at the cost of higher RPMs at highway speeds and reduced fuel economy. A 3.73 is often preferred for better highway comfort.
What is the gear ratio of a 2000 Chevy Astro van?
3.73
Gear ratio 3.73. With 7.5 Ring Gear.
