Among many of the jaw dropping features announced during the Bronco reveal, one that stood out to hardcore off-roaders was the ultra-low crawler gear.
Although the manual is listed as a 7-speed, it is different than what you may think. Typically the higher gears on manual transmissions are for lower cruising speed RPMs, greater top speeds and better fuel economy—so how does this benefit the Bronco in an off-road situation?
What is a crawler gear?
As you can see from the Bronco’s shift knob, there is a C (crawler gear) and 1-6 gears.
It is more of a 6 speed + crawler gear than an actual 7 speed manual. The "C" acts as an ultra low first gear.
Lets get technical
A crawl ratio of 94.7:1 means that for every 94.7 engine rotations, your wheel rotates once. For comparison, the Bronco’s first gear has a gear ratio of 4.2:1 which means that for every 4.2 engine rotations, the wheel rotates once. The crawler gear provides greater engine power per wheel rotation.
The Bronco's 6.588:1 crawl gear ratio, paired with the shorter 3.06:1 low gear of the two-speed transfer case and the shortest 4.70:1 final drive ratio gives the crawler gear a 94.7:1 crawl ratio. Theoretically the Bronco will send 29,372 ft/lbs of torque to the wheels. You may be thinking “Almost 30,000 lb/ft of torque?! What are you gonna do with all that power on the rocky trail?!” The actual likely hood of putting that much torque to the ground depends on other factors such as vehicle weight and tire size.
OK, what does that mean for me?
The super low gearing allows you to give more accurate throttle control instead of sending too much power and spinning tires when you need grip. The ultra low gear makes so much power available that won’t have to ride the clutch at slow speeds. No more worrying about a burning or slipping clutch when you’re on a difficult obstacle. You will be able to cruise as low as 1mph with the clutch fully depressed.
More torque and better power delivery means better ability to crawl over difficult obstacles. The drivetrain combo gives the crawl gear a top speed of 7 mph in low range. Designed for off-road scenarios, you will never need C on an everyday pavement situation.
Is the automatic less capable?
When equipped with an automatic, the Bronco comes with a 10 speed transmission. The automatic transmission features a crawl ratio is 67.8:1.
Comparing the numbers, remember that the manual Bronco has a crawl ratio of 94.7:1. The Wrangler Rubicon has a crawl ratio of 84.2:1. The numbers might sound less competitive but the automatic transmissions torque converter also aids in power delivery along with help from the brakes. Trucks with a crawl ratio greater than 50:1 are considered to be pretty capable. Especially when paired with the front and rear locking differential, you shouldn’t have a problem crawling in the Bronco, regardless of which transmission you choose.
Is this exclusive to the Bronco?
No. This was a common feature in utilitarian trucks in the early to mid 1900’s. Sometimes called a “Granny Gear,” this super low ratio first gear was used as recently as the early 90’s in the 1991 Chevy Blazer with the SM465 transmission. You can also regear your transmission and transfer case with lower aftermarket gears to create an ultra low crawl ratio.