It's not your typical seventh gear. Far from it.
One look at the top of the manual gearshift knob in the new 2021 Ford Bronco reveals something quite interesting. There's a 'C' directly beneath the 'R' (reverse). This crawler gear is not exactly a typical seventh gear. Instead, it allows manual-equipped Broncos to literally crawl through rough and rocky terrain with on-demand torque. But the true purpose of the ultra-low crawler gear is really about giving the driver precise throttle control at low speeds rather than putting down tons of power to the wheels.
Engineering Explained has just released an extremely interesting but mathematically complicated video explaining just how impressive the crawler gear is. The video includes Jason Fenske's typical whiteboard filled with a lot of calculations and graphs. It could be a bit complicated for those who are mathematically-challenged.
There's no shame in that because this is very complex, but here's basically what Fenske is saying:
The Bronco's manual transmission crawler gear has a ratio of 6.588 to 1. To compare, the first gear's ratio is 4.283 to 1. This means the crawler gear isn't meant for high speeds. And then there's the matter of torque, but rather wheel torque and not engine torque. With the transfer case in low range, the SUV can produce a crazy 29,372 lb-ft of maximum torque, but it's not physically capable of managing that. You see, wheel torque is not a good indicator of a vehicle's performance due to wheel slippage and the vehicle's total weight.
EV automakers, including Tesla, love to talk about wheel torque produced by electric motors because the numbers are obviously very high and indicate amazing performance. But Fenske's whole point is that wheel torque can't be completely utilized, but it can be smartly maintained so that it doesn't burn out your clutch when doing things like rock crawling. The crawler gear is all about making the Bronco manageable when traveling up to 5 mph or so. Riding the clutch is not necessary.
Of course, if you want a far more detailed explanation full of complicated math and formulas, check out the entire video.