Join Date: Sep 2011
Location: Canada - National Capital Region
How Low Should You Go?
After months of searching, reading, and research I finally found a comprehensive answer to my question, “How do I determine my ideal crawl ratio---one that will serve me best for my specific vehicle and off-road driving needs?”
"A low crawl ratio is very important to a rockcrawling Jeep or in any other situation where low speed control is needed. The ability to idle over rough terrain at a quarter mile per hour in total control doesn’t usually come with stock gearing, especially with manual transmissions. A low crawl ratio is also an asset on descents, where using engine breaking is preferred over using the foot brakes. The availability of low gearing doesn’t hurt at high altitudes, when the rarefied air has sapped half your engine power. A deep crawl ratio is less important to a desert Jeep, a mudder, or one that is used primarily in easy situations.
The “ideal” crawl ratio is a debatable topic and one that is subject to a great deal of personal preference. There are some rigs down to 350:1. They can idle in gear and tire movement is barely perceptible. Even without going to these extremes, it’s possible to go so low that first gear is essentially useless 99.9 percent of the time. Also, the needs of a manual trans and an automatic are quite different.
The crawl ratio needed depends on the type of terrain encountered and how much low-end torque your engine develops. A big, torquey engine can get by with a higher ratio than can a four-cylinder. The key is to be low enough that the engine can essentially ideal over obstacles at a very low speed without constantly stalling or forcing the driver to slip the clutch. Automatics are a little more forgiving in that regard. Generally, manuals need lower crawl ratios than automatics.
After quizzing a large number of 'wheelers, I'll go out on a limb and give some crawl ratio ranges. For general purpose wheeling with a manual transmission, a range of 40-60:1 will offer good all-around performance. For automatics in the same situations, 35-50:1 works well. For die-hard rockcrawlers with stick shifts, 60-100:1 and beyond can be beneficial. For automatics in the same situations, 45-60:1 works well.”
Citation: Allen, Jim. "Chapter 5/HOW LOW SHOULD YOU GO?" Jeep 4X4 Performance Handbook. St. Paul: Motor/MBI, 2007. N. pag. Print.
Canada - Nat'l Capital Region
Know your angles before approaching obstacles and
follow the general rule of off-roading, "Go as slow as you can, as fast as you must."
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