How to determine crawl ratio?

[Lightsped]

What is the method used to determine the crawl ratio for a vehicle? Or is it simply a matter of looking at a spec sheet?

Currently own a Tacoma TRD Off Road 6 speed manual which comes with 4.30 rear gears. How will this compare with the current JL owned with 3.45 rear gears with 6 speed manual?

Or am I missing something? Still feel kind of new to the whole off road thing.....

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[SG19JLUR]

You need to look at the ratio of the low range of the transfer case. In a Rubicon that ratio is 4:1. In very simple terms, it magnifies the rear axle ratio by a factor of 4. I'm not saying the rear axle ratio doesn't matter, but the transfer case low range plays a much greater role than the rear axle ratio in determining your crawl ratio.

Edit: the tire size also plays a role. Smaller tires will provide a better crawl ratio, but you would be sacrificing traction.

 

[DavidArmen]

The crawl ratio is the ratio of the first gear of the transmission multiplied by the low gear of the transfer case multiplied by the axle ratio.

My jeep rubicon has first gear at 4.71, my transfer case low is 4.00 and my differential ratio is 4.10
4.71 x 4.00 x 4.10 = 77.25

So my crawl ratio is 77.25 to 1

 

[DavidArmen]

Some more examples:

Non-Rubicon Wrangler with manual transmission-
Transmission first gear: 5.13 to 1
Transfer case Low range 2.72 to 1
Differential: 3.45 to 1

5.13 x 2.72 x 3.45 = 48.14

So a Non-Rubicon Jeep JL with a manual transmission and 3.45 gears has a crawl ratio of 48.14 to 1.

Because of the very high first gear of the manual transmission, the rubicon with the manual gets the highest crawl ratio of any production vehicle:
Transmission first gear: 5.13 to 1
Transfer case Low range 4.00 to 1
Differential: 4.10 to 1

5.13 x 4.00 x 4.10 = 84.13

So the manual tranny rubicon has a crawl ratio of 84.13 to 1.

I’m sure you know what that ratio meant but for those who don’t, 84.13 to 1 means that for every ome rotation of the driving tires, the engine crankshaft must rotate 84.13 times.

That also effectively multiples the torque going to the wheels from the engine by 84.13 times. So if you have the V6 Pentasutar that makes I believe 260 pound-feet of torque,
(260 x 84.13 = 21,874) so the tires combined together are getting 21,874 pound-feet of torque.

 

[Lightsped]

Wow, nice. Thanks for the detailed info.

How will the Tacoma (4.30) compare with the JL (3.45) on the trails? I haven't had a chance to get the JL off road yet. Currently 500 miles on the odometer..... Again, both vehicles are stock, V-6 powered and manual 6 speed.

 

[Sean L]

Wow, nice. Thanks for the detailed info.

How will the Tacoma (4.30) compare with the JL (3.45) on the trails? I haven't had a chance to get the JL off road yet. Currently 500 miles on the odometer..... Again, both vehicles are stock, V-6 powered and manual 6 speed.

1st gear: 3.98
Low range: 2.57
Axle Ratio: 4.3

43.98 crawl ratio for a Tacoma TRD Pro with six speed manual.

 

[Reinen]

Wow, nice. Thanks for the detailed info.

How will the Tacoma (4.30) compare with the JL (3.45) on the trails? I haven't had a chance to get the JL off road yet. Currently 500 miles on the odometer..... Again, both vehicles are stock, V-6 powered and manual 6 speed.

Keep in mind that these numbers only tell you how slowly the wheels can turn and with what torque. How the vehicles compare on the trails involves many other factors such as how well the suspension and tires transfer that torque to the ground and move the vehicle. You could have the best crawl ratio and torque in the world but if the tires and suspension don't transfer it to the ground well, it's useless.

 

[intentsrig]

It’s going to be super similar in terms of stall speed. Your tacoma has a 43:1 crawl ratio which is less than the sport JL but not by much.

I’d recommend disconnecting your sway bars either manually with a few wrench’s or get some quick disconnects. Won’t help with stalling out but will allow you to get over rocks and obstacles easier which will keep forward momentum.

Next, buy a rubicon transfer case lol. Best upgrade.

Simple calculator https://www.crawlpedia.com/crawl_ratio_calculator.htm
And this one tells your fpm. No need to put in each gear ratio. Just do 1st.
http://www.grimmjeeper.com/gears.html

 

[Lightsped]

Yes, 43.98 (Toyota) verses a 48.14 (JL). Not sure why, but I thought the Toyota would have a higher crawl ratio....

 

[calemasters]

The crawl ratio is the ratio of the first gear of the transmission multiplied by the low gear of the transfer case multiplied by the axle ratio.

My jeep rubicon has first gear at 4.71, my transfer case low is 4.00 and my differential ratio is 4.10
4.71 x 4.00 x 4.10 = 77.25

So my crawl ratio is 77.25 to 1

Yup. So you have torque multiplication of 77.25:1 from the engine crank to the axles. And for those of us with only 2 pedals, we also have in addition to this, hydraulic torque multiplication through the torque convertor. So Jeep owners are never torque limited, only traction limited.

 

[Sean L]

Yes, 43.98 (Toyota) verses a 48.14 (JL). Not sure why, but I thought the Toyota would have a higher crawl ratio....

Their transfer cases's "low" range isn't very low compared to the Jeeps.

 

[DavidArmen]

Keep in mind that these numbers only tell you how slowly the wheels can turn and with what torque. How the vehicles compare on the trails involves many other factors such as how well the suspension and tires transfer that torque to the ground and move the vehicle. You could have the best crawl ratio and torque in the world but if the tires and suspension don't transfer it to the ground well, it's useless.

perfectly put!

Wow, nice. Thanks for the detailed info.

How will the Tacoma (4.30) compare with the JL (3.45) on the trails? I haven't had a chance to get the JL off road yet. Currently 500 miles on the odometer..... Again, both vehicles are stock, V-6 powered and manual 6 speed.

The Tacoma has an IFS, so it already has a disadvantage there when compared to all JLs which Ave solid live axles front and rear. The JL will have more articulation on the trails. This is debatable and is only my opinion.

 

[Zandcwhite]

perfectly put!




The Tacoma has an IFS, so it already has a disadvantage there when compared to all JLs which Ave solid live axles front and rear. The JL will have more articulation on the trails. This is debatable and is only my opinion.

I agree 100% for low speed trails, especially in the rocks. Now take them both out in the desert and bomb around at 70+mph and the Tacoma will ride much better, feel much more stable, and be able to carry more speed through the rougher sections. There are benefits and drawbacks to both. For off roading at low to moderate speeds I prefer the Jeep. For higher speeds both on and off road the ifs has the advantage.

 

[word302]

You need to look at the ratio of the low range of the transfer case. In a Rubicon that ratio is 4:1. In very simple terms, it magnifies the rear axle ratio by a factor of 4. I'm not saying the rear axle ratio doesn't matter, but the transfer case low range plays a much greater role than the rear axle ratio in determining your crawl ratio.

Edit: the tire size also plays a role. Smaller tires will provide a better crawl ratio, but you would be sacrificing traction.

Tire size does not effect the crawl ratio. Crawl ratio is simply axle gear ratio x transfer case low ratio x transmission low gear (1st gear) ratio.

 

[word302]

Some more examples:

Non-Rubicon Wrangler with manual transmission-
Transmission first gear: 5.13 to 1
Transfer case Low range 2.72 to 1
Differential: 3.45 to 1

5.13 x 2.72 x 3.45 = 48.14

So a Non-Rubicon Jeep JL with a manual transmission and 3.45 gears has a crawl ratio of 48.14 to 1.

Because of the very high first gear of the manual transmission, the rubicon with the manual gets the highest crawl ratio of any production vehicle:
Transmission first gear: 5.13 to 1
Transfer case Low range 4.00 to 1
Differential: 4.10 to 1

5.13 x 4.00 x 4.10 = 84.13

So the manual tranny rubicon has a crawl ratio of 84.13 to 1.

I’m sure you know what that ratio meant but for those who don’t, 84.13 to 1 means that for every ome rotation of the driving tires, the engine crankshaft must rotate 84.13 times.

That also effectively multiples the torque going to the wheels from the engine by 84.13 times. So if you have the V6 Pentasutar that makes I believe 260 pound-feet of torque,
(260 x 84.13 = 21,874) so the tires combined together are getting 21,874 pound-feet of torque.

Not to nitpick but I see this all the time. A higher numerical value = lower gear. 100:1 crawl ratio is lower than 50:1. I added lower (5.13) gears to my rubicon (factory 4.10 ratio). I know it’s semantics but this is confusing enough for most people without twisting terms around.

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