How to calculate a vehicle's crawl ratio

[@supremeflagship8965]

Theoretically you can build a 4WD vehicle with extreme crawl ratio. A combination of GM Muncie SM420 transmission (with it's very low 1st gear ratio of 7.05:1), Suzuki Jimny transfer case with 6.5:1 low gear ratio (there are Atlas 4-speed transfer cases with 11.69:1 low ratio), Dana 60 axle with 7.17:1 diff ratio will give you a crawl ratio of 328.56:1 (590.9:1 with Atlas 4sp t-case). But I have a hunch that such crawl ratios are excessive. So... what's the most practical crawl ratio?

[@Nik-ok9nu]

You also need to factor in the size of the tire, not for the crawl ratio, but for your crawl speed.

[@nfoederer]

running 3.68 1st gear, 6.5:1 tcase, 7.17 in the diffs at about 175:1

[@ryanlester761]

Good info Jimmy. I don't have a crawl ratio, but I mix my chainsaw gas/oil ratio at 50:1... if that counts. :)

[@alejandrochapa4707]

How tire size ( e.g. from 35s to 39s ) affect/influence crawl ratio?

[@SnailTrail4x4]

Alejandro Chapa -- the ratio is still the same. Tires are not apart of the equations. This is all about the different gearing. You will still have the same crawl ratio no matter what size tires you have. You will just be traveling faster with big tires.

[@alejandrochapa4707]

SnailTrail----You are right, I realized about it using Advance Adapters' crawl ratio calculation charts early this week but still have questions to you----How tire size modification affects wheel's torque ( from 35 to 39 )? Assume there is a lost/win difference doing that ( I saw some formulas to calculate it but need further explanation and my JK' s technical data to complete the math/equations. In addition I would like to know how torque converter on my transmission ( 42RLE ) affect/influence all this matter together. Thanks for your input...nice videos

[@MrGhadnaz1]

@@alejandrochapa4707 Tire size does not affect the wheel torque. It affects the force and resultantly the acceleration. Torque at the flywheel* crawl ratio= wheel torque

[@AZWESTSIDEWHEELERS]

Great video good information for everyone. I was curious I saw a discussion on crawl ratio can’t remember where in the difference between automatics and manual transmissions they were saying with an automatic to multiply by 1.5 or two to account for the torque converter changing things. It would make sense because in Moab I tested it out our cousin has a jeep with a manual transmission and his crawl ratio was supposedly higher than mine. Mine right now is 47 and his was 57.4 but in first gear I crawl a lot slower than him. If I multiply by 1.5 for Torque Converter I’m at 70.5 which would be about right on how slow I am in first gear versus my cousins at 57.4. Will be going to 5.13 Gears hopefully soon which Will bring me up to 58.28 or 87.42 multiplied by 1.5. Would like to get around someone with multiple T cases like yourself to test the 1.5 multiple theory out more.

[@SnailTrail4x4]

+AZ WESTSIDE WHEELERS -- I've never heard that but it makes a little bit of sense, those torque converters do steal some power. I wonder if anybody else has a comment.

[@overlandbug6028]

Wait im at 437.1 42rle 2.84, 4.88 axle, rubicrawler 2.70 , atlas 4speed 11.70

[@Jeeptalkshow]

Well I thought 48 was a good crawl ratio until I saw yours. I can barely keep mine from moving with two feet on the brakes. I guess you use and anchor. ;)

[@SnailTrail4x4]

Total horse power and torques come into these factors also

[@draculaS2k]

Alright. Sooo i have a 2011 tacoma 4x4 with Arb air lockers f&r that im in the process of finishing my 5.3ls swap. 4l60e Transmission first gear 3.06 Np261 Transfer case 2.76:1 Axles gears 4.88s = 41.2145....... Is this bad? Ohh yea im on 35X12.50 17$ GY Kevlar mtrs

[@SnailTrail4x4]

With that LS your going to have tons of HPs and that's going to help alot. But if your planning on doing any serious rock crawling it's always nice to have a bigger number.

[@draculaS2k]

10/4 thank bud.

[@thecatalyst7743]

Manual transmission you need 100+ ratio. Automatic anything around 50-80 work good.

[@SnailTrail4x4]

I think there are a lot of factors that fall into this, size of your engine, and tires play a big roll.

[@hurleykid83]

I'm thinking about doing triple cases.. which is 3.95x2.28x4.7x4.7x5.29=1052:1.. .. ya. Or 3.95x2.28x2.28x4.7x5.29=510:1... 4runner with 40s help me decide.. lol.

[@SnailTrail4x4]

+hurleykid83 -- in my opinion 1000:1 is just to low, and you would never use it. Like I said in my video I practically never use my lowest of low gears 224:1. So I would advise doing the 510:1. Though it would be pretty badass to say I have a 1000:1 crawl ratio 😉

[@hurleykid83]

Yea it more for showing off then anything.. gotta have the radesigns triple stick setup..

[@SnailTrail4x4]

+hurleykid83 I'd be interested to see pics of your setup. When your doing the install post some pics on The FB page please 😀

[@danzoller7397]

Killer break down on crawl ratios, ya forgot tripple t case also like marlins & others! Only in a Toyota :-)

[@danzoller7397]

Marlin has 2.28x 4.7x.4.7 not sur what trans gear hes got these days but have personally seen that t case set up with 6.5 :1 1st gear way low

[@SnailTrail4x4]

+Dan zoller -- what's your crawl ratio with tripple cases?

[@danzoller7397]

SnailTrail4x4 not mine a good buddys rig 1794.15:1 redulous ! 6.5 x2.28x4.7x4.7x 5.40

[@TrailCoMedia]

Hey, Jimmy, you went over 2:00. This is false advertising. And, I want my money back.

[@SnailTrail4x4]

+Brenan Greene -- I will give you the tenth of a penny I might have earned 😉