What is your crawl ratio?

Chris_Keziah said:
Current:
42RLE 1st: 2.81
NP231: 2.72
The Dana's: 4.88
Crawl Ratio: 37.56 (With TQ Factor of 1.5:1 = 56.34)

Hopefully soon to be setup:
NV3550: 4.01
NP231: 2.72
The Dana's: 4.88
Crawl Ratio: 53.03 (If I can fit it, I'm thinking of adding NWF EcoBox which would make it 144.25 in 1st and 83.81 in 2nd)
Click to expand...

What are you going to put behind that NWF box?

shawn said:
Save your pesos.
Click to expand...

Why? I've been looking into them for my xj.
 
ghost said:
Why? I've been looking into them for my xj.
Click to expand...

A couple of people have already posted in this thread and explained why, but I'll restate it.

A 50-60:1 crawl ratio is plenty for a 4.0L Jeep. The 4cyl could benefit from a bit higher ratio (less torque), but that's it. The higher the ratio, the harder it is to get wheel speed and maintain momentum. BTDT, you end up driving around all day in 3rd/4th/5th, or (if doubler), running one case in high gear.
 
shawn said:
Save your pesos.
Click to expand...

I am for now, may just find a Rubi case. Kinda want to see how I like the manual gear ratios first before doing anything. I've seen me drive and there usually ain't nothing slow about it.

ghost said:
What are you going to put behind that NWF box?.
Click to expand...

The 231 until the 4.0L kills it
 
shawn said:
A couple of people have already posted in this thread and explained why, but I'll restate it.

A 50-60:1 crawl ratio is plenty for a 4.0L Jeep. The 4cyl could benefit from a bit higher ratio (less torque), but that's it. The higher the ratio, the harder it is to get wheel speed and maintain momentum. BTDT, you end up driving around all day in 3rd/4th/5th, or (if doubler), running one case in high gear.
Click to expand...


This


I was in 3rd to "bounce" up on the Potts rock
 
Last edited:
shawn said:
A couple of people have already posted in this thread and explained why, but I'll restate it.

A 50-60:1 crawl ratio is plenty for a 4.0L Jeep. The 4cyl could benefit from a bit higher ratio (less torque), but that's it. The higher the ratio, the harder it is to get wheel speed and maintain momentum. BTDT, you end up driving around all day in 3rd/4th/5th, or (if doubler), running one case in high gear.
Click to expand...
I can understand that. It seems like sometimes my 205 in low is too high and doubled to 3.8 it too low. So i was thinking a 2.72 option would be nice.
 
168:1 haha

3.83 R150 trans
4.7 crawl box
2.28 rear case
4.10 axles

I had originally planned to build the truck to race, found a good deal on a set of the super heavy duty Marlin crawler 4.7's so I put them in to run a single case. Then I thought that going fast in low range would not be possible, so I added another case to get the stock low range gear back. In hindsight I would have been better off with just dual cases and no 4.7's.
 
What Shawn said. My truck is heavy, 6500 lbs, and underpowered at around 200 to 225 estimated HP on 42s and the only time I use double low it to show off like idling up lower rock garden. I think only once or twice have I actually used double low and 2nd or 3rd gear in the 435 (and I count them L, 1,2,3) to get up something because single low granny wasn't quite enough without clutch slipping. But that was a rare occasion and I could have done it in single low anyway.

My truck and the early full size Broncos had a very short front driveshaft, I had to run 2 Tom woods "wobble joints" to keep it from binding. After one broke on the same trip my rear double cardan blew apart and I was stuck in no wheel drive and needing two driveshaft cause I never found the front slip yoke I put the doubler together. On my rig with 115" wb that puts both driveshaft within a few inches of each other in length and I don't need the shitty vibrating joints.

Sent from my HTC6545LVW using Tapatalk
 
ghost said:
So i was thinking a 2.72 option would be nice.
Click to expand...

That's a little bit different, and an easier sell. If you have a 1.98 low range and a 4ish:1 first gear, you're a bit undergeared for starters, but the 2.72 reduction box has the benefit of splitting your existing ratios to give you "in-between" gears. You'll probably find that the low/low ratio is too low in general, but it gives you options.

The other thing that nobody talks about with the super-low t-case gears is that with an auto trans: you often have to change the torque converter to keep the trans from driving through the brakes.
 
120.5

R151F 4.31
Toy crawl box 2.28
Cruiser splitcase 2.28
Axles 5.38

I’ve used double low 1st/2cnd crawling often on the east coast and it’s fine. Or 3rd for a bump. Single low 2cnd gear for climbs or gtfo of the way side step clutch dump bumps.
There have been plenty of times out west when I wish I was lower. Usually dumb rear steer lines or technical climbs where it’s a long way to the bottom or you know that flop/roll is gonna hurt.

I belly out on the big ledge on mason jar in Harlan so I just clutch dump it and kinda jump it:burnout:
248666F3-ADDE-4415-9EB6-1A0F50578671.jpeg
 
Joe J. said:
I wonder if there is a better figure we can baseline from? Like how my crawl ratio isn't great but I try to keep my rig light weight because I know it will work better if I do and keeping it light helps keep parts alive too. Or how horsepower can make up for the lack of gears or weight.

Sent from my XT1254 using Tapatalk
Click to expand...
<flamesuit>
I think basically it comes down to needing about 75% more driving force than the weight of the vehicle. You can get by on alot less, but thats where you have to employ clutch slippage or tirespin. To put some numbers to it, lets use a couple examples:
4000lb TJ, 4.0, 35" tires, 50:1 crawl ratio (pretty close to a stock driveline TJ on 35's)
The 4.0 has been shown to output about 210ft-lbs at the wheels. 210*50=10500ft-lbs in low range, first gear. Since the tires are 35" tall, to convert ft-lbs into force at the wheel, you take 12" (1ft) and divide by the radius of the tire (17.5"), and then multiply that by 10500ft-lbs. That results in a potential propulsion force of (12/17.5)*10500=7200lbs-force. This is only useful if you have enough traction and the driveline is strong enough to handle it.

So now that the math is laid out, here are some numbers in quick sequence:
3500lb TJ, 2.5, 32's, 30:1=2813 lb-f
3500lb TJ, 2.5, 32's, 50:1=4688 lb-f
3500lb TJ, 2.5, 32's, 70:1=6563 lb-f (188%)
3500lb TJ, 2.5, 32's, 1000:1=9375 lb-f
3500lb TJ, 2.5, 32's, 200:1=18750 lb-f


4000lb TJ, 4.0, 35's, 30:1=4320 lb-f
4000lb TJ, 4.0, 35's, 50:1=7200 lb-f (180%)
4000lb TJ, 4.0, 35's, 70:1=10080 lb-f
4000lb TJ, 4.0, 35's, 100:1=14400 lb-f
4000lb TJ, 4.0, 35's, 200:1=28800 lb-f

6000lb truggy, 300ft-lb V8, 40's, 30:1=5400 lb-f
6000lb truggy, 300ft-lb V8, 40's, 50:1=9000 lb-f
6000lb truggy, 300ft-lb V8, 40's, 70:1=12600 lb-f (210%)
6000lb truggy, 300ft-lb V8, 40's, 100:1=18000 lb-f
6000lb truggy, 300ft-lb V8, 40's, 200:1=36000 lb-f

3000lb buggy, 125ft-lb 4cyl, 37's, 30:1=2432 lb-f
3000lb buggy, 125ft-lb 4cyl, 37's, 50:1=4054 lb-f
3000lb buggy, 125ft-lb 4cyl, 37's, 70:1=5676 lb-f (189%)
3000lb buggy, 125ft-lb 4cyl, 37's, 100:1=8108 lb-f
3000lb buggy, 125ft-lb 4cyl, 37's, 200:1=16216 lb-f

7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 30:1=5455 lb-f
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 50:1=9091 lb-f
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 70:1=12727 lb-f (182%)
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 100:1=18182 lb-f
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 200:1=36364 lb-f

Here's a spreadsheet for more analysis if ya wanna look at more numbers:
upload_2018-7-20_11-43-26.png


</flamesuit>
 
I think my new rig is 55to 1 and I feel like it’s almost to much on 39s with an ls and auto I almost never use first unless I’m in a very technical spot

Ls1
Turbo 350 tci lower gear kit
Atlas 4to1
488 axle gears
3900 pounds


Sent from my iPhone using Tapatalk
 
jeepinmatt said:
<flamesuit>
I think basically it comes down to needing about 75% more driving force than the weight of the vehicle. You can get by on alot less, but thats where you have to employ clutch slippage or tirespin. To put some numbers to it, lets use a couple examples:
Click to expand...

If you need something to do, I have some redlines. Do you know Revit?
 
jeepinmatt said:
<flamesuit>
I think basically it comes down to needing about 75% more driving force than the weight of the vehicle. You can get by on alot less, but thats where you have to employ clutch slippage or tirespin. To put some numbers to it, lets use a couple examples:
4000lb TJ, 4.0, 35" tires, 50:1 crawl ratio (pretty close to a stock driveline TJ on 35's)
The 4.0 has been shown to output about 210ft-lbs at the wheels. 210*50=10500ft-lbs in low range, first gear. Since the tires are 35" tall, to convert ft-lbs into force at the wheel, you take 12" (1ft) and divide by the radius of the tire (17.5"), and then multiply that by 10500ft-lbs. That results in a potential propulsion force of (12/17.5)*10500=7200lbs-force. This is only useful if you have enough traction and the driveline is strong enough to handle it.

So now that the math is laid out, here are some numbers in quick sequence:
3500lb TJ, 2.5, 32's, 30:1=2813 lb-f
3500lb TJ, 2.5, 32's, 50:1=4688 lb-f
3500lb TJ, 2.5, 32's, 70:1=6563 lb-f (188%)
3500lb TJ, 2.5, 32's, 1000:1=9375 lb-f
3500lb TJ, 2.5, 32's, 200:1=18750 lb-f


4000lb TJ, 4.0, 35's, 30:1=4320 lb-f
4000lb TJ, 4.0, 35's, 50:1=7200 lb-f (180%)
4000lb TJ, 4.0, 35's, 70:1=10080 lb-f
4000lb TJ, 4.0, 35's, 100:1=14400 lb-f
4000lb TJ, 4.0, 35's, 200:1=28800 lb-f

6000lb truggy, 300ft-lb V8, 40's, 30:1=5400 lb-f
6000lb truggy, 300ft-lb V8, 40's, 50:1=9000 lb-f
6000lb truggy, 300ft-lb V8, 40's, 70:1=12600 lb-f (210%)
6000lb truggy, 300ft-lb V8, 40's, 100:1=18000 lb-f
6000lb truggy, 300ft-lb V8, 40's, 200:1=36000 lb-f

3000lb buggy, 125ft-lb 4cyl, 37's, 30:1=2432 lb-f
3000lb buggy, 125ft-lb 4cyl, 37's, 50:1=4054 lb-f
3000lb buggy, 125ft-lb 4cyl, 37's, 70:1=5676 lb-f (189%)
3000lb buggy, 125ft-lb 4cyl, 37's, 100:1=8108 lb-f
3000lb buggy, 125ft-lb 4cyl, 37's, 200:1=16216 lb-f

7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 30:1=5455 lb-f
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 50:1=9091 lb-f
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 70:1=12727 lb-f (182%)
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 100:1=18182 lb-f
7000lb Overlanding Rover, 250ft-lb 4.4v8, 33's 200:1=36364 lb-f

Here's a spreadsheet for more analysis if ya wanna look at more numbers:
View attachment 272473

</flamesuit>
Click to expand...
Nice! I only figured it down to the torque to the tire last night and that's as far as I could get but you ran with it. That 75% more force than weight sounds good to me.

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Jody Treadway said:
It ain't the 4.0 that'll kill it. It'll be the torque from the crawl box that does
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Yep. I'm seeing 300's getting eaten by 231 crawl boxes I can only imagine how fast a 231 with a NWF box would die......
 
GONOVRIT said:
120.5

R151F 4.31
Toy crawl box 2.28
Cruiser splitcase 2.28
Axles 5.38

I’ve used double low 1st/2cnd crawling often on the east coast and it’s fine. Or 3rd for a bump. Single low 2cnd gear for climbs or gtfo of the way side step clutch dump bumps.
There have been plenty of times out west when I wish I was lower. Usually dumb rear steer lines or technical climbs where it’s a long way to the bottom or you know that flop/roll is gonna hurt.

I belly out on the big ledge on mason jar in Harlan so I just clutch dump it and kinda jump it:burnout:
Click to expand...

Someone who loves you must set up your gears :p
 
Tim C said:
What Shawn said. My truck is heavy, 6500 lbs, and underpowered at around 200 to 225 estimated HP on 42s and the only time I use double low it to show off like idling up lower rock garden. I think only once or twice have I actually used double low and 2nd or 3rd gear in the 435 (and I count them L, 1,2,3) to get up something because single low granny wasn't quite enough without clutch slipping. But that was a rare occasion and I could have done it in single low anyway.

My truck and the early full size Broncos had a very short front driveshaft, I had to run 2 Tom woods "wobble joints" to keep it from binding. After one broke on the same trip my rear double cardan blew apart and I was stuck in no wheel drive and needing two driveshaft cause I never found the front slip yoke I put the doubler together. On my rig with 115" wb that puts both driveshaft within a few inches of each other in length and I don't need the shitty vibrating joints.

Sent from my HTC6545LVW using Tapatalk
Click to expand...

I need a longer front driveshaft as well. Thinking about adding a crawlbox in front of my Atlas to aid in gearing as well as driveline length
 
Chris_Keziah said:
Current:
42RLE 1st: 2.81
NP231: 2.72
The Dana's: 4.88
Crawl Ratio: 37.56 (With TQ Factor of 1.5:1 = 56.34)

Hopefully soon to be setup:
NV3550: 4.01
NP231: 2.72
The Dana's: 4.88
Crawl Ratio: 53.03 (If I can fit it, I'm thinking of adding NWF EcoBox which would make it 144.25 in 1st and 83.81 in 2nd)
Click to expand...

Let’s talk about your 42RLE sometime, I am thinking of ditching my AX15, maybe we could work something out.
 
The "75% extra" theory is interesting. It doesn't really take into consideration how fast you'll be moving at that gear ratio at idle, only that there's enough oomph to keep you moving.

One long discussion I saw about this on pirate years ago had two main takeaways:

Tire size x pi = roughly what you want to shoot for for technical crawling... 60ft per min or 1ft per sec at idle-ish - so essentially ~100:1 or better with a manual, and half that with an auto because of the torque converter reduction.

Second thing was pretty obvious - engine power will determine how far off from that you can be and still be comfortable. Good torque off idle, you can be (numerically) lower, but if you are running a 1.3 in a sami, you need a bit more gear.

But a lot of those dudes in that discussion were out West and didn't deal with as much need for wheel speed. I think an auto is probably better out east because you can two foot it through the technical stuff and blast off when you need to, instead of having to shift your range box into high and grab 2nd.
 
Only truck running and driving currently is my GMC, but it’s got a pretty good crawl ratio for a 2wd.

7.05 first gear x 8.10 (axle low side): 57:10
 
I'm reminded of wheeling with a Marlin Crawler group out west. Duder would pull up on an obstacle, engine banging the rev limiter [baaaaa ba ba baaaaaa babada baaaaa ba ba baaaaa] tires baaaaarely fucking moving. "Hey Bill, are you in first, first low high low low?" "Nah, this is first second high low low low." "Oh, well you might want to kick it down a gear, this ledge is a little bigger than the last one" <ker chunk ker chunk> [baaaaa ba babadagagada ba baaaaaa babadagada baaaaa ba bababada ba baaaaa]

Fuuuuuuuuck.
 
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