Crawl ratio

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Phils67
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Re: Crawl ratio

Postby Phils67 » Wed Jun 20, 2018 4:27 am

Then i am sold. Ill stick with my plans of going 3.73s giving me the 48ish crawl ratio
1967 J2000/ 4.0MPI/T18/D20/35s

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Lumpskie
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Re: Crawl ratio

Postby Lumpskie » Wed Jun 20, 2018 4:58 am

Just a thought... Another thing you could always do is add a hand throttle to the mix.
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derf
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Re: Crawl ratio

Postby derf » Tue Jun 26, 2018 3:11 pm

One idea for over-thinkers is to modify the transfer case. You can get a 3.15:1 low range gear kit like this one: https://teraflex.com/shop_items/low20-g ... -automatic

Combine something like that with a more highway friendly gear ratio in the axles and you get a better range of performance. You get lower RPMs driving down the highway but then when you shift into low range, you get good crawling.

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Phils67
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Re: Crawl ratio

Postby Phils67 » Tue Jun 26, 2018 4:18 pm

I like the way you think. Its a future possibility...
1967 J2000/ 4.0MPI/T18/D20/35s

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tedlovesjeeps71
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Re: Crawl ratio

Postby tedlovesjeeps71 » Tue Jun 26, 2018 5:02 pm

Crawl box...

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Phils67
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Re: Crawl ratio

Postby Phils67 » Tue Jun 26, 2018 5:04 pm

tedlovesjeeps71 wrote:Crawl box...

....go on...?
1967 J2000/ 4.0MPI/T18/D20/35s

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tedlovesjeeps71
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Re: Crawl ratio

Postby tedlovesjeeps71 » Tue Jun 26, 2018 6:11 pm

Phils67 wrote:
tedlovesjeeps71 wrote:Crawl box...

....go on...?

I run a northwest fabworks crawl box in my scrambler. It allows me to use the regular gears/t-case hi-low, or put the crawl box in low and the other stuff in whatever. Gives me a wider range of gearing options for different situations. Sometimes low/low is too low. If you do the transfer case reduction swap you may find hi is too high and the new low is too low. I like options.

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Gives me options.

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will e
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Re: Crawl ratio

Postby will e » Tue Jun 26, 2018 9:28 pm

That's a cool setup. Mine is similar. I went with the Atlas 4 speed. The transfer case is 2:1 and with a twin stick. In between the transmission and the transfer case is a 2.72 to 1 planetary gear. So I can go 1:1 1:2 1:2.72 or 1:5.44.

When deciding what to do with my rig I looked at this option or going with a 4 speed automatic. The costs were similar. With the 4 speed I could go lower axle gearing and make up the difference with the overdrive. With the Atlas I could go with taller axles gears (4.54 and 37" tires) and stick with the 3 speed 727. Since my rig isn't a daily driver I decided the flexibility of the Atlas was more favorable compared to a 4 speed auto transmission.

It all just depends on what you are doing with the rig.
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tedlovesjeeps71
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Re: Crawl ratio

Postby tedlovesjeeps71 » Tue Jun 26, 2018 9:53 pm

Yeah, the 4 sp atlas is a good setup. I couldn't afford it and stumbled on someone selling the BB. When my T5 grenades I knew it was time to step up. The NV4500 has plenty of 1st gear grunt (similar to the OPs t18) and the BB allows me to double that. I was able to keep my diff gears at 4:10 with 35s, keep the use of 5th gear, run 80mph and when I get to the trails I can choose a gear for the obstacles at hand.

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Phils67
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Re: Crawl ratio

Postby Phils67 » Wed Jun 27, 2018 4:02 am

Thats pretty cool but would it work with a Dana 20 that has a "texas" bolt pattern?
1967 J2000/ 4.0MPI/T18/D20/35s

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derf
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Re: Crawl ratio

Postby derf » Wed Jun 27, 2018 6:44 am

I have the 4 speed Atlas in my JK. But I went with the 2.72/4.3/11.7 combo. I do most of my wheeling in 4.3 low. But when I need it for a very technical crawl, I shift into super-low (238:1 final combined). It gives me a ton of control and finesse.

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derf
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Re: Crawl ratio

Postby derf » Wed Jun 27, 2018 7:23 am

Phils67 wrote:Thats pretty cool but would it work with a Dana 20 that has a "texas" bolt pattern?


Probably not. There is very little these days that isn't focused around the Jeep Dana300/NP2xx bolt pattern. Parts like that for the older transfer cases are getting harder to come by. You can still rebuild them easily enough but significant modifications like a crawl box just aren't out there.

jeepininawk
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Re: Crawl ratio

Postby jeepininawk » Mon Sep 10, 2018 10:39 pm

My crawl ratio will be around 48:1 or so, I forget. It'll be a nv4500 with a divorce 205 case and 3.55 or maybe but doubtful a 3.73 ring gear. Rolling on 35's and powered by a VORTEC 454.

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tedlovesjeeps71
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Re: Crawl ratio

Postby tedlovesjeeps71 » Tue Sep 11, 2018 8:35 am

jeepininawk wrote:My crawl ratio will be around 48:1 or so, I forget. It'll be a nv4500 with a divorce 205 case and 3.55 or maybe but doubtful a 3.73 ring gear. Rolling on 35's and powered by a VORTEC 454.

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I'm only at about 180:1 but I don't have as much motor as you do.

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Stuka
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Re: Crawl ratio

Postby Stuka » Tue Sep 11, 2018 11:04 am

Any crawl ratio beyond 75:1 basically makes horse power irrelevant unless you have gigantic tires. You can have a 20hp B&S and crawl just fine in most cases.

The only real place that power matters is in high range. 35's with 3.55's for instance is not going to be great when climbing grades and puts a lot of stress on u-joints. The 454 should have enough grunt for it, but it won't be ideal.
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tedlovesjeeps71
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Re: Crawl ratio

Postby tedlovesjeeps71 » Tue Sep 11, 2018 11:18 am

Stuka wrote:Any crawl ratio beyond 75:1 basically makes horse power irrelevant unless you have gigantic tires. You can have a 20hp B&S and crawl just fine in most cases.

The only real place that power matters is in high range. 35's with 3.55's for instance is not going to be great when climbing grades and puts a lot of stress on u-joints. The 454 should have enough grunt for it, but it won't be ideal.



Not as bad as an anemic 360 turning 33s with 272s...


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