Advice on getting a better crawl ratio

BigClay

BigClay

Knower of useless ZJ things
Joined
Sep 24, 2008
Location
Winston-Salem
I am thinking long term here, so all suggestions are appreciated. I currently have a 231 transfer case behind my AX15 in my TJ. I am looking at options to give me a better crawl ratio centered around the transfer case (not talking about diff gears here).

So my first thought was a Tera 4:1 kit on my current 231, but many things I have read said the Tera gears are junk.

Next thought was an Atlas, but those are pricey.

Next is a d300, but I am not sure how much labor and effort that will take to make it work with my setup.

Finally I thought about swapping a NVG241OR from a Rubicon into my jeep.

I am trying to do the most cost effective route but still not shooting myself in the foot down the road. I am leaning towards the NVG241OR case in, for simplicity and bidget reasons.

So what are your thoughts?
 
D300 is pretty easy to bolt in, the complication is shifters. Down East Offroad sold the original flip kits with levers coming out the top of the box, I've personally made a couple where the levers come out the back of the case (works great, but packaging is difficult), and to me the simplest option is to get the cable shifter kit that allows you to just flip it and have a cable shifter setup.

Be very critical of the posts saying the Tera gears are junk. I've heard a million people say that, but only seen a couple firsthand instances.
 
How much are rubi tcases going for these days? A d300 would give you a worse ratio than the 231 unless you geared it. By the time you did that and put hd outputs in you'd have a good bit tied up. I'm in about the same boat as you but I've got a np435 to swap in and don't know if it's worth going d300 or just pony up for an atlas. Have you considered a transmission swap like 4500, 435, or 465? That would get you much better gearing and replace a weak link.
 
jeepinmatt said:
D300 is pretty easy to bolt in, the complication is shifters. Down East Offroad sold the original flip kits with levers coming out the top of the box, I've personally made a couple where the levers come out the back of the case (works great, but packaging is difficult), and to me the simplest option is to get the cable shifter kit that allows you to just flip it and have a cable shifter setup.

Be very critical of the posts saying the Tera gears are junk. I've heard a million people say that, but only seen a couple firsthand instances.
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I think the big thing is people think they can trail ride in low and overheat the case.
 
Me and a friend beat the snot out of a set of Tera gears in the same case and never had an issue. I wouldn't hesitate to run them behind a 4.0 unles they've changed in the last 7-8yrs.
 
RHSCTJ said:
I think the big thing is people think they can trail ride in low and overheat the case.
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I never had any issues trailriding in low, but honestly I don't think I ever did enough time without stopping to make a difference. What causes the problems in low that aren't caused in high? Obviously the gears are spinning 4 times as fast for the same input RPM, but I'd think 4hi on the street at 60mph would be worse than 4lo on the trail, averaging 10-15mph or less.
 
jeepinmatt said:
I never had any issues trailriding in low, but honestly I don't think I ever did enough time without stopping to make a difference. What causes the problems in low that aren't caused in high? Obviously the gears are spinning 4 times as fast for the same input RPM, but I'd think 4hi on the street at 60mph would be worse than 4lo on the trail, averaging 10-15mph or less.
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The "oil pump" is spun by the rear output shaft.
 
If you dont already own a D300.
By the time you get one and 4:1 kit and order reverse cable shifter and improve the outputs.
You are going to be spitting distance in price to an Atlas, unless you beg borrow trade and get lucky.

I dont know the going rate for the 241OR so I an compare that.


Oh if it were mine, Id do a doubler.
 
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231/231 doubler
 
@JC on here has an additional box behind his t case to have even further reduction after his 4:1 Rubi gears if I remember correctly. JC also has more money the me lol. Its not too costly tho considering you have the option of being that low when needed, and not so low when not needed.
Maybe he'll chime in and explain better.
 
I've never put a crawl box in a TJ so you may run into physical driveline length issues not fitting in such a short wheelbase. I've owned a dual tcase Yota and a good friend of mine had a Yota in a similar configuration with a single 4.7 case. Granted we are talking anemic 4 cylinders compared to a pretty torquey 4.0 so not exactly apples to apples. Both got the job done easily trying to crawl technical stuff without question. The problem came up when trying to run through terrain that had heavy drag like snow. Probably the same situation here as running on loose sand. You need lower gearing but not to the point you lose wheel speed. Similar situation on general trail terrain where you weren't necessarily on a rock face but not exactly flat ground running in hi range either. I always had a 2.28 lo to shift into where my buddy was either desert racing in hi range or crawling in 4.7 lo range. He lacked that middle ground which was really the sweet spot for anything other than rock crawling. I guess it boils down to what your needs really are.

I personally would run a 231/231 just based on cost and performance of what it will do. Strongest...nope. Quietest...nope. Will it get you into some deep gears quick and cheap...yup. I think the strength of that setup is pretty relative to what a stock 30 is going to handle with 33's so why not? If you blow it up just grab another spare, they are a dime a dozen and super easy to swap out.
 
I think it's all a waste of money.

Ours had 32/33" rubber with 4.10s and a 231, and it was all right. Now that it has the same rubber with 4.88s, it's sweet. Probably over-geared, if anything. With 33s and 4.56s, you should be perfect.

I was considering buying a Rubicon case for a while. Cost/benefit was about as good as it gets. I found a couple for right at $1k. I'd consider it again if I had a rig with taller diff gears and/or bigger tires, but that case is also a monster. You'd be looking at selling all the fancy belly skid crap you just bought.

I would not spend a dime on Tera gears. I think it's a bad design.
 
The average cost of acquiring a d300 and doing 4:1's and outputs is gonna be between $1300-$1600, not to mention the $65 clocking ring and however much for shifters.

I have 4.7/ax15/d300 with all the upgrades and gears. Running 42's and 5.38s. Grearing is not too bad on the street, would definitely want 5.13s if running any smaller tire.
On the trails mainly run hi range and 1st gear around on the trail heads.

I will try to crawl in 1st and low, but it's pretty useless. Even getting on the loud pedal, the wheel speed just isn't there.

Most of the Time I am able to do almost every obstacle in 2nd gear. Gives me plenty of reduction to crawl and then gets the tires going on the throttle.

For the really nasty stuff, and to bump up places, usually abt 25% of the time on hard trails I will use 3rd gear and usually dump the clutch and get on the throttle. If this doesn't work, I'm pulling cable.

My crawl ratios for 1,2, and 3rd, are 82:1, 50:1, and 31:1. With knowing these, and how these ratios work in our terrain, I would never spend $$$ to get anything lower, and would shoot for 40:1 - 60:1 in the future.

Using a stock d300 gear set I could have ratios of 54:1, 33:1, and 20:1, which would keep me in 1/2 gear on the trails instead of 2/3, but would have saved me $$$.

With all that said, if I were on the west coast where more traction is readily available, or have sticky tires, or a rock bouncer with more HP, I don't think these ratios would apply.
 
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33" and 4.88 was too much gear in my experience for street use.
 
333s and 488s were sporty as hell in my tj short armed with a full traction wishbone rear and no sway bars. Wheelie machine!
 
For me its all too much money for little gain. I have 4.88s with my auto though (and have a set of 35s and 32s that I run) so that may be why I have a slightly different opinion but I just don't see it justifying the cost and the fab work that is needed.
 
Stuntman Autoworks said:
What axle gears do you have now and what were they stock? What's your low range ratio now? What size tires you running now and what size tires on your rig stock?
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Currently I have 4.10 gears, looking to upgrade to 4.88 in the near future, stock was either 3.07 or 3.55. Running 33" TSLs that measure almost 34" now, stock was probably a 30" or a little smaller.

My current crawl ratio is 42.7 (3.83x2.72x4.10)

With 4.88 gears my crawl ratio would be 50.8 (3.83x2.72x4.88)
 
If you think 4.88's are in the future. I wouldn't spend on the t-case until after the axles were done. You may not need it then. If you drive on the street much at all, I would pick my axle gears to suit that and then gear the t-case later (if necessary) to get the low range you want. Like Ron said, I beleive 33's with 4.88 gears may be too low for the street, but thats a decision you have to make based on how much you drive and how many RPM's you want the engine spinning.

FWIW, I had an SM420/dana300 with 4.88 axle gears that gave me around 88:1 low range. Even with 38" tires, I rarely used 1st gear/low-range. I spent most of the time in 1st gear/high-range, or between 2nd and 3rd/low-range. 1st gear/low was great for crawling.
 
I'm with strange1 if your going to 4.88s I wouldn't spend time or money on the tcase. I'm actually surprised you need lower gears I had a couple xjs 4.0 running 33's with 3.55s and never had a problem crawling. But they were all autos so maybe that's the difference.
 
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