Silly noob question. 4 to 1 transfer case?

[Pig-Pen]

ok, new to jeeping here. ive had other 4x4s in the past before but didnt know much beyond the basics. im learning a lot thanks to this forum and the interwebz.

i see people mention the Rubicon has the 4 to 1 transfer case. does that have anything to do with the gearing? or completely separate? if so, what does that mean? what does the sport and sahara have?

ive kicked around the idea of selling my sport for a rubicon though id take a sizeable financial hit. im happy with my sport. i figured down the road i can grab some take off rubi axles and score the gearing and lockers all in one shot. and ill have quick disconnects as well. so i believe the only thing id be lacking is the rubi transfer case?? if anyone really knowledgeable can expand on that it would be appreciated by me and im sure others as well

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[D60]

It's a lower low range. Stock is otherwise 2.72:1

Since chain driven 'cases have come around they've more or less settled on approx 2.7:1 for low range in the wide majority of domestic 4x4's. The gear driven NP205 of the '70s was 2:1 (technically 1.96, and it is BOMBPROOF)

For a couple decades off-highway enthusiasts have been doing things like doublers, basically putting 2 t-cases together to get an increased low range.

Eventually the aftermarket picked up on this with manufacturers like Atlas, but they were THOUSANDS of dollars.

Finally the OEMs are catching on, and it's great. That said, a JL with 2.72:1 is still gonna be fine, but the 4:1 is sooooo nice if you crawl!

 

[Chocolate Thunder]

The 4:1 ratio is the number of times an output shaft rotates in relation to turns of the input shaft. The larger the ratio, the more torque the output shaft has. 4:1 means the output shaft revolves once for every 4 revolutions of the input shaft. This is accomplished by a proportionally higher number of teeth on the output gear. A 12 tooth input gear and a 48 tooth output gear would have a 4:1 ratio.

So it takes more spins of the input shaft to get one revolution of the output shaft in s 4:1 transfer case than a 2:1. This means that the output shaft in the 4:1 turns slower with a given power input, and creates more torque.

That’s not s silly question at all, it’s a very intelligent one. It’s how you learn and understand if you’re new to this.

 

[D60]

Or in simpler terms if you've ever ridden a mountain bike or a "10 speed" your transfer case is the chainrings (at your crank/pedals) - basically a gear splitter for your cassette at the rear wheel which is like your transmission in a vehicle.

edit: the t-case is also responsible for powering the front d/s, but that's not really relevant to this discussion.

 

[jessedacri]

So does the Rubi 4:1 t-case apply to all drivetrain modes, or just when you're down in 4L?

 

[Sean L]

So does the Rubi 4:1 t-case apply to all drivetrain modes, or just when you're down in 4L?

Just in 4LO. 2Hi and 4Hi is a 1:1 ratio.

 

[D60]

So does the Rubi 4:1 t-case apply to all drivetrain modes, or just when you're down in 4L?

Nope, high range is always 1:1. Gear reduction (in the t-case) only happens when you shift to 4L.

Your transmission and differential are always giving you gear reduction (or induction in the case of OD)

Crawl ratio is low range ratio x diff ratio x trans 1st gear

 

[D60]

Incidentally if anyone ever has the opportunity to open up/rebuild a t-case, do it!

They're easy, fun, and you'll learn a LOT. Easy to see how they work once you're in there, including the planetaries (low range) and chain (front output)

 

[jessedacri]

Nope, high range is always 1:1. Gear reduction (in the t-case) only happens when you shift to 4L.

Your transmission and differential are always giving you gear reduction (or induction in the case of OD)

Crawl ratio is low range ratio x diff ratio x trans 1st gear

Got it, thanks for the info! I build scale rock crawlers and get to be hands-on with tiny transmissions, diffs/OD, portals, etc but it doesn't quite translate to the bigger stuff since they're usually set up single-speed for a specific purpose. Excited to get my hands on some of the real deal drivetrain stuff in the future. Pic below is my gateway drug that ultimately has me moving from an Audi to a JL.

 

[D60]

Wow a '78/9 Bronco!

edit: you should probably hang a 100# weight on that to scale the weight. And make it REALLY underpowered to mimic the 351M or 400

 

[D60]

Just to put things in perspective, a real 78/9 Bronco woulda been 2.46 1st gear in a C6, 2:1 low range in either the NP203 or 205, and 3.55 in the diffs. The 351M made a whopping something like 152hp from a V8

So, 2.46x2x3.55 = 17.47:1 crawl ratio

A JL Rubi would be 4.71 first gear, 4:1 low range and 4.10 in the diffs while putting out 285hp from the 3.6. Of course torque curves and powerbands are different from a V8 to a V6, but still you can see which might be better for, well, almost everything

So 4.71x4x4.10 = 77.2:1 crawl ratio

I love old iron but there's a reason it's old sometimes

 

[Therby]

Yes the 4:1 is nice

I have a manual transmission sport with 4.56 gears and 35s

My next big upgrades will be a front locker and a rubicon transfercase

 

[entropy]

Take the difference in price (your financial hit) and customize the sh!t out of your sport. Way better way to spend your money imo! than going rubi. Unless you really want that decal.

 

[donmontalvo]

I bought a set of Dana44s with tru-locks, less than 7K miles, for $3,500, installed them last weekend. The lockers are amazing, though doing tight circles in a parking log might freak you out. They're connected to my sPOD.

One caveat to swapping for Rubicon take-offs is the Jeep might toss up some errors. ABS, Traction Control, 4WD, and Cruise Control, from what I've seen. Jeep told me to bring it in so they can take care of those things.

I agree, the cost of a Rubicon, well, lots of goodies, not necessarily what I would want. Sport S plus mods is IMO a better approach. Buy the platform, build it up, and no worries about removing very expensive parts that you never wanted but paid for. LOL

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