How Jeep 4WD Works

Here's what's inside a Jeep 4WD transfer case and how it works!
A 4WD system is a selectable system where the engine drives all four wheels. It has a low gear range mode for multiplying the engine's torque and a mechanism to lock the front and rear driveshaft speeds. This allows for a very capable vehicle off road since no slippage is mechanically possible between the wheels should they loose traction.
In this video, the transfer case is from a 2018 Jeep Wrangler JL. This transfer case is also capable of an "automatic" mode, or AWD, which uses an electric motor to control the amount of slippage that can occur between front and rear axles. This means the system can be used on dry pavement without binding. This is done with a clutch (bands and friction disks) of which a varying pressure can be applied, controlling the amount of power transferred from the rear wheels to the front (up-to a 50/50 torque split).
The low-gear range is selectable manually through a cable mechanism from inside the cabin. IT has three main modes, hi, low and neutral. In Hi mode, the planetary gearset inside is negated, and the output shaft going to the rear wheels is directly connected to the input shaft of the transfer case. In low mode, the input is attached to the planet carrier, and the output is the sun gear while the ring gear is stationary, providing that 1:2.7 torque multiplication needed for off road use. The neutral state can be used for flat towing.
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[@therealking6202]

This guy's knowledge is first-class. You know in his spare time he's still wrenching on cars.

[@michaelbrinks8089]

I'm somewhat mechanically inclined, fixed all my own motorcycles and diy fixed almost every car issue, installed new engine in my chevy z24 and truck but wish I had the talent some of these youtube resyomod car builders have.

[@therealking6202]

@@michaelbrinks8089 You're WAY more mechanically inclined than I am! I replaced a radiator hose once. 🤣🤣 (Kidding, I've done more, but nothing on your level)

[@michaelbrinks8089]

@@therealking6202 I suck at computer stuff though & couldn't play a guitar to save my life. Also bad with doing math in my without pen & paper. I like working on my own cars but tried working as a mechanic and hated it. In part because not enough knowledge to do things quicker & was always making mistakes when being pushed to replace parts as fast as possible.

[@speedkar99]

Thanks. And yes in my spare time I like working on cars. Mostly breaking them apart though 🤣

[@therealking6202]

@@speedkar99 That's the scariest part of your videos... When you take a part off the engine....but then you open THAT part up and take it apart!!! Putting things back together is my personal hell!!!

[@mattwilliams3456]

Man, thank you for sacrificing part of a unit for this.

[@BlackheartCharlie]

I've seen plenty of engine tear-down videos, but this is the first one I've seen for a transfer case. Great video - thanks for making it.

[@chuckh.2227]

I'm a repair shop supervisor I didn't know a toothbrush had so many other uses I might start carrying one around at work Thanks!

[@muhsalihu]

Do you have access to your brother or wife's own?😂😂😂

[@speedkar99]

Better than the pocket screwdriver eh

[@donvoll2580]

Also to his brother shirt & his wife's too I got to laugh ever time he does video,, They are very good though, Thanks

[@Shadow6a]

That snap ring removal tool, aka grinder, was so precise. 🤣🤣

[@speedkar99]

I love it!!

[@4G12]

Relatively simple and elegant design, not much to go wrong, yet has excellent performance potential. Use of an electric motor to control clutch lockup was a brilliant move, much simpler and more efficient, even less to go wrong, and if it does break, relatively simple to fix. If tuned correctly, you can basically get an ACD (Active Center Differential) in a transfer case actually meant for serious off roading, with a proper low range. Lock the clutch hard enough and the result is practically locked diff since there'll be practically zero slip and zero clutch wear.

[@michaelstrongbow2336]

The cold weather has a 100% effect on power tool batteries. I love your channel.

[@speedkar99]

Thanks...and yes I agree

[@billrowan1957]

I give you props for your knowledge and that you freely share it, but your brother gets mad props for the usage he get out of those tooth brushes!

[@nobatteriesincluded3968]

Amazing to see the inner workings of a transmission complex but interesting great content 💯

[@speedkar99]

I'm glad you learned something

[@JohnDoe-gj4dv]

Sir, Thank you for your VIDEOS.....!!! Your ORATION of this Subject is beyond reproach. You make this INFORMATION comprehendable for the Layman. Please keep the message and mission coming.

[@monkeseeaction21987]

This is awesome. I like how they reduce power loss by using an electric motor for the clutch rather than hydraulic pressure.

[@speedkar99]

I prefer the electric motor too

[@markwilliams2620]

Brings back ancient memories of the adult ed trans/brake course I took in '86. Big change from TH400 and Mincie 4 speeds. Still do my own brakes. When I took the Sonata in for the recall on the "security upgrade" (It's a sticker) they tried selling me a trans flush and brake fluid flush. "Did it last year". "You flushed your brake fluid?!". "It's SW Floriduh, man, you need to every 3 years". My girlie tech was mildly impressed 😁.

[@speedkar99]

Awesome

[@JasonLuther1]

You're the best automotive mechanical engineering feller on KZbin. Great job man

[@speedkar99]

Thanks

[@denniselenson560]

I loved my Jeep, some clever engineering goin on in that car, and yes, that purple oil is very special and very very expensive. The snapring tool never gets old, great video!

[@speedkar99]

Thanks. Is the royal purple from factory?

[@denniselenson560]

@@speedkar99 It was a long time ago, but yes, it looks factory, I remember the original Mopar synthetic oil that was specified as factory had this funny color, the one I drained out and replaced was dark matter black from abuse, probably got stuck in snow or something :)

[@jannehokkanen8175]

you can use normal atf. unless u wanna give extra support to factory owners.

[@grob25]

I took apart a NP205 or 203. It was off a HMMWV. Pretty solid chunk of metal.

[@speedkar99]

Awesome

[@blingbling2225]

This man needs a toothbrush sponsorship

[@speedkar99]

You think I should phase out the toothbrush?

[@blingbling2225]

@@speedkar99 nah man it's definitely your signature lol

[@JasonLuther1]

​@@speedkar99you should get some toothbrushes with your channel printed on them. I'd buy one lol.

[@bytorsnowdog5885]

Entertaining and informative as always!

[@ThunderbirdRocket]

Thorough !! Awesome !!! Thanks ! 👊🏼

[@speedkar99]

You are welcome

[@qkhalili]

Great video as usual, this could help you diagnose a problem much better. Thanks.

[@speedkar99]

You are welcome. And yes learning how something works is the first step of diagnosis

[@KO-pk7df]

Thanks for doing this kind of video, it explains so much of what I really want to know about how this works. That info is out there on the web but it's so weak it's useless. Before buying or working on a Modern Jeep this is so helpful!

[@stger2384]

I never expected it to be so huge! And what a chain! :D

[@speedkar99]

It's a Jeep after all! I have a Subaru AWD I'm gonna tear into next...we can see the difference

[@Dani_RdM]

That's what she said!

[@mtnslyr]

Hey, I’d like to request a quick video dismantling slip joints and spider yoke of drive shaft.

[@markharris6171]

Great video. Like to see a tear down of the NP231.

[@facundonu]

best mechanics youtube channel by far!

[@speedkar99]

Thanks. I'm not a mechanic.

[@adey88splace]

Fascinating video, thank you.

[@speedkar99]

You are welcome

[@repairman22]

Great Video!! Very interesting!!

[@rwriters]

Would love to see you take apart a transfer case from a 4x4. I mean an old school part time 4x4 with an H2, H4 and a L4, like an old LandCruiser!

[@deepbludreams]

That's what that is, chain driven transfer cases have not changed in half a century atleast, they just get bigger. A gear driven version of this is the same just with two transfer gears between the outputs

[@rwriters]

@@deepbludreamsso no clutch, right?

[@speedkar99]

Part time four wheel drive Would be awesome.

[@rwriters]

@@speedkar99 yes please! and add the manual and automatic locking hubs too

[@BorisZech]

Amazing content. Is this setup more like the Quadra-Drive II or the Quadra-Trac II 4WD system of the Grand Cherokee (WK2)?

[@jay26]

Nice video as always. Hope we can get a video on subaru AWD.

[@speedkar99]

Coming soon!

[@personalaccount1515]

I love this channel!

[@speedkar99]

Me too

[@STONEDay]

Take the tool battery apart. Look up the part number for the cells inside. Then find the data-sheet. It will give you temperature performance curves. 😆

[@jbstepchild]

Nothing new to see here but I didn't get dirty that's was worth an like an a sub great job didn't smell a thing

[@milesredgate4596]

Fantastic as always. I would love to see you take apart a Subaru transmission, as from what I just briefly read, it contains both diffs and the transfer case all inside the transmission. I'd be curious to see how different it is from a regular transmission and something with a 4wd setup like in this video.

[@speedkar99]

Yep. I got a Subaru Outback waiting here that tim gonna be tearing into soon!

[@dittrichc]

Thank you for the video, mate! Any chance of tearing down a Mitsubishi 4G94 one of these days? 😃

[@richardcasey4439]

I have a Jeep so this was super interesting

[@u2ooberboober]

Good video!!

[@speedkar99]

Thanks

[@avahrintmurth1159]

Nice video 👍

[@speedkar99]

Thanks

[@billynomates920]

i actually understood all that for once! 😃

[@michaelbezoski3096]

Cold will not affect lithium batteries in the impact wrench (I have same M-12/18 tools), "but" where I worked before retiring (old chemical plant, south shore of Lake Erie), some batteries seemed to prefer the shop over the field when it was below 20f. Funny to see snow as its August 1st. Wonder if that portrays whats to come next couple of years. 🤔 Outstanding video as always!

[@speedkar99]

I find the cold affects the batteries on my tools significantly now that it's summer. This video was shot way back in winter lol

[@jocko_]

Not a Jeep fan but all of this looks well made.

[@deepbludreams]

Transfer cases are one of the few "bullet proof" parts on jeeps, actually managing to break this is difficult, you'll snap your drive shafs before your chains

[@speedkar99]

Its not bad at all

[@imfloridano5448]

This must have been recorded months prior cause that snow could be used here in the DFW TX area with the over 100°f temps. It will cool it down a couple degree's. Thanks for uploading at an appropriate tyme🌞

[@speedkar99]

Yep. Makes me appreciate the weather I have now

[@davejones290]

Thanks for that,

[@speedkar99]

Welcome

[@mohammadrifqisatriamas7311]

wow never thought going to snow in summer

[@speedkar99]

Who said it's snowing 🙂

[@michaelbrinks8089]

I really miss my 92 4dr 4wd slighly lifted Chevy Blazer. It was actually decent built with above average reliability. With some good all terrain tires in 4wd I could drive through 6 inches of snow on city streets almost like there was no snow on the ground. Cars would be going 15mph in a 40. I'd be going 45mph weaving through traffic. Just gotta give yourself extra stopping room. If I still had it, I'd love to make a pop-up roof on it and do vanlife/travel.

[@speedkar99]

Ah yes...I remember my cousin's 93 blazer when I was a kid. Good old days

[@joebaucom4537]

Great !

[@lernmor2137]

For your batteries, it is best to keep them inside when your tools are not in use at room temperature, which is about 70 degrees or so. The batteries slightly heat up and will remain warm as you use them. There are videos on YT as to how to open those battery packs up, test each individual battery in there, and then replace them if necessary.

[@jonesliuquan]

10:30That clutch looks like one on my old Honda CB400 REVO XD

[@Cristobal_Ygnacio_Arriaga]

I wonder how this compares to a full-time 4WD system like my Fj Cruiser. The manual Fj has a torsen differential in the transfer case. It gives you 4 options: H4. H4-lock. Neutral. L4-lock. No electric motor just the lever inside.

[@speedkar99]

The lever likely controls the locking up of the clutch, just like the electric motor has.

[@EnergySeeker]

amazing as usual thank you

[@speedkar99]

You are welcome

[@user-nn6sq8ow5g]

Hey Speedkar99, any chance you can do a mechanical review of the recent 2020-2022 Lexus RX hybrid please? They're really common cars, so it shouldn't be too hard to get a hold of. Thanks!

[@Thekidsinafrica14]

The cold weather? Where you live at? I’m trying to get some of that😂

[@mugenlee8276]

So ...how long the inner chain last ?

[@sornewp]

what is the partnumber of the trans case ?

[@doctor_who1]

can you do a teardown of X Drive RWD AWD system

[@speedkar99]

Sure. Send me the car 🤣

[@klauscottonswab2322]

Is it snowing there?? Lol I always wonder what you do with all the parts.. ??

[@Enigmaafk]

Nice 😊

[@speedkar99]

Thanks

[@KevinMiller-lh9ur]

Cold definitely affects batteries but it’s still summer in MD. No cold here. 😂

[@speedkar99]

No cold here either. Video was shot way back in winter and old got around to editing it now.

[@Walkeranz]

Nice snap ring tool 😅

[@Aleks_Mechanics]

Notification SQUAD!!🔥🔥🔥

[@speedkar99]

Awesome thanks

[@rdallas81]

T 34 tank with v 2 engine used the 3 bearings on a plate to activate the clutch also. 1930s technology Soviet Union.

[@tanawatkrubb]

'snap ring remover tool' LOL

[@maksymiliangruisen4944]

What do you do with all the engine and transmission parts after you disassemble them? Do you sell them or just let them sit somewhere in your garage?

[@speedkar99]

Scrap

[@vivi_75]

Yay a speedkar vid

[@speedkar99]

Yay!

[@LeavingCaladan]

hey speedkar, were/are you an automotive tech? or engineer? and what do you do now?

[@victorwilks88]

We want merch !! 😮

[@speedkar99]

Isn't there a link in the description?

[@johnharrisjr.351]

Yes, to everything that’s happening here… Yes!

[@speedkar99]

Yes

[@noahwyatt9260]

Hey man where do you get all your engines and transmissions from you have fun with? Id like to break into some stuff to learn for fun aswell.

[@speedkar99]

Marketplace... people selling swapped engine cores , or I just buy the whole car and part it out!

[@canadatransistor]

that's a pretty smart pair of pants to go along with the smart toothbrush! #Smartypants

[@olspanner]

Battery seems fine to me, you're as fast as ever! lol

[@speedkar99]

Nah it just couldn't cut it in the cold. Now that it's summer I definitely notice me not running to change batteries as frequently

[@nickchannel5364]

It's hilarious that you take your family ’s clothes to use for shop rags. It makes your channel stand out from the rest.

[@speedkar99]

Haha Stand out Lol

[@buddyrojek9417]

Chains stretch , big problem in second hand jeeps. In my opinion get diff locks without a chain system for all wheel driving

[@RM-pi4sh]

13:51 what is that...? Any one know this much of coil is for????

[@DM-hw4cr]

That transfer case is known to burn out from running unevenly worn tires!

[@speedkar99]

That's if it's a part wheel drive system without a clutch in fluid.

[@hedydd2]

How did you find cold weather at the end of July?

[@speedkar99]

Editing this now was a reminder to enjoy the weather I have now.

[@ike2010]

Would like to see the BMW xDrive system in comparison

[@speedkar99]

Me too

[@FrankyRedEyes]

Question. Is your brother missing a transfer case?

[@calixtoemilio]

Having this problem. 2WD is not working, there is a weird noise, even in P. But if I switch to 4WD, vehicle moves "normally" (can promise will do in the long term) and no weird sounds. What could trigger that?

[@speedkar99]

It should be backwards As you see here, power is always sent to the rear wheels...

[@calixtoemilio]

⁠@@speedkar99, that is what triggers my curiosity. Makes sense that 4wd is moving front wheels only? Or that linkage selector is not going exactly to 2wd?

[@calixtoemilio]

clarification: the cranky noise is in "D" and "R", not in "P". Found another curiosity. In 4WD, switch to "R", open the door and autoparking gets enabled , "R" flashes and the rear shaft stop spinning, in 2WD, open the door, autoparking is not engaged , and rear shaft keeps spinning (emergency brake applied) Sorry for the inconvenience. I am in Babb, MT, nothing near to help, will tow the jeep with my RV to a next location with some local facilities available, including a couple of Jeep Dealers. Just trying to satisfy my curiosity.

[@timtim8468]

I'd like to see a visco clutch. The old Volkswagen had them, people are crazy about getting Bulli - 4WDs, when it's actually a cheap a** solution, like the small Suzuki use today. My point, 4WDs come on different levels.

[@speedkar99]

I have another video on the G35 AWD. That one uses electromagnetic

[@jamsbong]

I prefer the full time AWD of the Audi Quattro because it is fully mechanical.

[@speedkar99]

I'm gonna see what symmetrical Subaru has too, I've got a transmission next on the list for teardown.

[@sudheeshalakkal2462]

Good information bro.... studying ❤

[@speedkar99]

Thanks

[@DaDaDo661]

Cold weather? Its summer bro where are you ?

[@speedkar99]

Living in the past winter still

[@thatoneotherotherguy]

It sounds like this is a "full time 4WD" setup, which for 2018 probably would've only been on a Sahara-trim Wrangler? Would be nice to see how simple the more traditional "part time 4WD" is on JL's. I would think that the part-time only transfer case doesn't have computer controlled components? There's no variable torque split in those--when you put it in 4hi or 4lo, you're getting 50/50 front/rear power split, period.

[@speedkar99]

Yes. I mentioned this further down in the video. Older models just have the collar engaging and disengaging the 4WD. Would be cool to open one of those some day.

[@thatoneotherotherguy]

@@speedkar99 not even older models, just many of the current models. To my knowledge, a Sahara gets full-time 4WD as standard, and you can optionally get it in a Rubicon. Other models just get the traditional part-time 4WD. My buddy just picked up a 2024 Wrangler Sport. Has part-time 4WD, but really wild is the manual windows.

[@Wiggywom]

​@thatoneotherotherguy I went with manual windows, too many trucks of mine have lost all windows due to switch failure.. (they ain't cheap either) and once an AC fails here in south texas you won't survive the heat inside.

[@SirajKhan-pt5rc]

👍👍

[@mikekokomomike]

You were referring to flat towing with all 4 wheels on the ground. I learned you shouldn't tow a Jeep with the back wheels on the ground even if you have the transfer case in neutral.

[@omegarugal9283]

depends on the model, check the manual or if the tcase case says N-tow then you can. for long distance towing just remove the axles to be sure

[@mikekokomomike]

@@omegarugal9283 thanks, I figured there were exceptions. I found out that some you can't, brother in law has a JK Rubicon

[@javieracevedo9352]

That trannie looks like a 42rle, same one my Jeep Liberty has

[@speedkar99]

850re. See my other teardown video on it

[@user-dm4yv1wl8h]

watch model

[@EIRK2046Y]

the chain is the weakest point of the distributor

[@speedkar99]

Clutch

[@n5sdm]

As a mechanic that has years of experiance working on jeeps and as a certified elevatortechnician. Do not ever touch my vehicle!

[@speedkar99]

I'm good at breaking stuff. Not very good ay fixing stuff 🤣

[@n5sdm]

@speedkar99 spent my life fixing others fixes. 😆

[@fjb4932]

n5sdm, Deal. Fix it yourself. ☆

[@glock18supercharger]

😊✌️

[@JamesLee-oe7mt]

It's cold somewhere?

[@speedkar99]

A few months ago ha

[@rinse3x]

U should do some diesels

[@speedkar99]

Ok

[@cernejr]

2018 Jeep and already getting scrapped?

[@speedkar99]

What to do...

[@kelvinjaphet]

veiwer no 1😚😚😚😚😚😚

[@speedkar99]

Thanks

[@JohnSmith-sh1zg]

8 speed not a 6 speed.

[@javieracevedo9352]

The 3.6 pentastar is famous for being bad.

[@speedkar99]

Check out my other video on that Pentastar

[@estudiom142]

[@JCVACCARO]

On the Jeeps with quadradrive 2 you must replace all 4 tires. If you replace only 2 or have 2 different sizes it will destroy the clutches in the transfer case. If all tires aren't the same height the computer will think there is slippage and be constantly engaging the clutches. How do I know this? I personally blew one up by getting 2 tires instead of 4. Whoops. It is in the manual. Spread the expensive words.

[@speedkar99]

Ouch!

[@speedkar99]

How much did it cost?

[@JCVACCARO]

@@speedkar99 3600$ 6yrs ago

[@JasonLuther1]

Yes sir, same with any awd setup. Sometimes we learn things the hard way

[@alexkram]

​@@JasonLuther1there are different types of AWD systems with different pros and cons. My '98 Jeep Grand Cherokee has a NP242 transfer case with a center differential when in AWD mode. Different sizes wheels won't hurt it and there are no clutches to wear out. It sounds bad to have an open center diff off road because if one tire loses traction, the other 3 lose torque. However I have found it works extremely well and only rarely need to use the part time 4WD mode that locks the center diff. Works especially well on snow and slippery gravel roads.

[@kclefthanded427]

Batteries won't do well in cold weather, just like EVs even with a heater pump

[@speedkar99]

Sadly.

[@LankaRohithkumar-ge5sj]

Hi bro language problem telugu videos kavale bro

[@nigelalderman9178]

Ha ha, the ball bearing balls engaging and disengaging the clutch is the same idea as a Russian T34 tank . See 7.03 to 8.35 kzbin.info/www/bejne/gYLSgZimi6-lsLM

[@speedkar99]

Nice