Fitting 40's on a TJ, What you need to know before going 40's! 

I’ve comfortably ran 37’s on a D30/44 with spacers for the jk bolt pattern and extra clearance combo with 4:88 gears and Cromo axles , tube fenders and lock right lockers front and rear. The gears are plenty deep enough . The real factor here is how you drive! Every video here of him driving he’s full throttle,smashing over everything. He’s going to break everything eventually.

Thank you! I’m sure you know how much research you saved me, but wow I got to tell you anyway! Hours and hours upon days! Thank you for the chart! I’m sure it was challenging! I know exactly what to buy, and you potentially saved me thousands,

Awesome info on the tire sizes, gears and axles. Very helpful video overall.

Years ago I rocked a K5 Blazer with built D44 in the front with 40s on it. It never let me down

Good job, brother. Charts and info are where its at!

I have 35” tires with 4.10 gears on my TJ, but then again I also swapped in a 5.2 magnum V8. Great info!!

That was a great chart and so much depends on the type of terrain and how you wheel. I ran 36 Bias Iroks on a Tj Dana 30 with chromo axles and a lockright for years but the terrain was fairly mild and I preferred to crawl.

good job , lots of usefull information . thanks for your research .

Currently have a 92 YJ with Dana 30/35 with chromoly shafts and 4.88 Yukon gears with the 2.5l 4cylinder and 37x13.5R17 with Kmc bead locks , never have given me an issue on the road or off-road, always use to think you need a bigger motor and diffs, but realistically the budget could only go so much, have ran this set up for over 2 years now and still going strong and can cruise comfortably and not such a dog, eventually will upgrade the diffs when the budget can open up more, but don’t believe in trying out something just because everyone seems to be an expert! Try it first and have a mental note that yes things can happen but also don’t believe what everyone says !

For me 33” and 5 speed manual on stock gearing I have abselutly no issues rock crawling in the Texas hill country. No i can’t do big 8 foot ledges but otherwise I send it with the stretched big boys

Nice video man! I dig the chart. A bunch of great info! I never had luck with my dana 30. 35's and a lunch box locker took out a couple axle shafts... but I never upgraded to chromoly shafts.

Dude these are awesome. Keep up the channel!

Love the video man! I’m building a 1 ton TJ on my channel now and appreciate the pointers!!

Your chart was very impressive. So many ppl have opinions on what and how to run tires with specific set ups. My opinion was different to yours, but I like everything you said, and you have actually made me lean more to 4.88s than 4.56s now 👍🏻

Thanks Kelly, very helpful 👍🏼

I agree anything over 35 inch tires will not work witout lockers , i’ve sooo many jeeps can’t get over a rock with 37’s and no locker where the jeep on 35’s had no issues at all . Nice video man 👍

Thanks Kelly!!! Very helpful. I know 40s are the craz right now but as of now 38s are the largest I’d go and there so many upgrades to get there...lol!!!

I'm running 38's on trussed and supered D30/35 with 4.88's and ARB's. I've definitely seen videos taken by friends where I'm crawling over some obstacles and you can see my driveshaft rotate significantly before the wheel does. Putting some major torsion on those axle shafts before they spin the tires. Also running the WJ swap up front with Barnes steering kit for the WJ knuckles

running a '76 chevy dana 44 in the front of my TJ with a v8 and dual cases with 40 TSL's. stock 4.10 ring/pinion w/ grizzly locker and havent broke anything in the 6 years i've had it that way running a '78 ford hp dana 44 in the front of my solid axle 4 door tahoe on 37s. stock 4.10 ring/pinion w/ grizzly locker and grenaded both front shafts ears/joints pretty quick! weight of the vehicle matters for sho!

Imagine that. You narrowed your front axle then had to put wheel spacers on it lol

Check out Jake Burkey's 4 link build and how to make the perfect 4 link for off road. He has it written on a white board like you but he also has the recommended length for tire size.

Sick red TJ! 40s look epic

You can add a few washers on the steering stops to keep the tires our of the control arms.

'89 Renix 4.0 2dr XJ, AW4 (Full manual with RADesigns rail shifter) stacked 231/231 transfercases- 6 pinion and wide chain in main box, built D30 (sleeved, gusseted, Grizzly Locker, 4.56, OTK steering, etc), 8.8 rear w/super 88 kit (trussed, full spool, disk breaks). A lil over 94:1 final ratio in compound low. I run 34/9.50 TSLs (soon to be Q78 TSLs) for summer trail riding & 38/12.50 (heavily cut and siped) TSLs for snow wheelin. Agree that the D30 ain't big enough when you've got good traction with big tires but it works out great when floating on deep snow (or sand too). A light throttle foot in the rocks with the Grizz up front saves shafts but I'd still like to go with RCVs- anybody wanna give me a set???

I have a 2010 JK with 35's, and was considering getting 4.56 gears. I think you talked me into it, I'll get 4.88's. Cheers from Canada.

I've got a little 99 tj I have a dana 30 front and 40 rear I run 4.56 on 33s, its a perfect little crawler, it will absolutely take me anywhere I want to go on my little 2.5l 4 cylinder, I want to bump it up to 1 tons 40s on an ls, that'll take some time and money...

Nice i did that on my ZJ about a year ago extend the bumpstop and work very good , I like what you say doing upgrade one at the time im not reach , that is me be safe out there .

Great video, but you forgot about gear ratios compared to your transmission. What kind of transmission you have, and what it’s gear ratios are, speeds , and overdrive if your on the freeway, is a more important factor to choosing differential gear ratios for your specific tire size and ultimate plans for your jeep.

You don’t need wheel spacers if you get wheels with different backspacing. However.. it’s much easier and more common to just use full width axles and adjust the backspacing to bring the wheels in as much as possible for good scrub radius. Also not sure you’re aware but you didn’t need to narrow the front.. there are full width 8.8 axles. They are easiest to find from f150’s. They come with drums instead of discs but have a wms if 65.5” and would’ve paired up with the 76 d44 in the front. It’s not a common axle and can usually be had for $200 or so in decent shape. I used one on my last tj I had. Would’ve been a way easier route to swap that then to narrow the front. It’s been a while but I think it’s the early mid 90’s trucks that had them. Same ones that had that weird split 44 in the front. Like everyone else I wanted that nice 44/9” doner but finding a 9” to pull is like panning for good. The 8.8 is plenty of axel for anything other then the new JK,JL unlimiteds which are closer to a Land Rover in size and weight then a Jeep. As for 241OR transfers.. you can find them on eBay around the $7-800 mark from time to time. That’s the way I’d go as they are way way stronger then the 231 and stronger then a Jeep will ever need at 7500 ft/lbs if torque rating. Which is almost double that of a 231. A great option is the GM h1 242 if you want to swap the trans too. A lot of gym autos will bolt right up to the 4.0HO 700R4 being the one I’d choose since they are strong and cheap to work on and can about the most easy to find junk yard pull there is. Not a lot know about the h1 242HD but it’s to the 242 what the 241 is to the 231. That full time limited skip 4wd would be fun to play with at times. Sadly the regular 242 just doesn’t work with big tires and low gears as the limited skip clutches just burn up. And aftermarket support for the 242 still sucks. Twin sticks are cool an all.. but for the cost of an atlas I can swap everything from the rear axles to the flywheel for the same cost lol. I’m actually really surprised more people don’t do Chevy trans to 241DH swaps. Especially manual jeeps. Sticks are fun and all till your on a 30-40* climb. Not sure I’ll get around to building another tj anytime soon but I would run 4.0, 700r4, np242HD, full width 8.8, full width 44 to run stickies at 40”. That’s about 1000-1200 total drive train before building for a bulletproof light rig. If I ever figure out how to fit 40’s on my current xj project while retaining most of the Cherokee body that is still the route I’ll take. But likely gonna be stuck with 36-37 depending on the final tire width I decide. Last thing.. you list 4.88 as the smallest 36-37? Yet have 5:13 with 40’s lol. That’s not even comparable to 37’s in 4:56’s when you factor in the weight differences? Your ratios don’t make a lot of sense tbh. They seem to only be accounting for size and not weight which after 36ish real inches (so 35-37 depending on actual sizing) starts to go up very fast. I’ve run 37’s in 4:56 with both 2.72 and 4.1 and both autos and that German 6speed and never felt like I needed lower gears. Hell my 06 TJ with 39.5” tires 2.72 and 6 speed I could literally bunny hop the Jeep on pavement it had so much torque. (All 4’tires off the ground) was a bit of pain to load the suspension properly but was a cool trick that got lots of attention lol. 4.88 are the step child of ratios.. I personally stick to 4.56 unless I’m going to run tons at which point 5:13 becomes the min. But I wouldn’t run 5:13’s in a 44 any more then I would run 4.88’s in a 30. You are just putting your weakest link in the hardest to get to area to repair on a trail doing that. I’d rather snap a outer or something else before shattering a pinion.

I running 35 with 456 gears a Dana 44 front ARB and Dana 60 rear ARB I’m very happy with my setup

That’s kind of depending on what engine you Are pushing I got a super 60 front 8 1/4 rear with Detroit locker Eaton rear and the front grizzly I’m running 40s with a 410 gear ratio with a 302 engine

I have a late 70’s high steer conversion Dana 44 front and a 9” rear - eventually I want to run 40’s

1994 ford explorer 4.0/5speed , hp44(narrowed EB width)/8.8 4.88 gears spartan lockers, chromos, 38.5/15.5 grooved boggers, Atlas 5:1 2 speed. works really good in the snow, but eventually wanna move to probably just 37s. need to switch out of radius arms eventually too.

I love this jeep

4.88 gears are awesome with the 35s on my TJ, so spunky on and offroad. Even made the crawl ratio better compared to the stock 3.73 gears too.

Ford 9 inch has been one of my favorite axels. We ran them in race cars offroad rigs and a couple of backyard rock buggies that were the best all around rigs i ever played in. One thing i have learnd over the years is build a lite weight rig. Weight is a key factor. I wish the Cherokee had a real frame under it . So a guy could remove the body and turn it into a rock buggy. You could lose 2000 pounds of body weight and i could run 40s on a built stock axel. Bronco 2s work great for this project with 36s. I always wanted to do this to a TJ . Yea 40s

How to run 40s on a jeep. Step one change entire drive train. Lol

I'm running 35" bfg km2s on my tj dana 30 4.88 gears and 8.8

Great video, just subscribed.

Good video. I'm surprised no one talks about Auto vs Manual when making axle gear ratio recommendations.

Nice Vid! Just clearing up a few things on the tcase gear selection. The Dana 20 low gear set is only a 3.15 ratio. If going to a Dana 300 in a TJ with a stock driver drop going to need to do a flip kit on the 300. Im currently running a Dana 30/4.56/chromos front and Super 35(30 spline chromo) Dana 35/4.56. Both ARB lockers on 35's. Its been a very reliable set up. Been over the Rubicon/Fordyce/Barrett multiple times no issues. I just picked up some Solid Industries HP60's F/R and am debating on tires. I love driving the Jeep to work and to the trail so thinking 37's but want 40's!!! The tcase is an Atlas 5.0.

Definitely a ‘Shot Caller’ !! Great chart concerning axles and gear ratios. Picking up a HP front axle assembly this weekend for my Jeep. Good video Kelly! ❤️🐞

I recommend that if you're gonna run 40s or bigger, you and you can find some portal axles. You will see a much greater ground clearance improvement. 40" tires compared to the stock 29 inch tires gives you 5.5" roughly of ground clearance improvement from the ground to the axle at any point. with portal axles you can gain a rough estimate of 3" of additional ground clearance while also increasing the room for up travel by approximately the same amount. Another thing to consider is that the gas 4.0 L6 and further more the 2.5 l4 start to get a little underwhelming on larger tires, and i would highly recommend either turbo charging or supercharging the 4.0 or swapping with an engine you can get a bit more torque out of. like a 5.3 LS (cause they're cheap) or a mercedes or VW diesel engine... And the beefed up 1.9 TDI engines have been known to make 3-400 ft-lbs of torque... From the factory the 2006 tdi engine for the beetle and golf makes 177 ft lbs at 1800 rpm

Could you use a wheel with different backspacing to eliminate the wheel spacers, tire rub?

I got Procomp tires as well and I love them. How much did the tires and wheels cost you if you don't mind me asking? I

I'll be $3500 into my hp30 and 8.8 from sff customs. Just getting them painted up and ready to put in. I don't have the means to weld so it made more sense to have them built. D30 got an ox locker and a truss. 8.8 got new lsd clutches. Both got new 4.88 gears and seals.

I'm learning a lot from your info for tires and gearing, can you guide me build my jeep, and how to start my project?

6:25 good info

Great video no BS! I think you forgot the chrisler 8.25" 27spline rear?=dana44 rear and way easier to find. Good to around 35" The usual suspects are going for too much money if, you can find one😒. Yes you have to put brackets ECT. But you'll probably do something like that anyways. Food for thought...

What do you think of upgrading a Dana 35 with 4.88 gear Ratio and having 35's tires ? Still cosider it as crap?

You've probably answered this before but what flat fenders are you running? Great videos btw.

Kelly- “I’ve broken more dana 44 stuff than i have dana 30 stuff.” Nate from DL- “I’ve broken more dana 44 stuff than i have dana 30 stuff.”

You rec 4.56 for 33's and 4.88's for 35's. I run 35's on a 5spd with the 4.0L. By my own admission I'm a mall crawler. Lolz. But would like to re-gear for the road. What gears would you rec for road use? We have some freeways here in SoCal with 75mph speed limits where drivers reg go 85-90. I don't plan on doing that but I often have to downshift to 4th just to maintain 65 (actual) going up a 3% grade.

Not a fan of wheel spacers. Did you consider wheels with a different off-set? No changes to the steering box, bracing, etc... Gotta love a RED Jeep! :D

" Dana 35? No one wants that garbage" Amen to that brother hahaha

Good video but a lot of people run Aussie and loc rites etc with big tires and although pointless in my opinion they work fine until they break lol never seen issues with them not locking up

One question... In that cutaway where you cut to some desert trail footage, was that trail Isham Cyn in Trona or was it somewhere in Johnson Valley?

In my JKU with 3.8l auto i ran 37's on rubicon axles, rear stock, front was sleeved gusseted and ran rcv axle shafts. It was ge a geared 5.38's. It needed a v8 swap still. And the 5,38's did not last. The gears were installed by a tech and it was taken to another shop to see if it was done correctly. The pattern was good. It still failed. Pinion on a 538 is to small IMHO. 5.13 should be as deep as you go with jk rubi axles and you need a v8. I agree full width axles are needed for 40's to clear. I am building an LJ with 1 ton axles in mind for large gear strength and for tires to clear the frame. Beefier assemblies and bigger brakes is a bonus.

I have a Jeep TJ 4.0 I6 1997 manual 5 speed with front axle automatic (Aussie) locker on Dana 30, rear axle Yukon DS73630 POSI LSD locker on Dana 44, 9,500 lbs. winch, tow package, 2.5” lift, KO2 31” tires; factory gears 3.07s. It’s not a daily driver, but I go drive 80% paved roads 20% off road, mostly on trails ATV go. I’m thinking of going 31” or 32” KM3 tires. Should I re-gear?

Just wondering if your gear recommendation for tire size is specific to a 231 T case with 2.7 reduction? I’m installing 4.56 gears with 33’s and plan to upgrade to 35’s but I have a Rubicon with nv241or with 4.1 reduction. Will this be good?

i saw yellow jacket at tahuya

Just bought some used axles. need to re-gear them. I have 35" tires waiting to go on but I'm wanting to go bigger as soon as possible(could be a while depending on funds). Looks like I could go 5.13 gears and be good for 36-40's would it be stupid to run 5.13 for now with 35s?

hey so question, what about the G2 core 44s for the TJ, the front has 30 spline outers, and both have chromoly shafts, what size tires would you run with a set of them ?

Bad advice at 4:36. Wheel spacers alter the Ackerman angle on the axle. A properly designed axle housing to fit the vehicle’s build and intended specs would have been the right approach. But then again, 40’s on stock wheelbase advise....

Did anyone else mention the Terralow 4:1 kit for the np231j ? I'm running it with d60 14b 5.38s and i have all the gear i need with 38.5 swampers. Drag 7000 lbs shipping container on dirt.

You said your running a spool up front? Is that hard to steer? Im going to build up my d30 in the front im going 35’s on my Cherokee. I did get an 8.8 from the junkyard and will truss and 488 gears. I guess my question im trying to figure out im going Detroit in the rear don’t know up front would Detroit work in front just worried about steering on, stock steering box

Need help vibration over 55 and over not death wobble any ideas tires also being balanced and rotated and in line with each other help

How much stretch do you have? I want to go 40s but I am kind of afraid that I will be too high with not enough wheel base. I am not stretched at all as of now with a 6" Rubicon Express long arm suspension running 37s. Wondered if you had stretch or not? I see that you have outboarded your rear shocks.

I saw guy on RU-vid that had a Cherokee with bogger 40's on a Dana 30 and 35 lol

I have plans to build another jeep, but right now I'm building my '06 2wd Chevy Silverado Prerunner . I am having trouble finding dana 60 here in Ohio between Cincinnati and Dayton. Do you have any good hookups for old axles?

Flip this front shocks over boss :) Helps keep the dirt out of them

"You've lost that rubbin' feeling ". Now It's gone, gone, gone.

What is the locking hubs for I don’t understand?

i’m running front dana 30 with truss c gussets chomemolly shafts and 5.13 yukon gears on 17s with 38 patagonia milestars . i do light wheeling. am i ok or am i pushing my luck?

Currently I’m running a hp 30 and 8.8 both locked. Taking front axle shafts all the time on 35s so I’m putting in chromoly shafts next week hopefully that helps. Also working on building jk 44 axles for it. That should help with the width issue. Great vid👍

I have a tj with 6.2l and 6l80 on 37s - what ring and pinion would you recommend?

I have an 05 Rubicon, stock gears with 35s. I may go to 37s or maybe not, not sure yet. Would you go with 488 or 513? If I would go to 37s it would be a couple years. Thanks for any advice.

Can I run 4.88 gears with only 33’s?

Have you streched the axels?

Asking for a friend. Will this work on a 2.5?

I run 37 x 12.5 on Toyota Hilux axles in my YJ with 4.11's. Spooled in the rear, Aussie lunchbox up front, with a 2wd Tera Low kit. I have zero HP or torque issues with the stock 4.0L/AX-15. Could it be geared lower? Maybe, but for me it works, and I would tell any newbie that wanted to run bigger tires, but couldn't afford new gears right away, to just go ahead and put the tires on...

🔥🔥🔥

new to the gear ratio changes. why do you suggest 4.88's on a 35" tire. if this is a daily driver would a different ratio make more sense? gas mileage, rpm's, age of vehicle (01 wj 4.0 with a 42re trans). not looking to go full on rock crawler just be able to go have fun.

You said you wanted to step up tp 5.38's. I have a 8.8 and wanted to go with 5.38's but I can't find any. They go up to 5.13 and then jumps up to 5.71's, have you found 5.38's for your 8.8?

I am just about sold on the Currie 44 ,for the front , and Currie 60 for the back of my 99 TJ with the 4.0 straight 6 . You sound like you're experienced and This is my first time building a TJ . Please be gentle, what are your thoughts? Btw,I'm in Pensacola, Florida, but I plan to travel to the rock county. So I'll be on the road , and carrying rock crawler tires in a tow behind trailer.

Nice video, Thank you for taking the time to do a tire size to gear ratio chart.

Are you running a semi or full float rear? I’m running 38’s on built rubicon jk axles. In your opinion would you run 40’s on a semi float axle? I believe Nate does.

I personally say skip the 35. 8.8s and 8.25s are everywhere and not shit.

Hey i know that guy in the tye dye.

Are your gear recommendations for a manual or automatic? Would 4.88 still be the best ratio for an auto tj on 35's?

40s on corporate 10 bold with chromaly and a 9in under an 86 K5

U make me wonder about my 35s on the rear dana 35 in my XJ...

Are you still running 30 spline shafts on your 44, and 31 spline on your 8.8?

What ratio should you put in with a LS 6.2 with a 6l80?

I'm wondering if anyone knows how to identify if your tj has an abs system. It's a 2006 model x. Did TJ's even have ABS?

How tall are those lift springs? Also looks like you have coil spacers in the front? How tall are they? Thanks

37s with 5.13 gears should suffice if you have the 4:1 T case, right?

Wouldn't the HP Dana 30 be the preferred one to use?

I have a 98 TJ gonna run high fenders. But bouncing back in forth between 4&6 inch lift. What would you recommend??

My thinking has been 1.9 TDI + 4.88 + 35'' tires.