Going 40s... New concerns...

[Pescatoral Pursuit]

I've traded my fear of getting stuck on the trail, to breaking down on the trail, lol.

Went from 37 KO2s and a 3.5 lift, to 40" Patagonia M/Ts and 5.5 lift. Factory gears, axles.

I feel better about not getting rutted out (been stuck twice; winched myself out both times) but now I'm concerned something might break.

JTRD and I'm not a "send it" guy: always carefully wade in trusting lockers and a good winch point ahead.
Not a rock crawler in Central Florida but sand, clay and mud trails with holes ruts divets here and there.

All of my wheeling is solo vehicle and usually no passengers.

Is Mr calculatedly careful justified in his concerns or overly paranoid?

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[Lunentucker]

You're gonna break something. I don't know when or what, but you are. ?

 

[High Alextude]

You’re going to need a ladder to get in that monster truck! Part of me says go big or go home, then there is the rational part that says, if you couldn’t do it in 37’s, will 40’s be a big difference? I don’t know, but I’m excited to see what you do!

Are you sure factory gears can handle that? What does the 5.5 lift come with? Maybe it would be better to invest in more recovery gear instead?

The worst thing you can do is ask the internet how you should spend your money and if you’re paranoid, haha.

Here you go: Www.webmd.com

 

[rharr]

Stock 3.73 gears seem way off for 40's on a eco D. You are going to make that trans work with that setup.

I would also truss the front axle for cheap insurance. 40's is a lot of weight for crappy castings to handle. Might also want to look at up graded ball joints. Seen a lot of newer jeeps on Trail maters channel needing replacement help on the trail cause the OEM blew up. Seems to be a common failure point and most were only running 37' and 38's.

 

[Chief_jeep]

Something will break eventually. I guess the question is would you rather spend money now or later. Running 40s is a ton of extra rotating mass compared to a 37, especially a k02.
Here are a few things you could upgrade to support the 40s.

For starters your pinion angle is probably awful with a 5.5” lift. Upgrade to a 1350 drive shaft drive shafts or carry spare u joints

axle shafts

Knuckles

Ball joints

truss the axle

or sell your perfectly good Dana 44 and buy one ton axles

 

[Sandevino]

The weak link is now the axle shafts.

440 ft. lb. torque + sticky tires = busted shafts

You don't send it so you should be relatively fine. If it looks sketchy... bypass it.

The other x-factor now is the pump delivering more fuel to the engine with the larger wheels and stock gearing. Look into gears to bring the RPM's back down and chromoly shafts if you want to bulletproof the axles.

 

[Renegade]

RCVs in the front and chromoly shafts in the rear. Take it easy, and have fun!

 

[RhinoJT]

The oldest discussion in jeep off-roading. IMHO, if you are going to run 40s on stock/ near stock drivetrain, you have to be aware that there will be some limitations. Simple mechanics. Bigger tire equals longer moment arm from the center, add in huge amounts of low end torque with the diesel and get hung up in the rocks, at some point your going to have to put your pride aside and pull out the winch. As well, ball joints, u joints and the like will wear quicker from the extra weight and moment arms from wider bigger tires. For me, taking the kids out into the woods to go play on rocks, i didn’t want to play the odds and deal with screaming tantrums stuck in the desert/mountains which a broken vehicle. I went straight to kingpin 60s. With that said, shit can still break, just less variables in the equation for me. Also, if your break, now we all get to pull you out. ( half the fun though, and love this community because it’s leave no man behind style. We are getting you out)
To put it straight, it can be done, just can’t be a cowboy. For me, I wanted to drop 40s and the hammer and have a good feeling she was going to most likely make it out alive! Plus, I would be lying if I said i didn’t do it for the looks, (badass with big rubber)!!

 

[Sandevino]

The sound of your wife, girlfriend or significant other bitching and whining while stranded will haunt your dreams...lol

 

[Pescatoral Pursuit]

You are going to make that trans work with that setup.

Not too much in 4L with a 4:1 TC driving in mostly a straight line.

Running 40s is a ton of extra rotating mass compared to a 37, especially a k02.

Pats are a lighter 40 coming in shy of 90lbs.

For starters your pinion angle is probably awful with a 5.5” lift.

Not terribly so. I'll get a pic tomorrow. I did install a RC Cardan front driveshaft and the rear has a carrier bearing spacer.
I also bought but have yet to install teraflex rear upper control arm relocation brackets just to help the pinion angle at flex.

Look into gears to bring the RPM's back down and chromoly shafts if you want to bulletproof the axles.

They are on the short list.

RCVs in the front and chromoly shafts in the rear. Take it easy, and have fun!

That and a little truss work and we should be golden, right?

Bigger tire equals longer moment arm from the center, add in huge amounts of low end torque with the diesel and get hung up in the rocks,

This is Florida, brother. No rocks to speak of. I wouldn't begin to think I could get away with it if I was rock crawling.
40" Pats are about 15lb more apiece than 37" KO2s. Yes there's also more leverage to consider.

Plus, I would be lying if I said i didn’t do it for the looks, (badass with big rubber)!!

Oh yeah. Been eatin me up having to look up to those guys at the intersection! ?

The sound of your wife, girlfriend or significant other bitching and whining while stranded will haunt your dreams...lol

My wife of 30 years watches me safely from the comfort of Life360, lol.
I carry a full suite of recovery gear. That and prudence has kept me self-sufficient thus far.

You’re going to need a ladder to get in that monster truck! Part of me says go big or go home, then there is the rational part that says, if you couldn’t do it in 37’s, will 40’s be a big difference? I don’t know, but I’m excited to see what you do!

6'3" and all legs. Getting in the truck is the easy part! Has been entertaining watching my 5'7" missus climbing in and out like it's a treehouse, lol.
I think 6" and 40s is the natural evolution from 3.5" and 37s. My Jeep was a heck of a trail runner (except for the deeper rutted holes) in that configuration with Falcon shocks.

I don’t know, but I’m excited to see what you do!

Thanks! Me too! Stay tuned!

 

[Chief_jeep]

Not too much in 4L with a 4:1 TC driving in mostly a straight line.


Pats are a lighter 40 coming in shy of 90lbs.


Not terribly so. I'll get a pic tomorrow. I did install a RC Cardan front driveshaft and the rear has a carrier bearing spacer.
I also bought but have yet to install teraflex rear upper control arm relocation brackets just to help the pinion angle at flex.


They are on the short list.


That and a little truss work and we should be golden, right?


This is Florida, brother. No rocks to speak of. I wouldn't begin to think I could get away with it if I was rock crawling.
40" Pats are about 15lb more apiece than 37" KO2s. Yes there's also more leverage to consider.


Oh yeah. Been eatin me up having to look up to those guys at the intersection! ?


My wife of 30 years watches me safely from the comfort of Life360, lol.
I carry a full suite of recovery gear. That and prudence has kept me self-sufficient thus far.



6'3" and all legs. Getting in the truck is the easy part! Has been entertaining watching my 5'7" missus climbing in and out like it's a treehouse, lol.
I think 6" and 40s is the natural evolution from 3.5" and 37s. My Jeep was a heck of a trail runner (except for the deeper rutted holes) in that configuration with Falcon shocks.

Thanks! Me too! Stay tuned!

A 37" k02 weights 65 or 69lbs depending which you have. That's not only a 20lb difference, but it's a larger tire. Even if the tire was the same weight, a 40 is larger and have a lot more stress on all the components.

I wouldn't worry about your pinion angle for daily driving. It's when the suspension starts to droop. The carrier barring will help but 40's on a stock driveshaft is a weak point. Especially with the torque of the diesel.

But yes, your best bet is chromoly shafts, a truss and I'd do new ball joints. 13.5 inch tire plus offset wheels adds a ton of stress on those ball joints. They likely won't fail on the trail but it's an inevitable weak point that will need to be replaced.

Also braking which everyone forgets.... a 40 is heavy and if you're on a beadlock its even heavier. All that rotating mass is hard on the stock brakes. It's another benefit of going to a one ton axle. Its a full package that are made to handle the stress.

There are many people running 40s on stock and built 44's so it's definitely possible. In my opinion once you build a 44 you could've sold your 44 and upgraded to a 60 for a marginal cost. Especially if that axle breaks. The cost of a trail recovery, time without your vehicle and the new parts add up quickly.

Like @RhinoJT said, going to 40's gives you piece of mind of making it off the trail even though things can still break.
Personally, if I didn't want to take on the expense and project of one tons I'd stick to a 37 or a 38. If you liked your k02 the 39 ko2 would be a great tire to do shafts, u joint, ball joints and truss. It's really a large 38. It's a better tire in the sand than almost any MT and way better on the road. I had a 39 k02 and now on 40 Baja boss. The 39 k02 was better at everything besides really hard rocks and it's marginal. The only people that can tell the difference are Jeep people lol

 

[Jteakus]

Old school rule was anything bigger than a 35 needed tons. When 37's came out we all skirted the rule and got by running them by being easier on the throttle. The new gen 44's are stronger but the 40's will overwhelm them. Tons are expensive but if you do a cost comparison of all the upgrades needed to strengthen the 44's including a gear change and include the sale of your stock axles you will put a dent in the cost of tons.
When you get the 40's mounted up and are staring at them gaze under the Jeep and look at the diff. If that doesn't convince you to go tons hold a 4.56 D44 pinion gear in your hand and do the same. Best of luck whichever path you choose.

 

[MCATDT]

Sounds like you are set to go with 40's and got some good advice. I know you said you typically wheel alone but have you looked into joining a local Jeep club. I live in Central Florida as well and spending time with experienced wheelers has really helped me be better at picking lines and not getting hung up on the trail. My first couple of outings I got hung up and high centered and heard all the Gladiator jokes from the Wrangler drivers and as I took their advice and watched how others were navigating obstacles that really became a thing of the past and I am on 35's and a 3" lift. Now I am the one joking with the Wrangler drivers when they can't get through an obstacle and I was able to get through it easily. I think a combination of what you want to do and gaining some off road insights from others will probably decrease your chances of breaking something and add to your peace of mind as you move towards 40's. Bottom line is use the Jeep the way you want. I think you understand the risks associated with your plan so make the vehicle your own and have fun.

 

[Florida Mojave]

Well...... if you go with the tons - at least you'll be all set up for the Hemi swap!!! LOL!

 

[Pescatoral Pursuit]

I know you said you typically wheel alone but have you looked into joining a local Jeep club. I live in Central Florida as well and spending time with experienced wheelers has really helped

That's great. I've joined a few groups online and the over emphasis of "Never Go Alone!" is very off-putting, and the idea instead of "Be Prepared" doesn't quite get the same reception.
One of the reasons I bought a Jeep and modified it is to get away back into the woods, and I've been a little surprised at the lack of a spirit of independence which is what I thought the Jeep ethos was.

I think a combination of what you want to do and gaining some off road insights from others will probably decrease your chances of breaking something

While there's always something to learn, I'm new to Jeeps, not new to off-roading and modifying vehicles. I've been running Florida trails on and off for over 40 years and have a fair amount of experience with the obstacles presented, and the strengths and limitations of my conveyance. Creating this post is a great way to draw on others' experiences and tune a plan moving forward.

Bottom line is use the Jeep the way you want. I think you understand the risks associated with your plan so make the vehicle your own and have fun.

That's what I'm doing!

going to 40's gives you piece of mind of making it off the trail even though things can still break.
Personally, if I didn't want to take on the expense and project of one tons I'd stick to a 37 or a 38. If you liked your k02 the 39 ko2 would be a great tire to do shafts, u joint, ball joints and truss. It's really a large 38. It's a better tire in the sand than almost any MT and way better on the road. I had a 39 k02 and now on 40 Baja boss.

I knew up front without the investment into tons, that I'd be trading water fording and trail rut clearance for optimal performance, by effectively "self-governing" my right foot.
While the KO2s do great in the sugariest of sand, and even mud without airing down, their weakness is clay and the inability to clear tread.
What is your experience with their KM3s?

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