Another "Running 40's" thread

[Medsker]

I would like some opinions on my plans to run 40” tires. My Jeep Wrangler is a 2024 392 with the XR Package so it has the greater strengthened axles (Full Float Rear) with 4.56 gears. I don’t think I’ll have to re-gear with the V8. I was thinking of the following:

• Front Fender Chop
• Inner Fenders
• For now Cheap Rock Rails
• Teraflex Adjustable Spare Tire Mount
• APEX Through Shaft Steering Ram (I already have the boost kit)
• Teraflex 3.5 inch Lift
• Teraflex Front Lower Control Arms
• Falcon 3.3 Adjustable Shocks
• Teraflex 1.75 Wheel Spacers
• Front Chromoly Axles
• Front Axle Truss
• Tires will probably be Toyo R/T Pro 40x12.50R17E

I know wheel spacers have mixed reviews so I may try to sell my XR wheels and tires and buy new wheels with appropriate offset (Probably -38). I’d have to sell my wheels and tires (35” BFG KO2’s with 8-10/32nds left) for $1400 to help pay for the new wheels. The trim rings have been powder coated Sarge Green and they probably have a couple of scratches on them. They also have the APEX RPV Valves on them.

This is all depending on the wife of course but she hasn’t said no yet which is a good sign.

So what do y’all think?
Wheel spacers okay or no?
Will I get $1400 out of my XR Wheels and KO2 tires?

Thanks in advance!

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[Cagle]

Do it. I ran 40s with spacers, and everything was great ,without the V8. The new full floating rear end with the unit bearings on the outside is way better than the old setup. So you should be fine.

 

[Medsker]

Do it. I ran 40s with spacers, and everything was great ,without the V8. The new full floating rear end with the unit bearings on the outside is way better than the old setup. So you should be fine.

Thanks for the encouragement and info!

I am waiting to hear back from my shop to see what it will all cost and if I can afford it all.

 

[Gorilla57]

Are you actually gonna wheel the JL with 40s or just "mall crawling" it? Legit question because of the t-case that's in the 392 and the ability to kill it wheeling.

 

[Medsker]

Are you actually gonna wheel the JL with 40s or just "mall crawling" it? Legit question because of the t-case that's in the 392 and the ability to kill it wheeling.

I haven't been to a mall in years I love to wheel it but when I wheel, 90% of it is dirt roads, 5% easy rock crawling, and 5% medium rock crawling. I try to go out once a week but that doesn't always work. Life gets busy sometimes....

I've researched this and the t-case seems to go bad when people don't move it into four wheel high when they are on the dirt and leave it in four auto. If you don't put in four high the clutches engage every time you go over an inconsistent bump. I always run mine in four high off-road so I'm hoping it will last a while.

 

[Gorilla57]

I haven't been to a mall in years I love to wheel it but when I wheel, 90% of it is dirt roads, 5% easy rock crawling, and 5% medium rock crawling. I try to go out once a week but that doesn't always work. Life gets busy sometimes....

I've researched this and the t-case seems to go bad when people don't move it into four wheel high when they are on the dirt and leave it in four auto. If you don't put in four high the clutches engage every time you go over an inconsistent bump. I always run mine in four high off-road so I'm hoping it will last a while.

If that's all the wheeling you are doing, what's the reason for going 40s? I do plenty of pretty extreme stuff in my JL with 37s. Trust me when I say I understand life getting in the way.......

The t-case will still slip if you put it into 4H or 4L. The clutches are not truly locked, just high pressure placed on the clutches. Watch WFO vids on them going out to rescue 392s with trashed t-cases. The 392 power, combined with 40's, will cause way too much binding up and something has to give.

But, if you really "have" to have 40s, your list seems pretty inclusive....

 

[Medsker]

I'll be the first to admit the 40's are more for looks then anything else. I had 39's on the Jeep that burned down and I loved the way it looked. I did a few more hardcore trails with my old Jeep. I'm sure I could do everything I want on the stock 35's but boy do I love the look of the big tires. Of course aired down they also smooth out the ride more with the taller sidewall.

I hadn't heard that about the t-cases. I'll have to look into that more. And maybe start saving up for an Atlas next. I have the extended warranty so it would be covered but still a royal pain if it leaves me stranded somewhere.

Glad to hear you think my list is good also! Thanks for your feedback.

 

[3TV]

I wouldn't say the t-case is all that fragile in a 392. I've been wheeling mine for three years. Two years were on 37s and one year on 40s. That includes three trips through the Rubicon, every trail in Moab at least twice, and countless other trails. No problems with the t-case yet, but it is on my list, right after 1-tons, which I keep putting off as well.

With the description of the type of four wheeling you plan to do and knowing not to use it in 4-Auto, I wouldn't worry too much about it.

 

[tjeeper]

I tried 40s with the stock 4.56 gears. I didn't like it. It was like starting in 2nd. I got 5.13 gears installed.

I tried to fit Artec front inner fenders. Artec gave me a vague answer when I asked if they would fit. They didn't. I ended up getting a Motobilt windshield fluid reservoir and NextVenture inners. This is with wheels with 3.5" of backspacing.

I decided I needed PSC hydro assist because I couldn't turn on the pavement without moving the Jeep.

My advice is to stick to 37s and save yourself the $10k in upgrades you are going to need to go to 40s. That doesn't even include having to replace the axles with 60s if you end up breaking the 44s (which is my plan if I break the stock axles).

 

[wibornz]

you will need to adjust your bump stops more so in the rear than the front And trim the seams in the back if you flex the Jeep much.
I have a 4 inch lift and run 40s around town. Mall crawling basically.. I go back to 37s for most off roading.

 

[nyglt56]

I personally wouldn't run 40s with the full time 4WD, D44s and the 392 combo. That's a lot of torque.

 

[failsafe306]

I would upgrade the rear shafts to chromo as well.

 

[Medsker]

I would upgrade the rear shafts to chromo as well.

With the full-float I'm not as worried because you can pull out the broken shaft and still keep driving. but that's a good idea. The only ones I can find on the market is RCV's and they are quite $$$ so I'm hoping that more will hit the market that are more reasonably priced.

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