Should I get a TJ with 4.0 or JK with 3.8?

SHINTON

SHINTON

Well-Known Member
Joined
Mar 17, 2005
Location
Triad area of NC
So thinking semi-seriously of getting a "wheeling" Jeep and the wife is supportive because I am more likely to leave HER Jeep alone! (Her is new 2022 JLU Rubicon 4xe we got a few weeks back)

This would be something harderish core for me to get back into wheeling with, I would want to be able to drive it to work as desired, 25 minutes each way but have another SUV if (when) I break something and this rig would be down for a bit.

I am "thinking" 35-37s and a 2 door Wrangler, MUST be automatic... and I was looking at prices and mid to lower teens ($10-17ks) I am seeing TJ Rubicon and JK Rubicon which I think is what I really want to build. Axles are "done", lockers front and rear and the amount of lift vs fender cutting to fit the desired tires is my goal with minimal lift.

IOW.. if I can trim fenders or put on "super high clearance" fenders that will fit 35s with no lift I like that plan (or 37s with mild 2" lift / no drive shafts, etc)

So.. with all of that in mind, I am seeing Rubicon in my my price range, I kinda sorta think I want a 2 door JK Rubicon just because I have never owned a JK and honestly my ONLY hangup is the 3.8L that they used from 2007-2011. If YOU were buying and looking at TJ with 4.0 vs JK with 3.8 are there other features that would drive you one way vs the other? JK fits bigger tires stock with less lift... TJ/4.0 will run forever...?

I have owned 3-4 TJs with 2.5L and 4.0 (and XJs etc) so that is a well known engine with well known problems and solutions. But it is not "different" and JK would scratch my itch for a Jeep I have never owned.

I appreciate all input.. AND side thoughts on, "buy a sport and put lockers/chromolys) also welcome if I am spendign too much for Rubicon vs buying/building something. My longer term goal is to build something I may drag out and do Rubicon someday, Moab, "big bucket list" trails rig that I can pull behind my diesel pusher motorhome. Prob on trailer but flat tow also a really good possibility since we flat tow the JLU.

Pic of the RV and the 4xe below

Sam

storm e and dolly.JPG
 
If you want a JK, get a JK.

TJ, even if Rubicon, will cost you a lot more to put 35s+ underneath
 
The JK front housing needs knuckle gussets and sleeves or a truss to live with 35-37" tires, but the axles are better by any other measure.
 
Bebop said:
TJ, even if Rubicon, will cost you a lot more to put 35s+ underneath
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This

JK is overall a better starting point. So much more aftermarket available. While the 3.8 is a huge disappointment, you've got options. Or..just live with it's underwhelming delivery.

@Jason W. Having modded both extensively can give you better first hand experience owning/modding them
 
I had to figure the JK was a big step forward, but I just have heard over the years to avoid the 3.8. But then folks point out the 4.0 actually has less HP/torque so it is still an upgrade. I am leaning 75% JK so this helps and getting those 35-37s under there easier / cheaper, closer to OEM is a big draw for me. I am thinking I would rather have 35s on stock / OEM suspension vs 37s and lifted, especially considering I am thinking of flat towing, keeping stockish geometry.
 
Probably gonna piss some people off, but I don't care...

JK+LS+SD axles.

.....I can't believe I just suggested an LS swap. I feel kinda dirty....


But in all seriousness, I personally felt that the power to weight ratio is off on the jk, which ever v6 is in it. Sure it may have higher PEAK numbers, but I've always butt dyno'd the 4.0 as the better low end grunt motor. You can overcome that with gearing to an extent, and of course there are supercharger kits available. I do prefer the jk platform, even in 2 door form, they just seem more roomy, but I'm a big guy, and more stable on the road. I've driven TJ's, the extended TJ (LJ?), and JK's in stock form, and with various amounts of lift and tire sizes. I would go with a JK, unless I got a deal on a TJ I just couldn't say no to....like free.

My $.02, take it as you will.
 
I'd at least try to get a JK with a 3.6 to start with.
 
3.8 is ok, just watch for the oil consumption issues. Early 3.6 has rocker issues so even if you could stretch your budget for a 2012+ that would be a concern.

Having an LJ, I wouldn't consider a standard length TJ. And an LJ puts you in or above the price range of a 2 door JK.

As others have said it's going to cost more to reliably run 35-37s on a TJ/LJ.

All that being said, as much as I hate to say it... JK
 
I had a TJ on 33s and a JK on 33s at the same time a few years back. Both automatics. The 3.8L seemed to have more power than the TJ, didn't really seem sluggish at all. Probably should have kept the JK but it was one of the Jeeps we ran through the shop and was worth too much to hang on to.
 
Start with a JK, get the 3.6. The newer in your budget the better.

But if you’re set on a TJ, I got one…. Shameless plug lol.
 
SHINTON said:
I had to figure the JK was a big step forward, but I just have heard over the years to avoid the 3.8. But then folks point out the 4.0 actually has less HP/torque so it is still an upgrade. I am leaning 75% JK so this helps and getting those 35-37s under there easier / cheaper, closer to OEM is a big draw for me. I am thinking I would rather have 35s on stock / OEM suspension vs 37s and lifted, especially considering I am thinking of flat towing, keeping stockish geometry.
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Gear the piss out of it and don't weigh it down with needless "armor". It'll be gooder enougher.
 
I have a lot of experience with multiple platforms since I am always wanting to build / try something new. In relation to this post I have owned:

3 TJs (1 Rubicon in there)
1 LJ Rubicon

3 JKs with 3.8 (1 Rubicon in there)

2 JKs with 3.6 (both Rubicons)

1 JL Rubicon (2nd Rubicon 4Xe on order)

1 JT Rubicon

All were built to different levels. Aside from driver’s side exhaust manifold crack on all 3 3.8 JKs I never had issues. My 07 Rubicon was a heavy SOB on 37s and was geared 5.13s. No complaints with power.

as you stated it won’t be your DD I’d take advantage of the lower price of the 3.8 And build to suit.
 
I've got a 3.8 automatic JKU. If you get a manual, you could get away with the 4.10 gears in a Rubicon. I had to regear mine from 3.73 to 5.13. It's not the engine, it's the minivan gearing they stuck in the transmission. 3.73 gears were crap with 33s.

As for the lift, yeah dirt cheap to get 35s. For a JKU, You can get the Rancho 2" Sport Lift and improve on it (HD track bar, and other beefier items). For a JK, just get JKU Rubicon springs and some shocks (and the beefier track bar, steering, etc). Either trim the plastic fenders (free), or put a 1" body lift (factory look and covered wheels for some states).

I've put plenty of armor on mine. Still does 80 on the highway and plenty of power on the trail.
 
Own/have owned all 3. 4.0, 3.8 and 3.6. 4.0 and the 3.8 were autos. Both on 33s with stock gears. The 3.8 was better all around. 3.6 is a manual with stock gearing and a 6 speed manual. It's not winning any races and feels the most gutless of all unless you really rev the piss out of it. The 3.6 is also a very sensor heavy engine with its vvt. I've had to replace far more hard to get at sensors on it than anything else I've owned before. Bottom line, they all suck with factory gearing and I have no hate for the 3.8. It's a basic pushrod v6 and quite reliable.
 
Talking to @Rox&Mud the other day about their 3.6. Some parts are not available, nationwide backorder. Something to keep in mind if you find a deal on one with a check engine light.
 
As said if you gear the piss out of them, they arn't that bad. I would skip the rubicon premium, only gets you what 4.10 ish gears? not even close to what it needs on 35s. Somebody correct me if im wrong but the front d44 isn't a true 44 anyways?

Also if you want a small lift to clear 35s, find springs off of a 4dr hardtop/tow package jeep. The springs are numbered, the higher the better. Rubicon springs mean nothing in the jks. This gained right around 1.75 in of lift on my 2dr soft top jeep. and alignment was still in spec.
 
83oldyoda4x4 said:
I thought they had weaker axle tubes and C's compared to other 44's, but couldn't remember. Thus I said correct me if i'm wrong.
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Already noted that the tubes and the inner knuckles need to be reinforced. The u-joints are 1350 series, though. Bigger than standard 760x D44 stuff. Front is HP, rear is bigger R&P ("Super 44") than standard 44.
 
To me, all the later 4.0s are just dogs. Good grunt at idle to 2k but are breathless and gutless on the road. The earlier 4.0s, esp HO models, felt much much better.
 
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