Buying a JK Unlimited Rubicon 3.8 or 3.6 what to look out for

[flyreels]

Ok I have the bug, I was going to buy an older TJ pre 2005 but I have looked about and decided to buy a JK Unlimited Rubicon (i like the idea of a 4 door for what I want) now which one to get, do I buy the 3.8 or 3.6 is there any known problems to look out for on a second hand one?
Second is there any problems with the 6 speed manual or are the autos a better box. It wont get any hard off road use and I don't mind autos but if the manuals are a better box then I will get one, I just want one that will give me the least problems if looked after and don't know which option would be more reliable so any help would be appreciated.
Cheers Peter

[JKlamb]

Can only comment on the 3.6. This came out in 2012 and there has been a few engines with a head problem, I have a 2012 3.6 and nearly 40000km on it and no dramas. From all reports the 3.6 is a better engine and the pick of gearboxes is the auto box. With the release of the 3.6 they gave it a new auto gearbox. Not to sure of any problems in the manual behind the petrol engine but has suffered behind the diesel. Also the interior of the 2012 is better. Hope this helps

[Banshee]

Pretty much "as above" from a 3.8 owner. I have the manual. No major issues but from all reports the 3.6 is the better engine on power and fuel usage.

The manual box had issues with the torque from the CRD, so they downrated the engine when hooked up to a manual box. Also the dual mass flywheel was very expensive to replace when it wore out. No such issues on the petrol engine due to lower torque and regular flywheel.

[MDK]

Originally Posted by Banshee

Pretty much "as above" from a 3.8 owner. I have the manual. No major issues but from all reports the 3.6 is the better engine on power and fuel usage.

The manual box had issues with the torque from the CRD, so they downrated the engine when hooked up to a manual box. Also the dual mass flywheel was very expensive to replace when it wore out. No such issues on the petrol engine due to lower torque and regular flywheel.

Do the petrols have normal flywheel and only diesels dual mass?

[humdingerslammer]

JKU 3.8 Rubi... I have had mine new for 7 years now...engine a bit sluggish but a proven performer that u can't kill unless u r stupid with it. Leave it alone in my opinion. 165000k no dramas... need to work the revs for best performance when towing etc. Gearbox perfect (manual).. Rubi stronger than standard unlimited model...Clutch ok ... mine burnt out at 80000km (my fault) but if it hasn't been changed at all I would change it out out to a stronger duty one when it is buggered (Centerforce clutch in mine and much better performance from it. Change throw out bearing at the same time). Costs about $550 delivered from USA and about $2000 to fit (a day and a half of labour). Auto prob better if u r wanting it as a daily driver. Adequate as a tow vehicle (will do light weight trailer/van easily) but chews juice and need to keep revs up. U cld re-programme the ECU tune but the gains are not worth the effort and cost.

You will probably need to change all front suspension bushes, ball joints and drag link and tie rod ends to avoid problems with death wobbles. Buy all the gear from the USA (Quadratec or Morris 4x4) as better than half the price (delivered) here & the savings can be used to get it all fitted. Also change oxygen sensors (4 of them) because they will more than likely be burnt out and new ones will keep fuel use at maximum efficiency. Also change sway bar links to stronger "disconnect" ones as the standard ones r not that strong a break easily on full flex in my experience. I am replacing mine with JKS disconnects which r physically thicker and stronger... make sure when ordering gear it will fit RHD version because some parts from USA suppliers won't (they r LHD over there... most stock parts fit both models but not all. Make sure that the electric sway bar disconnect works as this can be expensive to change if buggered esp if worked in mud. Check wheel bearings for play as well.

Might want a 2" lift...and better springs. U won't need more. OE shocks r OK but a bit harsh... if Ok leave them on. I replaced mine for BIlstein and these r great. The standard Rubi JKU has enough height/clearance if u r not wanting to be too hard core. The springs will definitely sag (probably have) as the OE ones r not that good for load carrying. Put HD ones on the back for sure.

Upgrade the headlights by fitting 60-80-100+ halogen or Xenon (better) globes... better still change the lens assembly (Delta on mine) for even better light. The OE lights r truly crap. Don't put stronger wattage globes in the head light assembly as it will melt or worse cause a fire.

U cld buy a front and rear bull bar but why? Might already have one fitted. They add weight and not much else... protection perhaps if u r a bush basher...

Fit better rubber... decent all terrain best and make sure wheel balance is perfect and wheel alignment also (toe in no more than 3 degrees, I think).

The JKU is the best option for space. handling, stability I reckon. I have been everywhere in mine (not quite I guess) and like a pig in mud.... it still turns heads with how it looks, where it has been and with what it can do. People were amazed when they saw it on the Canning Stock Route.... no dramas at all, didn't get stuck or hitched up once... and it pulled out my bother's Landrover Discovery twice!!!

It's a sturdy beast stock, and very capable.


Hope this helps.

[JasperJ]

Originally Posted by Banshee

The manual box had issues with the torque from the CRD, so they downrated the engine when hooked up to a manual box.

That's not quite right, but probably irrelevant to this conversation.
The CRD Manual came out with 410 N.m. whereas the Auto had 400 N.m. Later the Torque remained at 410 N.m for the Manual but was uprated to 460 N.m for the auto.

Originally Posted by MDK

Do the petrols have normal flywheel and only diesels dual mass?

Correct only the CRD has the dual-mass flywheel. I'm still on the original clutch after 6 years. Dual mass clutches have to be treated differently from the single mass unit or you'll kill it quickly as some have found. I tow fairly regularly with mine including a loaded horse float.

Back to the OP's question. In the time I've been keeping an eye on the JK since I thought to myself I have to have one of these back in 2007, there have probably been about the same amount of issues raised on here with both engines. Personally given the choice I'd go for the newer one, generally less km's, better fuel economy and better resale as it is newer.

Cheers

[Banshee]

Fair enough, Jasper. I stand corrected.

Yes, single mass, I currently have ~125,000km on mine with no problems.