Topic: Switching to an LJ. Opinions?

[stan98tj]

Got word back today that my cyl head is toast. Basically the same thing that happened to the originally motor at 85k has happened to the rebuilt one at 46k. The head will be replaced but I no longer wish to spend anymore $$ towards this engine or another 4cyl. I really think that with my deeper gears and 3spd and sustained highway driving at 60 mph (3200 rpm ) is just too much for this little motor. If it were a trail only rig or driven just around town, it would do well, but as soon as you get up over 55, it's screaming. And I want something i can drive to bag from the trails.

So I've decided I want an LJ. My plan is to buy one swap my axles and suspension out and into the LJ and sell my TJ with the LJ lpdana30 and d44 along with my 33s, motor mount lift, 1" body, SYE and my rock rails. My tummy tuck skid will be sold to a friend as it won't fit the LJ.

I thought about parting out, but it will take a while and I thought about just building the LJ axles, but I think my hp30 and 8.8 are stronger than what came stock on an LJ...and I've already spent the money.

The LJ will be automatic, running 4.56 gears, and an atlas 4speed. I figure I'll run 35s. My current suspension was set up for 35s so I should be able to run them on the LJ.

Im still in the market for the diesel swap once hpa offers the auto conversion. In the meantime I'll have the LJ 4.0
What do you guys think of a 6cyl auto with 35s and 4.56 ?
Also , what is considered "high mileage" for the 4.0? +125k? +100k?

[Jeffy]

Im still in the market for the diesel swap once hpa offers the auto conversion. In the meantime I'll have the LJ 4.0
What do you guys think of a 6cyl auto with 35s and 4.56 ?
Also , what is considered "high mileage" for the 4.0? +125k? +100k?

With a 4.0L, I doubt you'll want nor need a diesel.  The setup should be fine.

As for high mileage, it really depends.  Do they have a binder for of receipts for the vehicle?  Do they have a maintenance or gas log?  If it's well maintained 120 or even 140 shouldn't be a problem.  Though I'd shoot for below 100K.  With more mileage, little things are probably going to be more of a problem.  Sensors, ans such...

[stan98tj]

With a 4.0L, I doubt you'll want nor need a diesel.  The setup should be fine.

As for high mileage, it really depends.  Do they have a binder for of receipts for the vehicle?  Do they have a maintenance or gas log?  If it's well maintained 120 or even 140 shouldn't be a problem.  Though I'd shoot for below 100K.  With more mileage, little things are probably going to be more of a problem.  Sensors, ans such...

Can't shake me from that diesel swap :)
I'll be doing it soon as they set up a package. I've been talking to my 4.0 friends and for the most part they feel like their engines are bulletproof. Do you know of any inherent flaws with that engine? Parts that generally fail in the model year I'm looking at? I've never had a 4.0 so I'm just wondering if there's anything in particular I should look for

[Jeffy]

The 4.0L is basically a 2.5L with two more cylinders.  The only problem I've ever heard is the coil packs of the later models failing occasionally.

[stan98tj]

The 4.0L is basically a 2.5L with two more cylinders. 

So what you're saying is I can expect catastrophic failure at 86k except Ill grenade 6 pistons rather than 4

[Hunter02]

Basically the same thing that happened to the originally motor at 85k has happened to the rebuilt one at 46k. I really think that with my deeper gears and 3spd and sustained highway driving at 60 mph (3200 rpm ) is just too much for this little motor. If it were a trail only rig or driven just around town, it would do well, but as soon as you get up over 55, it's screaming.

What in the world were you doing?   Gears?
I know TJs that have 250k+ and YJs with over 320k and have never had a problem.
My '98 TJ has 3.73s and 31X10.50s and I don't think it has ever seen 3000rpm.
55mph puts the tach at about 2200.
My sister bought the last model year TJ/LJ and she loves it. She uses it as a daily driver and runs it from the Jersey Shore up to the middle part of Maine twice a year.
As for 4.0L weaknesses, besides the coils that someone mentioned, the exhaust manifold likes to break between the 1st and 2nd cylinders or the 5th and 6th.
If you're looking for 'balls', you can get a rotating assembly off of Ebay for about $800 that will turn your motor into a 4.6 stroker with about 300hp and matching torque. That's what I'm in the middle of building right now for a Jeep RatRod I'm putting together. I was going to go Chevy I-6 with a power glide, (you know, ol skool) but I thought a slightly built 4.0 would be just as kewl.
Hunter

[stan98tj]

What in the world were you doing?   Gears?
I know TJs that have 250k+ and YJs with over 320k and have never had a problem.
My '98 TJ has 3.73s and 31X10.50s and I don't think it has ever seen 3000rpm.
55mph puts the tach at about 2200.
My sister bought the last model year TJ/LJ and she loves it. She uses it as a daily driver and runs it from the Jersey Shore up to the middle part of Maine twice a year.
As for 4.0L weaknesses, besides the coils that someone mentioned, the exhaust manifold likes to break between the 1st and 2nd cylinders or the 5th and 6th.
If you're looking for 'balls', you can get a rotating assembly off of Ebay for about $800 that will turn your motor into a 4.6 stroker with about 300hp and matching torque. That's what I'm in the middle of building right now for a Jeep RatRod I'm putting together. I was going to go Chevy I-6 with a power glide, (you know, ol skool) but I thought a slightly built 4.0 would be just as kewl.
Hunter

You have stock gears. I have deeper gears. At 55mph I'm over 3k.
The 4 banger works well as an around town vehicle or works well as a trail rig but not both.

[chrisfranklin]

I like the LJs -- probably what I'd buy in the 97-06 run

[dwtaylorpdx]

Hmm.. I have 220K on my 94 YJ,, I rebuilt the engine and warmed it up with a Hesco cam , Good pistons some mild head work heavy duty valve springs and a full B&B at 175K..

My driving style is 5 forward speeds pedal to the floor, 3500 cruise at 75+ and I shift at 6K... a lot.. 
Its my toy and it does not get treated nicely.. In the sand its been run at 6500 for a full flight out of a bowl many times..
Note: I would not try that with a stock motor.. But I didn't treat it very well for the first 175 either..
I occasionally go run sweep for WRC/Rally America and thats a tough weekend on the thing..

Did you use Hypeutectic coated pistons on the rebuild? Because that is what they had stock from about 93 onward..
The rod angle and the piston design cause a fair amount of slap and they wear a lot if the skirts are not coated.

I literally have driven 3500 miles in a week on the freeway at 75, pulling the Rockys desert etc.. I have 4.56 and 32" tires..

I want a diesel as well .. I want some mileage,, Heck a chevy v8 gets better mileage than the 4cyl ever did..

I run good synthetic oil, change it about ever 5 to 6K and regular unleaded fuel if its below 80 degrees out premium if its over 80.

I also ran Joe Gibbs breakin oil the first 5000 miles changing it out at 2500.
There are well documented issues with newly rebuillt engines and the new green low sulfur/zinc oils.

The Mopar injection is pretty much crap, it pays to keep the injectors clean, and swap the O2 regularly on them (I do mine about every 50K. ) Also the TPS should be checked regularly as if it gets any worn spots it will throw the fuel curve out the window. Also the ECU water temperature sensor it should be checked as well, I find they are good for 75K ish, some go forever some are shot at 20K.. YMMV! The ECU and the gauge are using separate senders (Another Mopar stupidity.. ) the ECU will not fault the sensor unless it goes totally open which almost never happens... SO you need ot check the resistance stone cold and at full temp once in a while.

The 6 does not have any mechanical advantages on the 4 other than a better timing chain.. (No adjuster) And a slightly smoother operating state because the 6 is more naturally balanced than the 4 banger...

[stan98tj]

Hmm.. I have 220K on my 94 YJ,, I rebuilt the engine and warmed it up with a Hesco cam , Good pistons some mild head work heavy duty valve springs and a full B&B at 175K..

My driving style is 5 forward speeds pedal to the floor, 3500 cruise at 75+ and I shift at 6K... a lot.. 
Its my toy and it does not get treated nicely.. In the sand its been run at 6500 for a full flight out of a bowl many times..
Note: I would not try that with a stock motor.. But I didn't treat it very well for the first 175 either..
I occasionally go run sweep for WRC/Rally America and thats a tough weekend on the thing..

Did you use Hypeutectic coated pistons on the rebuild? Because that is what they had stock from about 93 onward..
The rod angle and the piston design cause a fair amount of slap and they wear a lot if the skirts are not coated.

I literally have driven 3500 miles in a week on the freeway at 75, pulling the Rockys desert etc.. I have 4.56 and 32" tires..

I want a diesel as well .. I want some mileage,, Heck a chevy v8 gets better mileage than the 4cyl ever did..

I run good synthetic oil, change it about ever 5 to 6K and regular unleaded fuel if its below 80 degrees out premium if its over 80.

I also ran Joe Gibbs breakin oil the first 5000 miles changing it out at 2500.
There are well documented issues with newly rebuillt engines and the new green low sulfur/zinc oils.

The Mopar injection is pretty much crap, it pays to keep the injectors clean, and swap the O2 regularly on them (I do mine about every 50K. ) Also the TPS should be checked regularly as if it gets any worn spots it will throw the fuel curve out the window. Also the ECU water temperature sensor it should be checked as well, I find they are good for 75K ish, some go forever some are shot at 20K.. YMMV! The ECU and the gauge are using separate senders (Another Mopar stupidity.. ) the ECU will not fault the sensor unless it goes totally open which almost never happens... SO you need ot check the resistance stone cold and at full temp once in a while.

The 6 does not have any mechanical advantages on the 4 other than a better timing chain.. (No adjuster) And a slightly smoother operating state because the 6 is more naturally balanced than the 4 banger...

Maybe I just really have bad luck, or this particular jeep is cursed. But you have to wonder, first engine died at 86k, replacement engine died at 47k...
That's enough for me to want to stay away from another 4 banger...