2001 XJ 2nd Wind Build

Greeting XJ enthusiasts. I recently considered trading in my XJ for a new F150 before it hit 100K miles. It needed new suspension, new tires, oil change, the whole 9 yards of maintenance. It seemed to be the right move fiscally, but I have decided that, emotionally, I would rather keep the XJ and give it new life for it's 2nd wind.

I came to this realization after having to tow a 1000 lb trailer up a completely mud soaked grade in stock trim with no problems. That was the first time it has ever seen mud and I did everything I could to wash it all out.

Make/Model: 2001 XJ Limited 4.0 Auto 4x4 Cloth
Miles: 100,150 Highway / 50 miles of mud (just recently)
Purchased: July 2007 w/ 40k miles
Add-ons: Rock sliders
New: Radiator
Needs: Shocks, springs, tires, ???
Concerns: Transmission shift a bit differently now
Future usage: 80% highway, 10% 1,500lb tow, 10% backwoods camping
Budget: Well, I was about to buy a brand new f150, but I don't want to spend more than necessary to satisfy my future usage.

So my question to the experts is, what do I do from here to make this truck last another 10 years / 100k miles for the usage I want out of it? Which products offer the best performance per dollar? If stock springs are more costly than a lift, let's do a lift. What about the tranny? Can I expect this thing to last or should I expect to replace it soon? What can I do to help with towing? If it does make sense to get a lift, what would be the best combo with tires/wheels? I'd like to keep the stock wheels, but if makes sense to replace them, that's fine too.

And, for the folks in VA, who are the best XJ mechanics to work on this? I'm not interested in performing the work myself because I always do a better job the second time around, and this is my first time around.

Many thanks!

The AW4 transmission is one of the most reliable transmissions ever built. They seem to outlast many engines. If the shift is off, you can try pushing the gray button on the manifold side of the TV cable. You can also drain the pan and refill with 3.8 quarts of Dex III ATF.

Your Jeep does not look like it has any major sag to it so the springs are probably OK. The suspension bushings may be tired and due for replacement. The motor and/or transmission mounts may be due for replacement. They either brake or sag.

Starting around 2000 the Jeep 4.0 came with a 0331 head casting which is notorious for cracking and putting coolant into the oil. Some people report that they crack for no apparent reason while others have problems after an overheat. On mine about 2 years after the thermostat failed shut I found coolant leaking into the oil. If the head comes off for any reason, replace it with a better casting.

The crank sensors can fail and cause no hot start or stall at traffic lights (they fail when the engine is hot). The throttle position sensor (TPS) can fail hot also, and cause stumbling or weird transmission shifting. Its right on top of the manifold and very easy to change. Only 2 T-20 (or T-25) bolts.

I would use the factory recommended 75w-140 synthetic gear oil in the axles particularly if you are towing.

Just keep the fluids clean and keep driving it.

My 01 XJ has 332,000 and is still going... still has the factory exhaust but I'll need to change the muffler.

md21722 said:

The AW4 transmission is one of the most reliable transmissions ever built. They seem to outlast many engines. If the shift is off, you can try pushing the gray button on the manifold side of the TV cable.

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Thanks, I will try this.

md21722 said:

You can also drain the pan and refill with 3.8 quarts of Dex III ATF.

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Alrighty, I'll do this too.

md21722 said:

Your Jeep does not look like it has any major sag to it so the springs are probably OK. The suspension bushings may be tired and due for replacement. The motor and/or transmission mounts may be due for replacement. They either brake or sag.

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Thanks. You can't see it under any tongue weight right now, but with about 250lbs back there, it sags enough to be noticeably off-level and also changes the steering characteristics when driving. Any recommendations with these facts?

md21722 said:

Starting around 2000 the Jeep 4.0 came with a 0331 head casting which is notorious for cracking and putting coolant into the oil. Some people report that they crack for no apparent reason while others have problems after an overheat. On mine about 2 years after the thermostat failed shut I found coolant leaking into the oil. If the head comes off for any reason, replace it with a better casting.

Click to expand...

As a matter of fact, I had bought a 2000 XJ 4.0 brand new and had this issue, but I had traded it in right after it started overheating and before I identified the issue. I saw a girl driving it about 4 years later (like a bat out of hell), so I guess she had it fixed.

md21722 said:

The crank sensors can fail and cause no hot start or stall at traffic lights (they fail when the engine is hot).

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I have hot start stalling and thought it was the injector closest to the exhaust manifold. I put some insulation between but didn't help much. How do I get this fixed for good?

md21722 said:

The throttle position sensor (TPS) can fail hot also, and cause stumbling or weird transmission shifting. Its right on top of the manifold and very easy to change. Only 2 T-20 (or T-25) bolts.

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Maybe this is what it is? I'll replace it anyway.

md21722 said:

I would use the factory recommended 75w-140 synthetic gear oil in the axles particularly if you are towing.

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Ok, is this an easy DIY?

md21722 said:

Just keep the fluids clean and keep driving it.

My 01 XJ has 332,000 and is still going... still has the factory exhaust but I'll need to change the muffler.

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Thanks, Oil changes are relatively cheap now, so I pay someone to do this, but should I get the blend or full syn?

Nick.

4.0 likes standard oil just fine. I think PO rebuilt mine at 140k but still going very strong at 210k.

Yes gear oil is very easy to DIY.

You can add shackles help lift rear a bit if you still have good arch

Synthetic is a waste of money. It's a tractor engine, it likes regular oil.

denverd1 said:

You can add shackles help lift rear a bit if you still have good arch

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Thanks, they're flat and I want a better road ride, wondering if a full OME system would help me tow in comfort?

Changing diff fluid is cake as long as you can use a ratchet and torque wrench. Just take out the bottom bolts on the cover, loosen the top ones and gently tap the cover with a rubber mallet, this will break the seal and most of the fluid will flow out. Then fully take the cover off, clean out the inside of all old oil(I use brake cleaner to do this), then wipe it out with rags. Then put Blue rtv around the gasket and bolt it back up, then take the full plug out and fill it until it reaches the bottom of the fill plug hole. All done