This is a really, really common question we see a lot of. I'm going to try to answer it as best I can, and if anyone else has anything to add please free free to respond.
Rust
If you're in the market for a 1997-2006 Jeep Wrangler TJ the number one thing you want to look for over anything else is rust. The chassis of these vehicles is extremely prone to rust issues, especially if you're located in the mid-west, east coast or other areas where they use salt on the roads in the Winter time.
Rust can be a huge issue on these vehicles. I've seen rust so bad that it's literally caused the frames to snap in half while driving down the road. It's no joking matter as that can be life threatening and extremely dangerous should something like that happen.
Having said that, when looking to purchase a TJ it would be a wise investment to either have a professional shop to a PPI (Pre Purchase Inspection) or if you feel comfortable doing it yourself, make sure to crawl underneath the vehicle and inspect every nook and cranny for rust. A few areas of surface rust isn't a big deal as it can be treated easily. What you're looking for will be huge areas of rust, and it will usually involve the frame of the vehicle.
In addition to checking the underside, it's a good idea to hit the frame (possibly with a rubber mallet) to see if you can knock any chunks of rust flakes loose from inside the frame (another area prone to rust).
It's always a safe bet to purchase a Wrangler TJ that has been a west coast car (or somewhere warm) where they don't salt the roads. Those vehicles usually have a much better chance of being free of rust issues.
Engine
You might have heard from someone that Jeeps are unreliable. This is actually quite inaccurate as a properly maintained Wrangler TJ is probably one of the most reliable vehicles out there. Take into consideration that you're dealing with an iron block, iron head, underhead cam pushrod driven engine. That's basically a tractor engine, and if you know about tractors, you'll know they build those things to be bullet proof.
The 4.0 engine in the TJ doesn't have any notorious weak points other than the OPDA (Oil Pump Drive Assembly). If the OPDA is going bad you will know because it will make a loud sound that almost sounds like a laughing barrel of monkeys. If you hear this noise it's bad news, so either have it inspected before purchasing it or walk away. It's a cheap part to fix and very easy to do, but if it goes bad it can result it catastrophic engine failure.
Other than the OPDA, the 4.0 (like most other engines out there) is as reliable as they come. Change the oil, do the scheduled maintenance and you shouldn't have anything to worry about. It's not uncommon by any means to see these things running healthy with perfect compression well past 300k miles. I've seen some with half a million miles still on the original internals.
This engine may not be the best performing engine, and it may be a gas hog at that. However, it certainly was built with longevity and durability in mind. The 4.0 engine found in the Wrangler has been around since 1965 since AMC first introduced it. It's got a proven track record and it's stood the test of time.
Drivetrain
Make sure you look at the trackbar(s) for wear and slotting of the mounts, especially the front one. This can cause death wobble and a potentially very dangerous situation. Also make sure that the transfer case shifts into 4WD (both high and low range) and functions properly. If the rig came with or has been retrofitted with lockers, be sure test them as well.
It's also helpful to determine what kind of axles the vehicle has prior to purchasing it. The addition of Dana 44 axles makes the Wrangler worth a bit more money and more desirable over all.
Conclusion
Rust should be your first concern when purchasing any used Wrangler TJ. It is hands down the number one issue with all used Wrangler TJs, and you really do not want to purchase a vehicle with major rust issues as it will be a huge, huge money pit.
Other than rust, there's really nothing vehicle specific that comes to my mind that you should look for when purchasing a used Wrangler TJ. Just like any other vehicle, you want to make sure you know the maintenance history, get a good CarFax, make sure the vehicle has never had any major accidents, clean title, etc. Unless you're looking for a project stay away from the cheap Wranglers as they often always spell trouble.
The Wrangler TJ is notorious for having a high resale value. Expect to pay a good chunk of change for one that is well kept and in good condition. Do your homework first, and if you see one that you're unsure about (or just want a second opinion) post pictures and details up on the forum so we can help you decide. A lot of us on here have a huge knowledge of Wranglers and would be more than happy to give you our thoughts and opinions.
Last but not least, check out the sticky on stock Wrangler TJ specifications as it will give you a complete break down of all the factory trim packages, models, options and specifications.
Rust
If you're in the market for a 1997-2006 Jeep Wrangler TJ the number one thing you want to look for over anything else is rust. The chassis of these vehicles is extremely prone to rust issues, especially if you're located in the mid-west, east coast or other areas where they use salt on the roads in the Winter time.
Rust can be a huge issue on these vehicles. I've seen rust so bad that it's literally caused the frames to snap in half while driving down the road. It's no joking matter as that can be life threatening and extremely dangerous should something like that happen.
Having said that, when looking to purchase a TJ it would be a wise investment to either have a professional shop to a PPI (Pre Purchase Inspection) or if you feel comfortable doing it yourself, make sure to crawl underneath the vehicle and inspect every nook and cranny for rust. A few areas of surface rust isn't a big deal as it can be treated easily. What you're looking for will be huge areas of rust, and it will usually involve the frame of the vehicle.
In addition to checking the underside, it's a good idea to hit the frame (possibly with a rubber mallet) to see if you can knock any chunks of rust flakes loose from inside the frame (another area prone to rust).
It's always a safe bet to purchase a Wrangler TJ that has been a west coast car (or somewhere warm) where they don't salt the roads. Those vehicles usually have a much better chance of being free of rust issues.
Engine
You might have heard from someone that Jeeps are unreliable. This is actually quite inaccurate as a properly maintained Wrangler TJ is probably one of the most reliable vehicles out there. Take into consideration that you're dealing with an iron block, iron head, underhead cam pushrod driven engine. That's basically a tractor engine, and if you know about tractors, you'll know they build those things to be bullet proof.
The 4.0 engine in the TJ doesn't have any notorious weak points other than the OPDA (Oil Pump Drive Assembly). If the OPDA is going bad you will know because it will make a loud sound that almost sounds like a laughing barrel of monkeys. If you hear this noise it's bad news, so either have it inspected before purchasing it or walk away. It's a cheap part to fix and very easy to do, but if it goes bad it can result it catastrophic engine failure.
Other than the OPDA, the 4.0 (like most other engines out there) is as reliable as they come. Change the oil, do the scheduled maintenance and you shouldn't have anything to worry about. It's not uncommon by any means to see these things running healthy with perfect compression well past 300k miles. I've seen some with half a million miles still on the original internals.
This engine may not be the best performing engine, and it may be a gas hog at that. However, it certainly was built with longevity and durability in mind. The 4.0 engine found in the Wrangler has been around since 1965 since AMC first introduced it. It's got a proven track record and it's stood the test of time.
Drivetrain
Make sure you look at the trackbar(s) for wear and slotting of the mounts, especially the front one. This can cause death wobble and a potentially very dangerous situation. Also make sure that the transfer case shifts into 4WD (both high and low range) and functions properly. If the rig came with or has been retrofitted with lockers, be sure test them as well.
It's also helpful to determine what kind of axles the vehicle has prior to purchasing it. The addition of Dana 44 axles makes the Wrangler worth a bit more money and more desirable over all.
Conclusion
Rust should be your first concern when purchasing any used Wrangler TJ. It is hands down the number one issue with all used Wrangler TJs, and you really do not want to purchase a vehicle with major rust issues as it will be a huge, huge money pit.
Other than rust, there's really nothing vehicle specific that comes to my mind that you should look for when purchasing a used Wrangler TJ. Just like any other vehicle, you want to make sure you know the maintenance history, get a good CarFax, make sure the vehicle has never had any major accidents, clean title, etc. Unless you're looking for a project stay away from the cheap Wranglers as they often always spell trouble.
The Wrangler TJ is notorious for having a high resale value. Expect to pay a good chunk of change for one that is well kept and in good condition. Do your homework first, and if you see one that you're unsure about (or just want a second opinion) post pictures and details up on the forum so we can help you decide. A lot of us on here have a huge knowledge of Wranglers and would be more than happy to give you our thoughts and opinions.
Last but not least, check out the sticky on stock Wrangler TJ specifications as it will give you a complete break down of all the factory trim packages, models, options and specifications.
