Hello everyone,
Long time lurker who's appreciated the wealth of knowledge from this forum! Over the course of several years I took the knowledge gained from reading forums on repair and restoration work and I was able to overhaul quite a bit on my TJ throughout 2025.
Some backstory; My TJ was my first vehicle which I have now owned for almost ten years. During these years It has seen many different changes (that will possibly be covered in a full comprehensive build post) that over time became worn down as the Jeep accumulated miles. On top of the usual wear and tear, this particular TJ had not been treated kindly by it's previous owner and had a 4.0L that needed some serious attention that in my teen and college years I could not afford. After parking my TJ for half of 2024 stock piling parts and funds to get it back on the road, repairs were ready to be made. Without further ado, let's get into it:
The Engine Rebuild:
The elephant in the room was the aforementioned 4.0L, this engine had very apparent piston slap and the compression did not pass a leak down test. In an attempt to not chase multiple issues/risking having to tear apart the engine again, the decision was made to just completely remove the engine and rebuild it from the bottom up, only re-using the oil pan and valve cover. Below is the engine bay post-engine removal:
After the engine was removed, the engine was disassembled from the top down, the cylinder head was the first major component to come off which revealed what looks to be the early signs of the head gasket starting to fail. the valves appeared to have coolant on them and upon further inspection of the water jackets, surface rust was visible which also points to a failing head gasket as seen here:
*Note the faded discoloration on the valves.
Image of the entire deck on the 4.0L:
Close up on the rusting water jackets:
As the disassembly progressed, the poor condition of this engine became more and more realized. both exhaust manifolds (originals to this Jeep) were cracked, the timing chain had developed undesirable slack but not surprising given the amount of miles and age of this engine, and the cylinder walls were scored up from the piston slap over the years. all new manifolds, pulleys, a master rebuild rebuild kit, and a new block were ordered after the engine was completely taken apart.
*Note the hairline crack and extreme discoloration from age/heat cycles.
*Note the slack in the timing chain.
*Note the uneven wear and scoring on the cylinders leading to piston slap - a very well documented fault within TJs.
Not documented, but while waiting for parts to come in and in between days where the new 4.0L block was being machined, a few days were spent cleaning up the engine bay, with soap/degreaser, re-wiring the master wiring harness and accessories (KC's on the bumper and Hellas on the roof rack), and cleaning up the underside of the hood.
After about a month, the engine was complete and fully re-installed in the Jeep, the engine ran like clockwork and had not ran this well since the day I first got the keys for it. No more piston slap and the idling was smooth. In addition to the engine and pulleys being replaced, the following were also replaced with Mopar/proven OEM-like replacements:
The Suspension:
The next problem to address was the suspension. The shocks were an older design that were hydraulic and were beyond worn out and the bump stops had deteriorated. I elected to go with a set of budget and proven Rancho RS5000X shocks and OE bump stops and also took the time to clean up on the wheel wells and springs. Because the springs appeared to not have any sag yet are still in relatively decent shape, I will likely replace the springs later in 2026 along with the aging puck lift.
*Note the worn shock that had a bushing completely fall apart upon removal.
*Final result just before torquing the top of the shock to 17ft-lbs. The rear shocks and bump stops were also replaced but not photographed.
The Steering:
While underneath the Jeep, I had noticed several other things that needed attention, with the most important being the steering. All the ball joints had excessive play as did the drag link, tie rod, and steering stabilizer. With the cold weather approaching not many photographs were taken during the installation progress but I ended up going with the HD Rugged Ridge steering kit, Teraflex HD ball joints, and a new Teraflex 9500 stabilizer to replace my worn one. While the RR HD kit is a good kit for the purposes I use my TJ for (camping, mild rock crawling, city driving), a more cost-effective option likely would have been the ZJ upgrade. That being said, the RR HD kit is still a great product and I will continue to report on the longevity.
Miscellaneous Items:
At this point, the TJ was running and driving very well and there were just a few odds and ends that needed to be done. The first was a pinhole leak in the rear pinion seal. An OEM Dana/Spicer seal for a Dana 35 axle was ordered and installed utilizing a paint marker and lining up the exposed threads to set preload. The old seal came out relatively easily with a seal puller (appears previous owner put a general parts store seal in at some point). The surrounding area was cleaned up with a Scotch-Brite pad and the new seal was seated in followed by topping off the gear oil.
Next was a routine oil change, while the subject of the "best oil" for these engines is often debated, I opted to go with conventional 10w-30 VR1 oil and a Mobile 1 filter. As of the time of writing this post, the engine has responded nicely to this oil and filter and does not make excessive noise, burn, and no new leaks have appeared which has been reported with synthetic oils by other users. I also went ahead and changed the air filter while underneath the hood of the Jeep.
Lastly, while underneath I had noticed one of the transmission cooler lines running to the radiator had began to leak ATF on the pavement. A challenge arose with identifying which hose was the culprit as both were soaked in ATF+4. I elected to just replace both lines with 3/8'' SAE J1532 hoses and replace the worm clamps with a slightly better style hose clamp as I could not locally find constant tension hose clamps in that size. The end result solved the leak and cleaned up on the underside of the radiator quite a bit.
*Note both hoses being soaked in the photo above.
*Final result of the hose repairs.
That's it! 2025 was easily the biggest year for this Jeep given the extensive amount of work done over the course of one year. There is plenty more on this Jeep that I plan to address which includes but is not limited to:
Thank you for reading!
-S.
Long time lurker who's appreciated the wealth of knowledge from this forum! Over the course of several years I took the knowledge gained from reading forums on repair and restoration work and I was able to overhaul quite a bit on my TJ throughout 2025.
Some backstory; My TJ was my first vehicle which I have now owned for almost ten years. During these years It has seen many different changes (that will possibly be covered in a full comprehensive build post) that over time became worn down as the Jeep accumulated miles. On top of the usual wear and tear, this particular TJ had not been treated kindly by it's previous owner and had a 4.0L that needed some serious attention that in my teen and college years I could not afford. After parking my TJ for half of 2024 stock piling parts and funds to get it back on the road, repairs were ready to be made. Without further ado, let's get into it:
The Engine Rebuild:
The elephant in the room was the aforementioned 4.0L, this engine had very apparent piston slap and the compression did not pass a leak down test. In an attempt to not chase multiple issues/risking having to tear apart the engine again, the decision was made to just completely remove the engine and rebuild it from the bottom up, only re-using the oil pan and valve cover. Below is the engine bay post-engine removal:
After the engine was removed, the engine was disassembled from the top down, the cylinder head was the first major component to come off which revealed what looks to be the early signs of the head gasket starting to fail. the valves appeared to have coolant on them and upon further inspection of the water jackets, surface rust was visible which also points to a failing head gasket as seen here:
*Note the faded discoloration on the valves.
Image of the entire deck on the 4.0L:
Close up on the rusting water jackets:
As the disassembly progressed, the poor condition of this engine became more and more realized. both exhaust manifolds (originals to this Jeep) were cracked, the timing chain had developed undesirable slack but not surprising given the amount of miles and age of this engine, and the cylinder walls were scored up from the piston slap over the years. all new manifolds, pulleys, a master rebuild rebuild kit, and a new block were ordered after the engine was completely taken apart.
*Note the hairline crack and extreme discoloration from age/heat cycles.
*Note the slack in the timing chain.
*Note the uneven wear and scoring on the cylinders leading to piston slap - a very well documented fault within TJs.
Not documented, but while waiting for parts to come in and in between days where the new 4.0L block was being machined, a few days were spent cleaning up the engine bay, with soap/degreaser, re-wiring the master wiring harness and accessories (KC's on the bumper and Hellas on the roof rack), and cleaning up the underside of the hood.
After about a month, the engine was complete and fully re-installed in the Jeep, the engine ran like clockwork and had not ran this well since the day I first got the keys for it. No more piston slap and the idling was smooth. In addition to the engine and pulleys being replaced, the following were also replaced with Mopar/proven OEM-like replacements:
- Spark Plugs
- Oil Pressure Sensor
- IAC Valve
- Starter
The Suspension:
The next problem to address was the suspension. The shocks were an older design that were hydraulic and were beyond worn out and the bump stops had deteriorated. I elected to go with a set of budget and proven Rancho RS5000X shocks and OE bump stops and also took the time to clean up on the wheel wells and springs. Because the springs appeared to not have any sag yet are still in relatively decent shape, I will likely replace the springs later in 2026 along with the aging puck lift.
*Note the worn shock that had a bushing completely fall apart upon removal.
*Final result just before torquing the top of the shock to 17ft-lbs. The rear shocks and bump stops were also replaced but not photographed.
The Steering:
While underneath the Jeep, I had noticed several other things that needed attention, with the most important being the steering. All the ball joints had excessive play as did the drag link, tie rod, and steering stabilizer. With the cold weather approaching not many photographs were taken during the installation progress but I ended up going with the HD Rugged Ridge steering kit, Teraflex HD ball joints, and a new Teraflex 9500 stabilizer to replace my worn one. While the RR HD kit is a good kit for the purposes I use my TJ for (camping, mild rock crawling, city driving), a more cost-effective option likely would have been the ZJ upgrade. That being said, the RR HD kit is still a great product and I will continue to report on the longevity.
Miscellaneous Items:
At this point, the TJ was running and driving very well and there were just a few odds and ends that needed to be done. The first was a pinhole leak in the rear pinion seal. An OEM Dana/Spicer seal for a Dana 35 axle was ordered and installed utilizing a paint marker and lining up the exposed threads to set preload. The old seal came out relatively easily with a seal puller (appears previous owner put a general parts store seal in at some point). The surrounding area was cleaned up with a Scotch-Brite pad and the new seal was seated in followed by topping off the gear oil.
Next was a routine oil change, while the subject of the "best oil" for these engines is often debated, I opted to go with conventional 10w-30 VR1 oil and a Mobile 1 filter. As of the time of writing this post, the engine has responded nicely to this oil and filter and does not make excessive noise, burn, and no new leaks have appeared which has been reported with synthetic oils by other users. I also went ahead and changed the air filter while underneath the hood of the Jeep.
Lastly, while underneath I had noticed one of the transmission cooler lines running to the radiator had began to leak ATF on the pavement. A challenge arose with identifying which hose was the culprit as both were soaked in ATF+4. I elected to just replace both lines with 3/8'' SAE J1532 hoses and replace the worm clamps with a slightly better style hose clamp as I could not locally find constant tension hose clamps in that size. The end result solved the leak and cleaned up on the underside of the radiator quite a bit.
*Note both hoses being soaked in the photo above.
*Final result of the hose repairs.
That's it! 2025 was easily the biggest year for this Jeep given the extensive amount of work done over the course of one year. There is plenty more on this Jeep that I plan to address which includes but is not limited to:
- Restoring the factory half doors and replacing the fabric uppers.
- New springs+pucks (or dedicated 2'' lift shocks)
- Paint correction/new paint
- Cleaning the undercarriage/repainting the frame.
Thank you for reading!
-S.
