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After watching your videos I decided to look at a 1998 Jeep TJ Wrangler. My concern since i have no knowledge of the vehicle is how to scrutinize and assure it is a sound vehicle.


Background on the vehicle:


1) The Jeep has a new 2.5 4-cylinder in it, not sure what that means, whether a rebuild or remanufactured?

2) Has 138,000 miles, 5 speed manual no mention in ad of new transmission parts.

3) 1998 black Jeep Wrangler TJ 2.5 with a 5 speed manual with 3,000 miles on the new motor.  New motor put in over the summer (has receipts).
4) 4-inch suspension lift, 1.25 inch JKS body lift+ 1 inch motor mount lift

5) Swing out tire carrier bumper
6) Aftermarket stereo and speakers
7) Aftermarket rims and 31x 10.5 inch tires+ full size spare
8) Aftermarket adjustable track bar
9) Newer shocks and steering stabilizer
10) Aftermarket sway bar links
11) Heavy duty lower front control arms
12) Cold air intake
13) Windshield mounted fog lights
14) Bumper fog lights
15) Custom differential guard
16) Full skid plates
17) Custom lockable center console
18) Tinted turn signals and tail lights (to legal specs.)
19) New water pump, spark plugs, hoses, coolant flush and all new gaskets and seals put in with new motor
20) Hardtop with tint
21) Undercoated frame (prevents rust)
22) Clean title!
23) Paint on hood is chipping a bit but mechanically everything works great.

My last question:  What aftermarket products are critical to inspect for damage? I noticed a MOAB sticker on back window and I'm not very astute or have much knowledge on what to look for!  Any guidance would be greatly appreciated!



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Hi, Papaobewon, thanks for posting your first topic!  You have given us all an excellent opportunity to discuss the concerns around buying a used Jeep TJ Wrangler and aftermarket equipment. 


There are many vehicles out there, as the TJ was extremely popular in its 1997-2006 production period.  I'll describe some things to look at and question regarding this particular Jeep for sale.  My intention is not to berate the vehicle or the individual offering this 1998 TJ Wrangler 2.5L Jeep for sale...


post-1-0-88884400-1374610404_thumb.jpg post-1-0-86270500-1374610516_thumb.jpg

Here are two distinctly different Jeep TJ Wrangler profiles. At left, a hardcore trail runner does what you would expect—drives the hard trails and works the suspension thoroughly! At right, a very clean Jeep TJ Wrangler with hardtop boasts factory and mild aftermarket upgrades—for a very long life expectancy. 


First, let me distinguish that a 2.5L YJ or TJ Wrangler has a different frame than the 4.0L six-cylinder frame.  This is important if you decide that four-cylinder power is "not enough" for the weight or usage you have planned.  With all of the accessories and add-ons that this Jeep features, the 4-cylinder engine is toting quite a package, so fuel efficiency will be only marginally better than a 4.0L six-cylinder model. 


The 2.5L pushrod OHV engine is a great design, AMC's contribution that Chrysler carried forward until the introduction of the 2.4L high-tech engine.  It does a good job when not taxed too much, and the axle gearing is 4.10/4.11:1 on these models with the larger case Dana 35 differential.  


The transmission is an AX5, the lighter version of the AX designs yet with the right gearing for a four-cylinder engine.  Six-cylinder models use the AX15, which does offer a higher torque rating.  To use the AX5 with a six-cylinder engine, you would need an adapter.  If you wanted to make that swap, the YJ or TJ Wrangler changeover involves relocating and building motor mounts because of the frame differences.  (Click on the link to see my MIG welding project.)  This includes differences in the location of the rear transmission mount as well, a lesser fix that involves the skid-plate/crossmember.  For these reasons, it's very important to decide whether you want a four-cylinder versus a six-cylinder model at the onset.


In making that choice, there are a variety of motives.  Some purposely buy a four-cylinder if they plan a V-8 and alternative transmission swap into the Jeep.  Others believe the four-cylinder will get the job done and deliver better fuel efficiency, which it does to a degree—until the weight of the modified vehicle taxes the engine to the point of offsetting the fuel efficiency.


I'd like to draw attention to the performance curves of the 2.5L inline four versus the 4.0L inline six: The four develops its peak torque at a higher rpm, horsepower peaks at 5,400 rpm, a virtually unattainable speed under most driving conditions and surely not fuel efficient at that speed. 


Compare the two engines and transmissions at: http://www.allpar.com/model/cj/specs.html.  This is a 1997 Jeep TJ Wrangler spec readout, the same as the 1998 you're considering.  Also noted is that some base models did not have power steering, I'm presuming this Jeep does?  You need it.


As a footnote, even the 4.0L inline six has a stodgy torque rise in my view, peaking at 2,800 rpm.  By contrast, the legendary 4.2L inline six that contributes its crankshaft to the 4.6L stroker motor build-ups reaches peak torque between 1,600 and 2,000 rpm, depending upon the year model.  That's diesel-type torque and why the 4.6L stroker motor is so popular!


As for the off-road performance of the four-cylinder models, they do quite well.  Gearing in low range makes the engine sufficient for the job, and the MPI (1991-up) version of the 2.5L fuel injection is quite stable in slow crawling. 


I'll address each feature in the order you listed them in your post:


1)  A rebuilt or remanufactured engine should have receipts.  A remanufactured engine is sold as a long block or short block (without rebuilt cylinder head); the complete long block includes the cylinder head and is desired here.  A rebuilt engine should have receipts for machine work as well as parts.  We can discuss the details if receipts are available.


2)  Since this is a four-cylinder model, it has the AX5 transmission as I described.


3)  The description sounds good: a fresh engine, 138,000 miles, only 3,000 on the new engine.  Black is an awkward color, draws heat and tends to oxidize faster.  The peeling or "crazing" is not uncommon for a black vehicle exposed to a lot of sun or parked outside.


4)  A 4-inch lift is common, the body lift is mild as is the motor lift; if done right, this is an asset for off-road use.


5)  Swing-out tire carrier is a plus.


6)  Aftermarket sound is nice if a quality system and installed properly; always concern about wiring during the installation, must be done right.


7)  Tires and spare sound good, 31" is not radical, and the OEM 4.10/4.11 gears can tolerate this diameter tire well.  Speedometer may have slight error if not corrected for the 31" tires, this can be remedied with a speedometer drive gear/tooth count change. 


Note:  It surprises me that there is this much suspension lift plus a body lift for only 31" diameter tires.  A four-inch suspension lift will accommodate 33" tires, which would require a ring-and-pinion gear change to 4.56:1 or even 4.88:1 for restoring performance.  Maybe this vehicle did have 33" tires at one point; otherwise, the combination chassis and body lift is actually excessive for 31" tires. (A two-inch suspension lift would be sufficient for 31" tires on a TJ Wrangler.)  The 31x10.5 tires are likely on 8" rims, and that's really not much track width increase for the amount of lift.  For this amount of lift, I would do a 10" rim with 33" tires to widen the track width and help restore the vehicle's center-of-gravity. 


8)  Adjustable track bar is desirable with a link-and-coil suspension lift.  This allows precise alignment to eliminate axle offset or dog tracking.  Suspension parts and axles need to match up and align when there is an aftermarket lift on link and coil suspension.


9)  New shocks and stabilizer are a plus if "new" means quality replacement parts.  Gas-charged shocks are preferred here, Bilstein or equivalent.


10)  Long sway bar links needed to compensate for the 4-inch suspension lift.


11)  Stronger control arms, if quality made, are a major improvement over the stamped steel OEM arms.


12)  Cold air intake can improve performance.  System should not permit exposure to water, however.  Any open faced air filter should be kept away from the spray or slosh of water during stream crossings!  Sucking water can cause engine hydro-locking and severe internal engine parts damage.


13)  Quality fog lights can be useful for the trail;  make sure they're quality with safe, proper wiring.


14)  Same as windshield lights; great if done properly.


15)  Diff guards are a real plus for off-roading in rocky terrain.


16)  Full skid plates are a plus, too!  This adds weight, though, and we're talking four-cylinder power in this case.


17)  The security console is a real plus, especially when parking the vehicle with the top removed. 


18)  Okay on the tint if legal and visible.  Not sure of the motive.


19)  Receipts useful here.  Quality parts should be verified.  Is the clutch new, too?  Flywheel new or re-surfaced?  Should be included with an engine replacement or rebuild.


20)  Hardtop, especially factory type, is a valuable accessory!  These tops are expensive to purchase later, a hardtop has many advantages: weather protection, security, added value.  Downside is weight, another tax on that 120 horsepower engine.


21)  Undercoated frame can be okay.  Is the vehicle at a climate without salted roads?  If salted, inspect the chassis and body end to end for rust and any signs of body or frame rust exfoliation.  Undercoating is great if applied for the right reasons—not to cover rust, though! 


22)  Clean title is a must...


23)  Chipping paint is back to the black.  If the price is right and you want to restore this vehicle cosmetically, you can do so.


Regarding your last questions, a MOAB sticker can be good or bad.  I've been to Moab since the mid-'nineties and witnessed vehicles used moderately by responsible folks, and I have also seen vehicles pounded mercilessly and abused, even wrecked—often due to driver inexperience.  That said, Moab does mean something—what it means depends upon the driving skill of the owner and which trails the Jeep took at Moab.  The same applies to the Rubicon Trail, Fordyce, Sierra Trek and so forth.


Get underneath and inspect the Jeep end-to-end.  The most critical and expensive areas are the frame and axles.  Look for signs of collision repairs and trail damage, abuse and so forth.  Aftermarket products like lift kits have "perishable" components such as urethane bushings, Heim joints and other pivot points.  Drivelines are a source of trouble, and this Jeep TJ Wrangler should have a slip yoke eliminator (SYE) kit at the transfer case outlet to the rear driveline plus a CV-type rear driveshaft.  If not, the rear driveshaft is at risk;  U-joint life will be short, driveline vibration likely.   


Look for signs of rock-sliding along the control arms and other symptoms of hard use.  Look for scarred diff skid plates.  See if the steering gear is loose by manually moving the pitman arm back and forth with the vehicle parked, its front wheels pointed straight ahead; drive the Jeep and feel for steering wander and suspension looseness.  Signs of trail use are not, in themselves, a reason to pass up the vehicle; however, scarring and looseness do suggest the kind of use the vehicle has seen.


In addition to writing for the 4WD magazines, I wrote for Popular Hot Rodding and several other muscle car and high performance magazines in the 'eighties and 'nineties.  My tech Q&A columns would often receive questions about purchasing a used muscle car or Corvette with "low mileage".  If a muscle car had "only" 50,000 original miles, I would reply that this could potentially be 200 trips down a quarter-mile drag strip!  For a 4WD trail vehicle, 138K miles could be many thousands of trail miles.  Metaphor: The notorious Rubicon Trail is only 12 miles long.  We can "do the math".


Although none of these comments are meant to discourage your purchase, a used trail vehicle is all about its history.  Modified vehicles are typically intended for hard trail use, so you do need to adjust your purchase price to allow for any parts damage from trail pounding.  I would test drive the vehicle with an ear toward axle/differential noises, transmission synchronizer noise and feel (including "jumping out of gear"), clutch and driveline response, plus the drivetrain play and sounds in 4WD low range.


Look closely at the front axle shaft joints in the steering knuckles.  Steering knuckle ball-joints and steering linkage joints can be worn out by this mileage from a lot of trail crawling or oversized tires.  Inspect the front brake calipers and rotors, they're visible.  Look at the drivelines and check for worn U-joints, grease seepage and a torn boot.  A major oil leak at the rear main seal can be a nuisance and ruin a clutch disk.  Axle pinion shaft seals and the transfer case output seals are other areas to check.


Anticipate what you want to do with the Jeep and how the modifications impact your use—or dovetail with it.  Also weigh the cost of outfitting a stone stock 1998 TJ Wrangler with these upgrades.  Consider a stock vehicle with an extraordinary history, something like "driven on icy highways but never off-road," "driven only on graded gravel—occasionally," "used to get back and forth to work in the winter," "used to access a ski resort in the winter," "not sure what this lever position [4WD/low range] does, I've never used it" —fill in the blanks.


My brother-in-law found a 1999 Jeep TJ Wrangler, stone stock with 70K original miles, the auxiliary cloth top never installed, the hardtop never removed, the wheels and tires stock with one OEM tire replacement;  the engine is a 4.0L with 3-speed 32RH automatic transmission—owned by a mature couple, they never went beyond a graded gravel road with the Jeep and used it primarily for basic highway transportation and winter driving.  He paid $6500 for the Jeep.  It is prime for any kind of personalization and modifications, virtually a "new" Jeep TJ Wrangler.


While this sounds extraordinary, it's not a Rubicon model.  For "hardcore" wheeling, the Sport model could use a rear locker.  (Note: Some non-Rubicon TJs actually have the Dana 44 rear axle with limited slip option.)  There would be a need for a lift kit, 4" for 33" diameter tires.  Then all of the other driveline, SYE and other modifications...The cost of parts—and labor if you sublet all of this work—must be considered.


It's not easy making these choices.  The best way to approach this is as an "informed" buyer.  I trust that these comments, the magazine and the forums help.  I and many others can contribute additional comments and ideas, so please ask.  It's for the benefit of everyone!



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Thank You, Sir!

Excellent write-up! I'm a retired Teacher and I can say this article was A+! Your extensive explanation will be my guideline for my Jeep purchase! I will even share this with my friends and family who are interested in purchasing a Jeep like this model! Superb detail and objectivity!

This is by far the best coverage in any forum I have visited for various topics and vehicles! The Old Dog (me) is still learning new tricks!


Papa (obewon)

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Papa, I have lived and breathed Jeep 4WD vehicles for fifty years now and have authored three bestselling Jeep books (Bentley Publishers) that each earned a Mopar official part number.  I still discover new Jeep information and facts! 


I, too, taught, serving as an adult education level automotive/diesel and welding instructor at the Rite of Passage program before advancing to Director of Vocational Training and Site Supervisor of Education...My work with tough young men (often gang affiliated when they entered the program), many eager to learn and dedicate themselves to a productive life through technical training, proved challenging, humbling and, ultimately, highly rewarding.  These students raised the bar for my effectiveness and sense of purpose, and I credit them with making me a better teacher...


Thanks very much for your comments, I value your feedback and am very pleased that the information serves well!  Looking forward to your thoughtful topic posts.



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  • 10 months later...

Dear Mr Ludel,

I took your advice and purchased a 2000 Wrangler TJ Sport! It has a 4.0 liter (based on your advice)

4" Pro Comp Lift and a 32RH Automatic (VIN CHECK @ Dealer to confirm tranny) stock Dana axles, 35 rear, 30 front, 231j Transfer case;

I have No (SYE) Slip Yoke Eliminator installed in the transfer case and want to resolve this issue!

Scenario: buddy has a 2000 Sahara 231j serial #6-16-00 which reflects the manufacture date. My manufacture date was Jan 24 -2000

He has it bolted to a NV3550 (he is willing to sell me the t-Case with the Cardan drive shaft (CV ) and it includes the SYE , we believe but can not confirm that it is an (AA) Advance Adapter kit? I need your advice as I am getting conflicting answers!

My Question: Are the Sahara 231j and My Sport 231j input shafts the same length?

I realize the spline count is 23 for both and my hypothesis is that the extension bolted on the rear of my 32RH may impact the Transfer case Input shaft length!! Our two local 4x4 shops disagree and have conflicting answers, stated below!

Shop A states that both input shafts of the T-Case are exact and that all I need is an AUTOMATIC SEAL EXTENSION that slides over thr Transfer Case shaft to prevent leakage ( currently my 32RH is leaking heavily)!

Shop B - states that input shafts are diiferent lengths and need to be exchanged! ( my Sport input shaft into the SYE Sahara T-Case)

I was told by a local transmission shop that the input shaft was a singular piece ! So my quandry!


I bought an output transmission seal National #710058 but now realize this is NOT an extension seal !

Seal question: is an extension seal also called a Redi-seal?

I also bought a National 3173 T-Case input shaft seal but realize it is not the correct seal ! ( dealer # 5019020AB) going back today!

Help me Mr Ludel youre my only hope!

My main concern is the Transfer Case swap! Any advice would be greatly appreciated!


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For openers, the manual and automatic transmission versions of the 231J are different in 2000 model year.  Each complete transfer case unit has a unique part number.


I know you're academic and can sort through the details of parts distinctions.  The sensible approach is to compare the individual parts you have described, noting the Mopar part numbers for each of these transfer cases and their subassemblies.  Many parts interchange straight across.  Others do not have the same part number, which indicates a difference in design and application.


For your benefit, I have sifted through the Mopar parts catalog covering model year 2000 Jeep TJ Wrangler.  Below are the factory parts illustrations and part numbers for the 231 transfer cases and also the 32RH transmission case and extension housing.  Here are the pages from Mopar's references, you can zoom into the images for details and fit:  


2000 TJ Wrangler Transfer Case Parts.pdf


2000 TJ Wrangler Extension & Cases.pdf


When you seek replacement parts, always begin with identifying the OEM part and its number.  Then you can cross-reference part numbers on items like seals.  Some parts are OEM only while others have an aftermarket counterpart. 


Mopar uses letter codes to identify manual versus automatic transmissions, 4.0L engines versus 2.5L engines, and the chassis and body type for a given model.  Note that these parts listings focus on model year 2000, so this will apply to both the Sahara and Sport models.  This is the resource I rely upon, first generation and from the OE level.



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Thank you Mr Ludel for the information!

I was able to ascertain that the input shafts are of different lengths on the two transfer cases mine being shorter 1.2 versus 1.7 on my colleagues. So I will change my course of action!

If I may ask you about my other concern is the leaking of the 32RH Transmission!

I found the output shaft seal from the information you provided, however, from several sources (Teraflex and other vendors) they refer

To an Extended Output shaft seal ! One source indicated that the OE output shaft seal will NOT seal properly and an EXTENDED seal was utilized by having one machined!

1. How common is this as a solution?

2. Can you make one based on my OE transfer case by catalog? VIN? Yor ?.. is this a hands-on task where it has to be measured?

Again ,

Thank You!

If I can order it from your shop that is what would be my preference!

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Hi, Papaobewon...For that extended seal answer and a detailed explanation of any modifications needed, the best information source would be our friends at Advance Adapters.  They work with both OE and their own Atlas transfer cases.  Since the NP/NV231 is very popular in swaps and for upgrades, any seal issues, improvements and modifications would be addressed by Advance Adapters.


Give them a ring at 1-800-350-2223.  Ask for the tech line, and share that I suggested you call.  They will be very thorough in responding to the seal question, and if there is a needed extension seal, Advance Adapters would know exactly what modifications, if any, are needed. They can also provide any parts.


Should you want to add the SYE to your original transfer case, Advance Adapters would be my choice.



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