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Jeep Buying Forum FAQ

This thread is designed to help future Jeep owners better educate themselves before buying a Jeep. I have asked various questions to various distinguished JeepForum members with the intention of getting those particular members expertise in one centralized location. This thread will be a continuously updated thread that, hopefully over time, will become a very useful tool. As it stands right now this FAQ thread isn’t 100% done but is close enough to be published. The participating members have volunteered their time to benefit the members of JeepForum, so I encourage all members to take a look at this FAQ as there is some extremely valuable information included.

Let me explain how this FAQ works. I have generated questions that a lot of future Jeep owners may ask before purchasing a Jeep. Then I asked the various questions to JeepForum members with specific knowledge on that topic so we could get the most accurate answers possible. Each post below contains one specific members question(s) and responses, which are quoted. Below that I may or may not include feedback of my own.

Directory To The FAQ
General Jeep Questions
Wrangler FAQ
Cherokee FAQ
Grand Cherokee FAQ
Various Stock Axle Options
Jeep Buying Links



If you feel a specific question/information should be added to this FAQ please feel free to PM myself with your ideas and I will add the information accordingly.

-Kyle

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The following was written by member igofshn whom is a very knowledgeable member in regards to wranglers. He has been a dedicated member of JeepForum since 2001.


What are the main differences between the YJ, TJ, and JK?

The YJ was a redesign of the older CJ. It was named the Wrangler. Brought out in 1987 and ran through 1995. It is basically the same size as a CJ7 but it has square headlights. the TJ was a redesign of the YJ in 1997 and incorporated coil springs and went back to the round headlights. There was no 1996 Jeep wrangler. the ride of the TJ is significantly better than that of the YJ. In 2003 Jeep came out with another version of the TJ, the Rubicon. The Rubicon has 4-1 transfer case and 4.10 gears. the JK is a redesign of the TJ, it is significantly bigger than the TJ and is also available with 4 doors. the redesign was started in 2007 and continues today. The name wrangler is still associated with the design.

The following was written by Bryson whom is a knowledgeable JeepForum member and specializes in motors. Currently he is working on a remote mounted turbo kits which is expected to be ready by summer of 2008. He has been a dedicated member since 2005.

What are the differences between the 2.5L 4cyl and the 4.0L 6cyl motor. Why should i get one over the other?

The main difference between the 2.5L and 4.0L power plants is power. Obviously the 4.0L has much more torque than the smaller 2.5L 4 cylinder, but the overall power band is different as well.

The 2.5L has a typical 4 cylinder power band in that the power will continually rise past idle up to about 5k or so before tapering off. Most 4 cylinders will need to be revved to get the power out of them due to typical rod/stroke ratios.

In terms of gas mileage, the 2.5L is less than impressive. From my personal experience, the 2.5L jeep will average around 16-22mpg. Considering that most 4.0L jeeps will get around 15-20mpg, going with the smaller motor really won't save much at the pump. But no one should really choose a jeep if they are looking for fuel economy. The main determinant in that after all is drag, and Cherokee is not much better than a school bus. If your going spend your hard earned money, get a 4.0L.

The 4.0L however has a very "small block" like torque output in that the motor makes peak torque right off of idle. This is one of the reasons why the motor has been so popular. Also just like the small block V8, these motors are insanely simple. With an almost prehistoric pushrod design, the 4.0 is very easy to work on. Really, the only advances AMC had developed into the engines have been the fuel injection systems. They are also much more abundant compared to the 2.5L, so finding parts for them is very easy and inexpensive.

[XJK]

Wrangler Section Place Holder


Here are some additional links that will be helpful in regards to the Wrangler YJ, TJ, and JK.
Jeep Wrangler YJ FAQ's
Jeep Wrangler YJ Wiki
Jeep Wrangler TJ Stock Specifications
Jeep Wrangler TJ FAQ's
Jeep Wrangler TJ Wiki
Jeep Wrangler JK FAQ's
Jeep Wrangler JK Wiki

[XJK]

The following was written by member balloo93 whom is a moderator of the JeepForum Cherokee section. He has been a dedicated member since 2002 and a moderator since 2004.


Why should I buy a XJ?

The XJ celebrated a VERY long and successful run with Chrysler. It was the first small SUV on the market and it's cost and versatility made for a very popular vehicle. The pros and cons can be laid out as such:

Pros:
Lightweight
Mid sized wheelbase makes it maneuverable
Lots of junk yard parts available
Compatibility between years for swapping parts
Aftermarket support
Cost

Cons:
Unibody

So the only downfall of the XJ is the unibody. While on a mildly built rig this wouldn't be much of an issue, when 33" tires or bigger come to play the unibody will need to be braced. Bigger axle swaps also mean more reinforcement of the stock suspension and body. The XJ's popularity has brought about many options for doing this very thing. Weld in kits, home fabricated braces, and stiffeners abound. Rocker protection selection is also quite diverse and makes for many choices for the owner.

The XJ's AW4 trans is a stout unit as well. If a Aux cooler is added or a rig is factory equipped with one, the trans will generally last a long time. Many of the other Jeeps transmission available were problematic and not as strong.

The XJ's transfer cases options were also quite good. The NP231 and NP242 of the 87+ years are great platforms. While there is not as much aftermarket support for the NP242, every year there seems to be more. The NP242 is superior to some of the other optioned transfer cases out there and often are swapped in place of those units (ie NP249 to NP242 swaps in grand Cherokees). The NP231 is a great unit across the Jeep platform. It's tried and true performance spills over into the GM market as well. The aftermarket support is strong for this cases and offers many options for improvement.

Th XJ's High Pinion D30 84-99 was also a strong point. The one piece axles of the 92+ (also 87-91 NP242 equipped XJs) make for a strong setup and a platform that can be easily modified to be even stronger. The earlier ABS equipped and the 95+ XJ D30's use the bigger X297 Ujoints and these can stand up 33" tires. The verese rotation and high pinion design make for a stronger front axe in general. The Low Pinion D30 from 00-01 isn't necessarily a bad axle, just not as strong as the HP units.

The XJ has had various rear axles under it sense it's start. The options were:

D35 without the C-clipped 27 spline axle shafts
D35C with Cclips (91-01) 27 spline shafts
Chrysler 8.25 with 27 spline shafts
Chrysler 8.25 with 29 spline shafts

D44 optioned form 87-90 (87 was the most prominent year) with 30 spline axle shafts
The D44 is the preferred stock option for it's strength, 30 spline axle shafts, and aftermarket support. The Chrysler 8.25 with 29spline axles is the second strongest factory option. The 8.25 with 27splines and the D35non c-clipped share equal strength. The D35C tends to be the low man on the totem pole.

The 8.25 housing is quite strong and it's nearly 3" axle tubes are not prone to flex. It has a larger (8.25") ring gear and D60 sized pinion shaft. The D35 axle tubes tend to flex and this is what tends to lead to most failures. Any of the above axles will bolt up with the differences being that you can't run ABS on a 8.25 or D44 and that a like equipped driveshaft must be used sinse the pinion lengths are different between the different axles.

What years are the best?

The question of which year to buy comes up often. Truth be told, it will depend on what your intentions are for the vehicle. I will cover over some pros and cons for each year:
84-86
Pros:
Usually can be had quite cheap

Cons:
Body welds notorious for coming apart
Under powered carberated engines with the exception of the 86 4cyl that was EFI
Transmissions were decent, but no Overdrive
Transfer cases are not the most desirable, and finding parts for them nearly impossible

Overview:
These can be had quite cheap. With work the 2.8L GM V6 can be made to run reliably, but it requires a lot of upkeep in the form of vac lines and many parts are no longer available for them. Not many aftermarket parts for them either. If you can find one cheap and score a GM 3.4L V6, swap that in and run that. Lots of online info on that swap.

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87-90

Pros:
First years of the 4.0L Renix engines
Optional D44 is a great axle right out of the box
Manual Trans options were mixed, but the AX15 is a good unit. The BA5/10 is not as desirable
AW4 trans a solid unit with an Aux cooler installed, also optioned with Power/Comfort switch for towing
Fairly easy to troubleshoot with a voltmeter
Quite a bit of support from the aftermarket
ABS equipped units used x297 Ujoints on the front axle shafts
Single O2 sensor

Cons:
The Renix system does not store codes. It requires a bit more work to diagnose problems
Power output was 177hp. Still has a good balance of weight to power
D35 more prominent
The BA5/10 manual trans is not as desirable
Two piece D30 axle shafts with CAD set up can be problematic (vacuum line failure)
Single diaphram brake booster
Closed cooling system requires some maint to keep it tip top

Overview:
These years are good years for owners that aren't afraid to get thier hands dirty and know how to use a volt meter. They are pretty common and can be had on the cheap. Can be easily built to be a good daily driver and offroader. Aftermarket has a decent amount of support as well. Some of the weak point sof these years can be upgraded with newer model year parts. These older systems tend to react better to performance upgrades without error codes being thrown or sensor freaking out.

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91-94

Pros:
Intro of the HO engines and management with 190hp (91-00)
From 92+ the two piece CAD D30 axles were replaced with one piece axles
OBDI systems allowed for self diagnostic and stored codes
Simplicity of Open Cooling system
Intro of the 8.25 axle (stronger housing and axle tubes)
Single O2 sensor

Cons:
Non ABS D30s used X260 Ujoints
8.25 rear axle used 27spline shafts

Overview:
These years are great for entry level shade tree mechanics for a good daily driver or offroader. Plenty of aftermarket support. Most weak parts can be swapped out very simply (example- dual diaphram booster from a 95-96 swap right in). HO TB easy to mod to 60mm. Single O2 sensor makes for cheaper up keep and less complicated.

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95-96

Pros:
Used a dual diaphram brake booster
Used the X297 as standard equipment on all D30's
Late build 96 8.25 axle may have the 29 spline shafts
96 OBDII system allowed for scanners

Cons:
Many sensors were swapped between these years and it makes getting the right one a PITA

Overview:
These years are great for intry level shade tree mechanics for a good daily driver or offroader. Plenty of aftermarket support. Most weak parts can be swapped out very simply. HO TB easy to mod to 60mm. Single O2 sensor makes for cheaper up keep and less complicated.

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97-99

Pros:
Out of the box stronger front and rear axles (D30 front and 8.25 rear)
Can be had for reasonable prices
Some have lower miles on the Odo
Transfer cases used sealed output slip yoke housings
99 Intro of the equal length intake manifold
Cup Holders on center console
97 was intro of metal rear hatch

Cons:
Generally more susceptible to driveline vibration when lifted
Dual O2 can be expensive if overhauling
99+ used different hubs and rotors not a problem, but something to be aware of

Overview:
Great beginners vehicles with the stronger axles you can comfortably run 33's locked.

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00-01

Pros:
Same as the 97-99
NV3550 manual trans has lot of aftermarket support
Can be had with low miles on the Odo
Saw a 3hp increase to 193hp

Cons:
Same as the 97-99
Low pinion D30

Overview:
Great beginners vehicles with the stronger axles you can comfortably run 33's locked. It's usually recommended to swap to the HP D30 front axle.

Here are some additional links that will be helpful in regards to the Cherokee XJ.
Jeep Cherokee XJ Stock Specs
Technical Links
Jeep Cherokee XJ Wiki

[XJK]

The following was written by member ArloGuthroJeep whom is a moderator of the Grand Cherokee section. He has been a dedicated member since 2005 and a moderator since 2007.


Why should I buy a Grand Cherokee?

Cargo space, comfort & luxury items, various engine & transfer case options. Some people enjoy the full-time 4wd options and not having to think about which 4wd mode to put it in. Other enjoy the wide variety of control you have with the NP242 (Selec-Trac) transfer case. They are unique to mod - it isn't very frequent you see another modified ZJ/WJ compared to a CJ/YJ/TJ/XJ.

Reason’s not to buy a Grand Cherokee:
Don't buy them to tow your other trail rig - they aren't heavy enough. Don't buy them and try and modify them cheaply - everything on them is expensive and since they have "luxury" items, they have a lot more that can go wrong with them, then say a TJ/XJ.

What are the main differences between the ZJ and WJ?

Aside from looks, they are very similar. In the suspension department the WJ is minorly better. They both have 5-links up front (4 control arms and a trackbar). The WJ has a stronger steering box mounting location compared to the ZJ. In the rear the ZJ had a 5-link. The WJ has a 3-link (wishbone upper control arm) eliminating the rear trackbar.

The ZJ mounts the spare tire on the inside which takes up cargo space, the WJ has it built into the floor.

What motor option should I go for and why?

Generally speaking, get the biggest engine you can. The 4.0, 4.7, and 4.7HO are all available in the WJ and are good engines - however the WJ is heavier then the ZJ so the 4.0 is slightly underpowered.
The 4.0, 5.2, and 5.9 are all available in the ZJ and good engines. The 5.9 is a beast - they are the envy of all ZJ owners.

For rock wheeling it doesn't matter. In mud/snow/sand you want more power so get one of the V8's.

What transfercase option should I go for and why?

The ZJ's NP249 Full-Time (Quadra-Trac) Transfer Case has a VC (Viscous Coupler) which can go bad (notable by the wheels hopping/gripping when turning, especially tight turns when the TC has warmed up). The WJ's NP247 Full-Time (Quadra-Trac II) Transfer Case has a PC (Progressive Coupler) that can go bad (notable by it not sending power to the front at all). The PC is generally better then the VC since the PC shared fluid with the rest of the TC so it is more serviceable then the VC. Early variations of the 249 TC (93-95) didn't lock themselves in 4-low and still relied on the VC to transfer power front and rear. 96-98 the TC was locked when in 4-low.

The Command-Trac (NP231) was available in ZJ's only and the Selec-Trac (NP242) was available in ZJ's and WJ's. My personal preference in the 242 because I DD my WJ, it gives me two advantages. The first is when driving on patchy snow/ice I can drive in a 4wd mode and not worry about stressing my drivetrain. The second is when a rear Aussie Locker (auto-locker), driving in full-time makes the locker completely transparent. Compared to the 2wd mode of the 231, or the full-time modes of the 247 and 249 (which send power to the rear only until slippage is detected) that make the locker lock up and chirp/unload going around corners if you give it gas around a corner.

Here are some additional links that will helpful in regards to the Grand Cherokee ZJ/WJ.
Jeep Grand Cherokee FAQ's
Jeep Grand Cherokee ZJ Wiki
Jeep Grand Cherokee WJ Wiki

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Various Axle Options

*Front Stock Axles
Dana 30


Information:
http://www.jeepforum.com/wiki/index.php/Dana_30


*Rear Stock Axles
Dana 35


Information:
http://www.jeepforum.com/wiki/index.php/Dana_35


Chrysler 8.25


Information:
http://www.jeepforum.com/wiki/index.php/Chrysler_8.25


Dana 44


Information:
http://www.jeepforum.com/wiki/index.php/Dana_44

[XJK]

Here are some good links if you are interested in buying a Jeep.

How much should I pay for a Jeep?

www.kbb.com
www.nada.com (more accurate for what finance companies use than kbb in today's market)
www.edmunds.com
www.carprices.com
www.pricequotes.com


Where should I buy my Jeep from?

www.craigslist.org
www.ebay.com
www.carmax.com
www.autotrader.com
www.autoweb.com
www.autofinder.com


I would also suggest searching through local papers and of course take a look at dealerships for the rare deals that they provide.

-Kyle