Gearing Options

 Jeep Wrangler 1987 to Present 

Wrangler transmission Options      Using 2.5L, 4.0L, 4.2L, & various V8s      AX5 upgrades      AX15 5 speed manual      NV3550 5 speed manual      NV4500 5 speed manual      NP435, SM465, SM420, T18 4sds      AW4 4 speed Jeep Automatic      Turbo 350 3 speed automatic      700R4 Overdrive Automatic trans      etc
Wrangler Transfer Case Options      Factory NP231 Tcase Upgrades      Bronco Dana 20 Wrangler application      Atlas Transfer case      Jeep "Rubicon" NVG241OR Tcase
Klune-V Extreme Underdrive Systems      Klune-V/Atlas Combo     "Hercules" Compound Tcase system      Klune-V with Jeep Factory NP231 Tcase      Klune-V with "Rubicon" NVG241OR Tcase      Klune-V / Atlas Combo

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Wrangler transmissions Upgrade Options

The Wrangler usually comes with either a 3 speed automatic (The TF999) or a 5 speed manual. The directions available and how to get there depend on the engine you are using. We have broken this section down by engine type:

      2.5 L Jeep Motor

      AMC 4.0L 4.2L six cyl; AMC V8

      GM V8

      Ford V8

2.5 L Jeep Motor

     Stick Transmisisons

The 4 cyl motor came with the AX5 5 spd trans. This is a light duty trans, and while it is not a bad design, it will not support an engine upgrade. We have had customers desiring to upgrade this trans even with the 2.5L engine. We have packages for the following stick trans conversions:

NV3550 5spd 

The NV3550 is the best manual transmission to come from the factory in a Jeep Wrangler. They have been used from 2000 up. They are strong enough to handle a Chevy 5.7L Vortec motor comfortably. It is about the same size and weight as the earlier Japanese AX15 or the 87-88 French Peugeot trans. It is generally regarded as a major improvement over the Peugeot, and somewhat better than the AX15.  Used in conjunction with a Klune-V Underdrive, you will have all the gearing you will ever need.

NV4500 5 Speed

The NV 4500 is twice the weight of an NV3550. It is basically a truck transmission. It has become very popular among four wheelers due to the fact it combines overdrive, synchronized shifting and deeper gearing in a package that, in a Jeep, is pretty much indestructible.

     Automatic Transmissions

Call us if you have an auto trans project using a 2.5L Jeep motor. We have not researched options for this, however would do so if there is interest.
   

AMC 4.0L 4.2L six cyl; AMC V8

     Stick Transmisisons

Peugeot 5 speed

Manual trans 6 cyl Jeeps 87-88 came with a 5 speed French trans from Peugeot. This trans is not considered to be very reliable, if yours is bad we do not recommend replacing it with another Peugeot.

AX15

From 89-1999 the Japanese made AX15 trans was used. While not considered as reliable as the NV3550, it is a good trans and will hold a mild V8. It does not need to be replaced unless you are converting to a stout V8, or want a tranny with a granny first. Used in conjunction with a Klune-V Underdrive, you will have all the gearing you will ever need

NV3550 5spd 

The NV3550 is the best manual transmission to come from the factory in a Jeep Wrangler. They have been used from 2000 up. They are strong enough to handle a Chevy 5.7L Vortec motor comfortably. It is about the same size and weight as the earlier Japanese AX15 or the 87-88 French Peugeot trans. It is generally regarded as a major improvement over the Peugeot, and somewhat better than the AX15.  Used in conjunction with a Klune-V Underdrive, you will have all the gearing you will ever need.

NV4500 5 Speed

The NV 4500 is twice the weight of an NV3550. It is basically a truck transmission. It has become very popular among four wheelers due to the fact it combines overdrive, synchronized shifting and deeper gearing in a package that, in a Jeep, is pretty much indestructible.

Granny Low 4 spd Trannies

It is also possible to install several variations of the 'Granny Tranny' (A 4speeed trans with extremely wide ratios and "granny" 1st gear. Unless the vehicle will not be used on the highway, we consider the loss of the overdrive to be undesirable. On the other hand, if used strictly off-road, they are less costly and are extremely strong. They are also shorter than the 5speeds. 

     Automatic Transmissions

Link: General Info regarding Auto Trans Conversions

Chrysler 904, Chrysler 999, Chrysler 727

These 3 speed transmissions are all possibilities. High Impact "Bad Boy" versions are available. Variations can be supplied to bolt up directly to AMC/Jeep motors

"Bad Boy" Turbo 350 3 speed automatic

We have the adapters to put a T350 behind an AMC motor, if desired 

"Bad Boy" 700R4 Overdrive Automatic 

If you want to use an automatic, and add overdrive in a wrangler, the most direct way to do it is to use the GM 700R4 trans. Unlike other overdrive automatics, it does not require computer control, it has a first gear about 20% deeper than most other auto trannies, and it can be built very stout (see "Bad Boy 700R4".  With the conversion transfer case adapter AND AMC engine adapter  in place, a 700R4 is about 1.5" longer than the stock Jeep transmission. 

"Bad Boy" Turbo 400 3 speed Automatic

The Turbo 400 is almost always more transmission than needed in a Wrangler, and is kindal long for the space allowed, but if it is needed it can be done. We have Turbo 400s available with AMC engine bolt patterns, and they can be adapted to various transfer cases. call us for details.

GM V8 or V6

Peugeot 5 speed

Manual trans 6 cyl Jeeps 87-88 came with a 5 speed French trans from Peugeot. This trans is not considered to be very reliable, While it can be done, It is probably not worth trying to make it work with a V8.

AX15

From 89-1999 the Japanese made AX15 trans was used. While not considered as reliable as the NV3550, it is a good trans and will hold a mild V8. It does not need to be replaced unless you are converting to a stout V8, or want a tranny with a granny first. Used in conjunction with a Klune-V Underdrive, you will have all the gearing you will ever need

NV3550 5spd 

The NV3550 is the best manual transmission to come from the factory in a Jeep Wrangler. They have been used from 2000 up. They are strong enough to handle a Chevy 5.7L Vortec motor comfortably. It is about the same size and weight as the earlier Japanese AX15 or the 87-88 French Peugeot trans. It is generally regarded as a major improvement over the Peugeot, and somewhat better than the AX15.  Used in conjunction with a Klune-V Underdrive, you will have all the gearing you will ever need.

NV4500 5 Speed

The NV 4500 is twice the weight of an NV3550. It is basically a truck transmission. It has become very popular among four wheelers due to the fact it combines overdrive, synchronized shifting and deeper gearing in a package that, in a Jeep, is pretty much indestructible.

Granny Low 4 spd Trannies

It is also possible to install several variations of the 'Granny Tranny' (A 4speeed trans with extremely wide ratios and "granny" 1st gear. Unless the vehicle will not be used on the highway, we consider the loss of the overdrive to be undesirable. On the other hand, if used strictly off-road, they are less costly and are extremely strong. They are also shorter than the 5speeds. 

     Automatic Transmissions

Link: General Info regarding Auto Trans Conversions

"Bad Boy" Turbo 350 3 speed automatic

 This would be the general purpose 3 speed automatic of choice when using a GM engine and overdrive is not a requirement.

"Bad Boy" 700R4 Overdrive Automatic 

If you want to use an automatic, and have overdrive in a Wrangler, the most direct way to do it is to use the GM 700R4 trans. Unlike other overdrive automatics, it does not require computer control, it has a first gear about 20% deeper than most other auto trannies, and it can be built very stout (see "Bad Boy 700R4".  With the conversion transfer case adapter in place, a 700R4 is about 3/4" longer than the stock Jeep transmission. A 700R4 will of course bolt up directly to a GM engine. 

"Bad Boy" Turbo 400 3 speed Automatic

The Turbo 400 is almost always more transmission than needed in a Wrangler, and is kindal long for the space allowed, but if it is needed it can be done. call us for details.

Ford V8

      (We have done these from time to time, not a real common swap, we have not yet taken the time to write a web section for them. Call regarding Ford V8 applications)

Jeep/Dodge 318 / 5.2 / 5.9L

      (We are familiar with the use of these engines (excellent engines) in Wranglers, however have not taken the time to write up a web section for them yet. Call regarding these V8 applications)

Wrangler Transfer Case Options

All of the Wranglers come with aluminum case, planetary gear, chain drive T-cases. Some of the very early ones used the NP207. All others, except the "Rubicon" edition Wrangler use a NP231. The "Rubicon" edition Jeep uses a  uses a NVG241OR Tcase. 

The NP207 Tcase is fine for stock use, however if it gets tired we suggest replacing it with an appropriate upgrade.

The NP231 is adequate for stock to moderate modified 4WD use. It comes from the factory with a 2.72:1 reduction in low range. This Tcase in factory trim is approximate 21" long, including the output yoke.

Transfer case Upgrades:

   Factory NP231 Tcase Upgrades

There are several upgrades offered for the factory Jeep NP231. We do sell slip yoke eliminator kits. We also offer a Brand New NP231HD. We do not get into the low gear kits or sell HD chain kits separately: Once you begin to add the prices and complexities of installing these kits separately, it becomes more cost effective to buy an Atlas (Call us for special deals and packages on the Atlas)

   NP231HD

This is an all-new transfer-case. It is a custom build, including the extra wide HD chain, slip yoke eliminator (short and extra short versions) and HD 6 gear planetary assembly. If the stock ratio of the 231 is satisfactory for your purposes (or you are using it with a Klune Underdrive) and need a new case, this case has all the goodies and is priced competitively.

   Slip-Yoke Eliminator Kit

For anyone planning to retain the NP231 Tcase and use it off road with more than 4-5" of lift, this is a real good idea. This modification shortens the case as well, to 16-17".

    Wide Chain upgrade

It is possible to modify in a wider chain into the 231. While this makes sense as the chain is a weak link of this Tcase, once you add up the price of 4:1 gears, a SLE kit and a wide chain, you will get more value simply buying an Atlas or Rubicon Tcase

    HD Planetary set

It is also possible to replace the stock gears of the 231 with significantly stronger gears out of an NP241 truck T-case. Usually, however, other parts of a 231 fail before the gears do.

     Atlas Transfer case

An Atlas transfer case is significantly stronger than the stock case. It is a two-speed case, available in four different low range ratios: 3.0. 3.8, 4.3, 5.0. It also features synchronized gears for shifting "on the fly", without needing to stop to change ranges. This case is 13.8" Long, including the yoke

     Bronco Dana 20 Wrangler application

The Bronco Dana 20 case is only 11.7" long including the adapter we supply to bolt it behind a Wrangler transmission. It is an all gear drive case, and is capable of twin stick operation. This case is stronger than the NP231, it is strong enough for all but the most extreme wrangler applications. If the longest possible driveshaft is a requirement, this is perhaps the ways to go. With a Klune Underdrive, it is the total length is still 3" shorter than a stock NP231. We carry these cases.     

     Jeep "Rubicon" NVG241OR Tcase

This is the case that Jeep introduced with the new "Rubicon" edition Jeep Wrangler. It is considerably stronger than a NP231, comes stock with a fixed rear yoke, and has a 4.0 low range ratio. While we do not feel this case is as good as an Atlas, it is a little cheaper

     Ultimate Systems

Why we call these "Ultimate" systems is discussed in detail in the article A Guide to 4WD gearing. 

Klune-V Extreme Underdrive Systems

For Wranglers, in order to accomplish ultimate gearing flexibility, we typically use the Klune-V Extreme Underdrive in conjunction with different transmission and transfer case options. The primary issue in installing such a system in a wrangler is driveline length. The stock trans (auto or stick) is about 24" long from engine block to Tcase. The stock Tcase, including the yoke, is about 21" long. The stock driveshaft is about 15" long. Some variations from year to year, but these are in the ball park generally speaking. 

  Klune-V with Jeep Factory NP231 Tcase

Klune with stock Tcase: A Klune underdrive is 6.5" long. If you convert the output of the stock Tcase to an extra short fixed yoke instead of a slip yoke, and use a CV jointed driveshaft with a Klune installed you end up with about 12.5" of driveshaft. That is about 2" longer than the practical minimum reliable driveshaft, and will work well with up to about 5-6" of lift. There are some tricks to make this work, details are in the Klune/Wrangler install article. This system gets marginal with greater amounts of lift. Dana 44, Ford 9" and Dana60 axle upgrades also tend not to leave enough driveshaft. 700R4 conversions are impractical for the same reason. The solution is the "Hercules"

    "Hercules" Compound T-case system

To come up with the best optimization of gearing while retaining the most driveshaft length possible, High Impact developed a mating of the Klune-V Underdrive with a Dana 20 Tcase out of an early Bronco. This combo, complete is about 3" shorter than the stock NP231, only 1" longer than the NP231 with the fixed output yoke kit installed. We call this the "Hercules" compound transfer case system. With the stock trans and rear axle, the  driveshaft will end up about 18" long. With a NV3550 or NV4500it is about the same. With a 700R4, you have 16.5-17 inches of driveshaft. As you can see, that is plenty even for some pretty radical suspensions and such.      

     Klune-V/Atlas Combo

It is possible to mate an Atlas with a Klune. We usually use the 2.7 ratio Klune in this case with a 3.8 or 4.3 Atlas, so as to be able to get an "Ultimate" spread of available ratios. Using the the Atlas will benefit from the fact that the Atlas has synchronized shifting, and is frankly a better design than the Bronco Dana 20, however it is more expensive and 3" longer. Your call!

     Klune-V with "Rubicon" NVG241OR Tcase

A number of people are coming to the conclusion that a 4.0 low range is too low for some types of four wheeling, such as basic forest service trails or sand dunes. In this case it is possible to ad a 2.7 ratio Klune-V Extreme Underdrive in front of the NVG242OR Tcase. In this manner, both boxes can be put in high for 1:1 high range. The Klune can be put in low with the Rubicon Tcase in Hi, this gives a trail and sand friendly 2.7 low range. Then the Rubicon can be used in its 4.0 low with the Klune in hi, allowing a good 4.0 ratio rock crawling low range. And they can both be put in low 2.7 x 4.0 = almost 11 to one, useful for tricky tight or technical crawling, to get through at an extreme crawl without damage.

Klune Applications with the 2.5L 4cyl engine: This engine can be relocated forward enough to make up the length of the Klune underdrive, leaving the Tcase and drivelines stock.

Klune applications with 4 speed manual transmissions:  if you are using the Klune you will not need the granny first gear. If you are switching to a four speed for length reasons, consider the T176/ It is only 19": long including bellhousing and Tcase adapter, 5" shorter than the stock transmission. The T176 (used in some Jeep CJs in the 80s) is roughly comparable in strength to the NV3550 and will hold a moderate V8.