Klune-V Applications Manual

By the time you are reading this, we figure you have probably discovered that an Extreme Underdrive is the most flexible way to go, giving the most gearing options with the least likelihood of breakage.

You have a concern: It does look like it may take a bit of doing to actually install one, and get it all dialed in just right. That's true. Some applications are actually pretty easy, and a few will take some doing. Is it worth it? That's up to you to decide. But first, you gotta know what you're really going to be up against. We prepared this technical manual to help you visualize exactly what it will take to get Extreme Underdrive into your trail rig.

Basic Information (common to all installations)

"David" and "Goliath" Models

Warranty

Detailed Technical Applications data

No-Adapter needed direct bolt up applications

Issues regarding input shaft compatibility

Underdrive works in any position

Shifter Options

Divorced Tcase and 2WD applications

Do I need to move the Tcase back?

Driveline Geometry

Crossmember and mounting issues

The Klune V "Foot Mount" mounting bracket

Klune-V/Transfer case interface data, listed by transfer case

Will I need a spacer: Long and Short input shaft

An Extreme Underdrive is an underdrive gearbox that bolts in place between the transmission and transfer case. We call it "Extreme", because the underdrive multiplies your existing gear reduction by up to 4 times, rather than a usual underdrive of 1.2 times, or so. It is intended for extreme four wheel drive applications, rather than towing or gear splitting in a big truck. It works equally well with both manual and automatic transmissions.

The David crawler 4:1 gearset is rated at 2500 ft/lbs input torque. It is intended primarily for short wheelbase applications where extreme low crawl gears are desired for moving very slowly and precisely through difficult or very tight rock formations, and up or down waterfall type obstacles. The emphasis is on precision, skill and finesse. While plenty stout, it is geared too low to be practical for hammer down, tire-spin applications. (If you need more tire speed, simply shift the David into 1:1 ratio, leaving your transfer case in low range).

Both units are physically the same size, and have the same bolt pattern. These units are new-manufactured, purpose built units, which come with a full one year warranty. While similar to "Dual transfer case" units in function, they are not built up from cut or sectioned used transfer cases.

The following topics discuss detailed technical aspects of Klune-V Extreme Underdrive applications. It is a broad treatment of the subject: It is intended to supply the needed information to understand the factors involved in installing an Extreme Underdrive in a very wide variety of applications, from common to total custom. Klune-V application engineers are available to discuss your application with you in detail at 800-222-3619. We update our website with new information as we learn it: klunev.com.

The "standard bolt pattern" designed into the Klune-V Extreme Underdrive is the most common bolt pattern used on American made transfer cases. It is a 6 bolt circular pattern, used on all New Process 231, 241, 208, 207, 242, 249 Transfer cases. One or another of these cases are used in almost all Jeep, Dodge, Ford, and Chevy 4WD vehicles since 1987. This bolt pattern is used on 1986 and later Chevrolet NP205s. It is used on the Jeep Dana 300 case. It is used on the Ford and Dodge NP205s. It is also used on most of the Borg-Warner transfer cases used in late model Fords.

If your rig has one of these, or one of many other transfer cases that use the same bolt pattern, the bolts will line up between the transmission and transfer case without further adapters. Other applications, such as Dana 18/Dana 20, or early Chevy NP205 T-cases, will require adapters. Adapters are available from Klune-V for many possible combinations.

These are all a Female input, designed to directly accept a Jeep/Dodge 21 or 23 spline or Ford 31 spline transmission output shaft.

The "Goliath" (2.7 to one) Model Extreme Underdrive is currently available with:

These are all a Female input, designed to directly accept a matching male transmission output shaft.

In the case where we do not have an input gear to match your transmission output shaft, there are many adapters available. Contact Klune-V or your Klune-V dealer. Output shafts are available for both "David" and "Goliath" models in 21, 23, 27, 31 and 32 spline. 6 spline output shafts for use with the Jeep/Scout Dana 18/20 transfer case, Ford "Early Bronco" Dana 20. 10 spline female shafts for use with early Chevy 205 cases are also now in production.

Klune-V Extreme Underdrive Works in Any Position

While many Chevy, Dodge, Ford and Jeep vehicles use the same basic transfer case bolt pattern, Jeep/Dodge, Ford and Chevy have them rotated, or "clocked" differently from each other. The Klune-V Extreme Underdrive is cylindrical in shape, and doesn't care in what direction it is rotated. We have designed the unit in such a way that it can be configured to mate properly with any combination of these clockings. (See clocking drawings in appendix). The unit has provisions to clock the t-case up for improved ground clearance.

It is also possible to assemble the Klune-V Extreme Underdrive with the shifter mechanism installed in 2 possible locations. The unused location then becomes an inspection plate location. (See drawings in appendix, to clarify this). In this manner, the shift mechanism can be oriented so as to not conflict with existing components, and may be oriented in the best location for your specific application.

The Klune-V Extreme Underdrive can be built with yoke input and/or yoke output. In most American divorced transfer case applications, it is possible to install an appropriate adapter on your transmission, and install the Klune-V Extreme Underdrive onto the transmission. For this application, the Klune-V Extreme Underdrive is supplied with a yoke output. A short intermediate drive shaft is then used between the Underdrive and the transfer case. In other applications, it is possible to mount the Crawler to the T-case, or to operate the Crawler entirely divorced.

Pre-Engineered Kits for Specific Applications

Call us for Klune-V application articles on specific application kits we have developed, such as for the Jeep Wrangler, Suzuki Samurai, and the Ford Early Bronco. Check our website or call us, as we may have developed more Application Kits since this writing.

Do I need to move the transfer case back?

The basic Klune-V Extreme Underdrive is 6.5 inches long. In most vehicles, this will mean moving the transfer case back. In many vehicles, no adapters are required, or the stock adapter is suitable. In these vehicles, the Crawler will bolt directly in between the transmission (or original adapter) and transfer case. In this case, the transfer case setback will be 6.5".

Note: In some cases, it is necessary to use a short spacer or an adapter after the Crawl Box in order to clear parts of the transfer case. These are usually 1 inch long. See specific information for your transfer case (below) for this data.

Use a shorter adapter

In some applications, the stock application used an adapter between the transmission and transfer case. There is often an available replacement adapter that is much shorter than the original, offering a considerable length savings.

Example: In one Ford application we did, the vehicle came with an NP435 Transmission and an NP205 8.75 inches long. We replaced the adapter with a shorter one 4.25" long.

The Underdrive in this case requires a 1" spacer in order to clear the T-case shift linkage on the Ford NP205 T-case. Thus, in this example, the amount we had to move the transfer case was:

Moving the Engine Forward

In some cases it is possible and more desirable to move the engine forward. A noted example of this is the four cylinder Jeep Wrangler. The motor can move forward, thus keeping the stock T-case location necessitating no driveline cutting or modification.

Driveline Geometry

Since installation of a Klune-V Extreme Underdrive frequently affects drive shaft length, it is important that we mention the issue of driveline geometry in this manual. One of the things we have noticed, is where people are having trouble with their drive shafts, they do not have the geometry set up correctly. Even in longer drive shafts, if certain angle relationships are not observed, vibration and binding may result. Longer drive shafts are more forgiving of geometry error.

Short (10-15") drive shafts want to have the driveline geometry set up correctly.

Generally speaking, for short drive shafts, the preferred drive shaft consists of a CV joint at the rear yoke of the transfer case, a slip joint mid shaft, with a single U-joint at the differential end of the drive shaft. The differential is rotated so that the pinion shaft of the differential is pointed straight at the center of the output yoke of the transfer case. The angle at ride height which the CV joint operates as well as the maximum angle at full droop of the suspension is important.

Geometry Notes: For proper geometry, a drive shaft using simply 2 U-joints should have the U-joints operating at equal and opposite angles., as shown in the example to the right. In other words, the pinion shaft should point in a direction parallel to the output shaft of the T-case. In this way vibration cancellation is maximized. When you use a CV joint, vibration is cancelled in the CV joint itself. Thus, you want the lower U-joint operating at close to zero degrees nominal. This U-joint imparts no vibration, then, and all of the angle is carried by the CV joint.

Our technical consultants are available to help in this area. Also, we have had experience working with several good drive shaft houses who are quite knowledgeable in this area whom we can refer. The Extreme Underdrive is bolted in place between the transmission and the T-case. This moves the T-case back 6.5". A Slip-yoke eliminator kit is installed in the rear of the stock T-case. This gains back 4 inches. In this manner, the rear yoke of the T-case is moved back 6.5-4=2.5 inches. A new drive shaft is built with a CV joint and a slip joint in the shaft, at the new length of 13 inches. The rear axle assembly is rotated about 14 degrees, raising the pinion yoke (Note "Geometry Notes" below). This reduces the driveline angle, and improves operating geometry at the same time. This arrangement will give better driveline geometry than the original, even though it is about 2.5" shorter. Note the angle the stock shaft has it's U-joints operating at: about 22 degrees. Now note the angle the U-joints in the new shaft work at: the rear one stays at zero while the CV joint U-joints see about 7 degrees each. Click here to see larger version of the Jeep Driveline Drawing.

Cross Member and Mounting Issues

Usually, one of two methods are used for mounting and support.

Existing Rear-of-Transmission or Transmission Adapter Mount

In many cases, it is possible to use the existing mount under the rear of the tranny, or on the transmission adapter. The only drawback to this method is that, with the Klune-V Extreme Underdrive installed, the weight of the transfer case is suspended out pretty far behind the mount. With no support at the transfer case, there is concern that the weight of the T-case, when going over a large bump or drop, may tear the mounting bolts out or crack the transmission or adapter case. We have been successful in bolting an additional piece of steel channel or tubing between the frame rails behind the T-case, and mounting a rubber or urethane snubber under the tail housing or appropriate location on the transfer case. This snubber is mounted up in contact with, but not pushing on the T-case. When a bump is encountered, the transmission mount compresses slightly under the load, and the weight of the transfer case is supported by the snubber.

Clockable Jeep-Dodge-Ford

Mount.

Mount with notch for Chevy 205 Linkage.

The Klune-V Extreme Underdrive “Mounting Foot”

In some applications, it is preferable to not use the transmission or transmission adapter mounting locations at all. A steel "mounting foot", available from Klune-V, can be bolted in with the Crawler. Then the original cross member is re-located farther back on the frame rails, or a new crossmember is fabricated and bolted up to the frame rails. A rubber mount such as a GM transmission mount or a Jeep rubber transmission support should be used between the Mounting Foot and the Crossmember. In this case, the rear snubber is not necessary.

Transfer Case Information

Detailed information is provided in this regarding mating a Klune-V Extreme underdrive to specific transfer cases.

Jeep New Process 207, 208, 231, 241, 242 and 249 Transfer Cases

Bolt Pattern:

In all of these applications the Klune-V Extreme Underdrive will bolt up between the transfer case and transmission directly with no further adapters necessary. All of these New Process Cases use the same bolt pattern as the Klune-V Extreme Underdrive, and have Jeep/Dodge bolt pattern clocking. All of these cases have a left hand drop (front drive shaft on driver's side).

Input Spline:

These T-cases come with either a 21 or 23 spline female input. The 21 spline shaft is usually found in 4 cylinder applications and the 2.8L, V6. 4.0L 6 and 8 cylinder vehicles usually used the 23 spline input gear.

21 Spline input: Due to the torque multiplication of the Klune-V Extreme Underdrive, we consider use of the 21 spline shaft between the Klune-V Extreme Underdrive and the transfer case to be marginal. We do make a 21 spline output shaft for the Klune-V Extreme Underdrive. If you have a 21 spline shaft, this is fine to go from the transmission into the input of the Klune-V Extreme Underdrive. It is recommended however, for maximum strength, to change the input gear on your transfer case to 23 spline.

In many cases, we can supply these input gears. We will need to know the year and model of the transfer case.

Transfer Case Shifter

In most cases the stock transfer case shifter can be retained in the stock location. The linkage rod will need to be extended. This is done by cutting the existing rod in the middle, slipping an appropriate length of steel tubing over the ends of the cut pieces, and welding in place.

Wrangler NP231 Applications

Wranglers will need to have a fixed yoke adapter installed on the back of the NP231 transfer case. This saves about 4" of drive shaft in YJs and TJs . This then causes the rear drive shaft to only need to be shortened minimally. It is then possible to install a new drive shaft with a CV joint and a slip-spline. This arrangement is much better than stock.

Transmission Bolt-Up

Transmissions that originally bolted up to any of these T-cases will also bolt directly to the Klune-V Extreme Underdrive. The crawler can be supplied with the correct 21 or 23 spline input gear in this case. This input will properly mate up to your
existing 21 or 23 spline transmission or adapter output.

In some cases, the stock adapter may be replaced with a shorter NP231 adapter. This will reduce the net setback of the transfer case.

Jeep Dana 300

From 1980-1986 Jeep CJs used Dana 300 transfer cases. Jeep Dana 300s have a right hand drop (front drive shaft on the passenger side). They have the same circular bolt pattern found on the Klune-V Extreme Underdrive. No adapter is required to bolt the Klune-V Extreme Underdrive to the Jeep Dana 300. A 1" spacer is required in order for the rear of the crawler housing to clear the input bearing retainer and seal of the Dana 300. A ¾ inch spacer is also available for use with the mounting foot to add up to the required 1" spacing.

The Jeep Dana 300 has a 23 spline internal (female) input. The Klune-V Extreme Underdrive for this application is thus supplied with a 23 spline (male) output shaft.

Transfer Case Shifter

We have available a twin stick shifter that is fairly universal in Jeep/Scout Dana 300/Dana 20 Extreme Underdrive applications. It will exit the floorboards near where the stock T-case shifter came out. This type of shifter will allow front wheel drive, rear wheel drive or 4WD in any gear range.

Use of the original shifter is usually pretty straight forward. These cases typically came with shifters mounted to the front of the case. While there are a number of variations, we have not found any that will not work with the Crawler in place. Some require minor modification. Unmodified, the shifter will exit the floorboards to the rear of where it originally came out. Alternately, the shifter can be modified or a different shifter installed that will have
longer control rods and will exit at or near the stock location.

Transmission Bolt-Up

Transmissions that originally bolted up to a Dana 300 will also bolt directly to the Klune-V Extreme Underdrive. The crawler is supplied with a 23 spline internal, long style input gear in this case. This input will properly mate up to your existing 23 spline transmission or adapter output shaft, and will properly interface with the oil seal provided.

In some cases, the stock adapter may be replaced with a shorter NP231 adapter. This will reduce the net setback of the transfer case.

Jeep/Scout Dana 18/20

Jeeps used a Dana-Spicer 18 or 20 transfer case from 1941 to 1979. These cases all had the same bolt pattern, also shared with Scout. An adapter plate is required to bolt a Klune-V Extreme Underdrive to these transfer cases. These cases all had a right hand drop (front drive shaft on the right, or passenger side of the vehicle).

The Dana 18 can be identified easily, as its rear output is offset down and to the passenger side (directly behind the front output yoke). This makes this case a possible replacement for Toyota Land Cruiser cases, which have the same rear output configuration. The Dana 20 has its rear output yoke directly behind the input, in the center of the vehicle.

Indexing

The front indexing hole on these cases have either a "Large Hole" (4") or a "Small Hole" (3 1/8"). The small hole was used when mated to a T84 or T90 transmission. All other Jeep cases had a large hole. The Klune-V Extreme Underdrive adapter plate used is the same for both; a stock T90 bearing retainer is used with the small hole while a stock T86 retainer is used with the large hole case. A new #307 sealed bearing is recommended with either of these retainers. In this installation, net setback of the transfer case is 7.5 inches.

Input Shaft

Most of these cases originally had the input gear carried directly on the output shaft of the transmission, and the case did not have an input shaft. This gear usually had a 6 spline internal configuration, and was secured to the transmission shaft by a nut on a threaded portion at the end of the shaft.

The Klune-V Extreme Underdrive main shaft used in this application is a one piece shaft, and has the same six spline, threaded end, configuration.

The notable exceptions are:

1969 - 1971 Jeeps with the T14 transmission used a 10 spline shaft. In this case, it is necessary to replace the input gear with the equivalent tooth-count 6 spline version.

The 70's Jeeps with Turbo 400 automatics had a 32 spline output shaft and used a spud shaft in an adapter housing. The input gear is carried on the spud shaft, and is not compatible with the six spline version. In this case, you must replace the input gear with the 6 spline version.

Transmission Bolt-Up

In vehicles with transmissions that originally bolted to a Dana 18 or 20, it is necessary to install or change the adapter on the transmission. This in some cases will involve replacement of the transmission main shaft. Replacement of the existing adapter housing or addition of an adapter housing on the rear of the transmission will be involved.

Alternately: A transmission may be used that is set up to bolt up to a Jeep Dana 300, NP231, 241, 242, and the remainder of this family of cases, e.g. T176 or T5.

Transfer Case Shifter

See Jeep Dana 300: Same data.

Transmission Support/Cross Member

The Dana 18/20 adapter is used with the universal foot mount to hold a GM style trans mount. This places the mounting point directly in front of the transfer case, where it will provide best support for the trans-Crawler-transfer case setup. The crossmember will need to be relocated farther back on the frame rails, a new crossmember fabricated, or in the case of a skid plate, the skid plate drilled further to the rear to bolt up the mount.

Scout Dana 20

The transfer case adaptation requirements are the same as the Jeep Dana 20.

Scout Dana 300

Scout Dana 300 Transfer Cases did not use the same bolt pattern as the Jeep Dana 300. They use the same bolt pattern as the Jeep Dana 20. The input gear is similar in that it bolts to the transmission output shaft, but it is a 23 spline rather than a 6 spline. It is necessary to replace the Scout input gear with the Jeep 6 spline input gear of the same tooth count. We can help with this. This done, Our Dana 18/20 adapter will bolt the crawler up to your Scout D300.

Early Bronco 66-77 Dana 20

The Dana 20 used in the early Bronco 66-77 has a different bolt pattern, and has a left hand drop. It also has a different input shaft configuration. Thus, adapting to it has different factors. We offer an adapter. to mate the Klune V to this transfer case.

GM New Process 205 Transfer Case

The NP205 gear driven transfer case is considered by many to be the king of bullet proof. It was supplied in many GM, Ford and Dodge trucks. GM 205s have a right hand drop.

These cases used an 8 bolt, sort of oval bolt pattern. These units require a ¾ inch thick (intended for use with the mounting foot, ¼ inch thick) adapter plate to interface with the Klune-V Extreme Underdrive.

Input Spline: We have run into three different input spline configurations on these cases.

1986 and Later GM NP205

These units use the standard 6 bolt circular pattern, with a Chevy clocking of the pattern, and have a 32 spline female input. This boltpattern is directly compatible with the Klune-V Extreme Underdrive The 32 spl shaft is available in a long (appx 2-3" stickout) or short version (appx 1-2"stickout). With the short version, A spacing of 1" is required in order to clear shift mechanism movement. This spacing is obtained by use of a 3/4" ($75) spacer in conjunction with the ¼ inch thick mounting foot.($75). The long 32spl input would require an additional 1" spacer. These spacers have a clearance notch machined into them to clear the shift rail.

A 32 spline output shaft in the Klune-V Extreme Underdrive is provided for this application..

Ford New Process 205 Transfer Case

The Ford NP205 transfer case uses the same 6 bolt circular bolt pattern as our crawler, with the Ford clocking of this pattern. It has a left hand drop. It is customarily supplied with a 31 spline female input. The Klune-V Extreme Underdrive will bolt up directly to this unit. A spacing of 1" is required in order to clear shift mechanism movement. This spacing is obtained by use of a 3/4" spacer in conjunction with the ¼ inch thick mounting foot. These parts have a clearance notch machined into them to clear the shift rail.

This may be used with a stock Ford adapter that was originally intended for use with a Ford NP205 or Ford NP208 Transfer case. The Factory shifter should work fine, only requiring that the linkage rod be extended. Alternately, a shorter unit designed for Jeep applications may be used with some modifications. The stock shifter can be used as in above. A mounting bracket must be fabricated. A right angle bracket can be made out of a 1.5 inch section of angle iron. A rib of the adapter can be drilled, as well as this bracket. The bracket is then bolted to the adapter, and the shifter is mounted to this bracket.

The GM NP203 T-case requires an adapter plate to be used. The unit shown has a 32 spline female input. This is directly compatible, as are 10 spline units. 27 spline units will need to be converted.

Ford New Process 203 Transfer Case

This box will have the 6 bolt circular pattern and should be a 31 spline female input and is direct bolt up.

Dodge New Process 203 Transfer Case

This T-case will have the 6 bolt circular pattern and should have 23 spline female input and is a direct bolt up.

GM NP208 Transfer Case

In 1981 through 1987, the NP 208 transfer case was used in many GM vehicles. It has a low range reduction ratio of 2.6 to one and a right hand drop. This case has the same 6 bolt circular pattern as the Klune-V Extreme Underdrive. It was supplied with a 27 spline female input or a 32 spline female input. The Klune-V Extreme Underdrive will bolt up directly in these applications; It is necessary to specify whether your NP208 case has the 27 or 32 spline input. The Crawler can then be supplied with the correct output spline. This case is a planetary reduction, chain drive part time four wheel drive unit.

Ford NP208 Transfer Case

This T-case will have the 6 bolt circular pattern and should be a 31 spline female input. This unit requires a spacer, but is otherwise a direct bolt up.

Dodge NP208 Transfer Case

This T-case will have the 6 bolt circular pattern and should be a 23 spline female input. This unit requires a spacer, but is otherwise a direct bolt up.

GM New Process 231/241 Transfer Case

In 1988, GM began using the NP231/241 transfer cases. They have a low range reduction ratio of 2.72 to one, use planetary reduction gears, and are a chain drive part time four wheel drive unit. This case has the same 6 bolt circular pattern as the Klune-V Extreme Underdrive. The Chevy NP231 is supplied with a 27 spline female input. The Chevy NP241 is supplied with a 27 spline female input or a 32 spline female input. With a T350, 4L60E or 700R4 tranny, it will be 27 spline. With a T400 or 4L80E trans, it will be 32 spline. The Klune-V Extreme Underdrive will bolt up directly between the transmission adapter and the transfer case in these applications; It is necessary to specify whether your transfer case has the 27 or 32 spline input. The Crawler can then be supplied with the correct output spline. In some cases adapters are available that are shorter in length than the original unit. Measure the length of your adapter and consult the table of transmission adapters.

Dodge NP 231/241 transfer cases have a low range reduction ratio of 2.72 to 1, use planetary reduction gears, and are a chain drive, part time four wheel drive unit. This case has the same 6 bolt circular pattern as the Klune-V Extreme Underdrive. The Dodge NP231/NP241 is normally supplied with a 23 spline female input. (There are a few 1 Ton or greater extra-HD 241s that use a 29 spline, but they are rare). The Klune-V Extreme Underdrive will bolt up directly between the transmission adapter and the transfer case in these 23 spline applications. At the time of this writing, Klune-V does not support the rare 29 spline application.

Ford Late Model Borg Warner Transfer Cases

Various Borg Warner Cases were used in most recent model Ford 4WD vehicles. Most of these were built using a six bolt circular bolt pattern, and have a 31 spline female input shaft. Klune -V makes a Planetary Crawler to directly fit these 6 bolt circular pattern, 31 spline applications. There were a few models that used a 5 bolt pattern. This can easily be determined simply by getting under the vehicle and looking. At the time of this writing, Klune-V does not have an output housing plate to support bolt-up to these units. Contact us if you need one; we may have one available by then.

Some of these cases, such as in the Bronco II, used a 25 spline input. At the time of this writing, Klune-V does not have an output shaft to support bolt-up to these units. Contact us if you need one; we may have one available by then.

Advance Adapters Atlas Transfer Case

The Advance Adapters Atlas transfer case is a well designed, strong unit available in a left or right hand drop. This after market case is available in 3.8:1 ratio or a 4.3 to 1. The Klune-V Extreme Underdrive bolts up directly to the Atlas Transfer case.

Shaft compatibility: As the Atlas is available with many different input spline configurations, it is only necessary to select one that is compatible with an available output shaft for the Klune-V Extreme Underdrive. If you are buying the Atlas new, we suggest the 32 spline input, as it
is the biggest.

The Atlas T-cases are also available with different bolt patterns: You will want the 6 bolt circular pattern, as discussed above. We would recommend the Klune-V Extreme Underdrive "Goliath" 2.73 to 1 ratio. This will give you an easy low range that you won't otherwise have with the Atlas, for easy stuff like sand or hill climbs. And it will still let you have the atlas 4.3 to 1. Plus it will give you extreme killer low range of 2.73 x 4.3 = 11.74 to one. The 4:1 David will bolt up and work fine, if you feel those gear ratios are more suited to your needs.

Table of Contents

Basic Information (common to all installations)