Dana 18[edit | edit source]

Dana 20[edit | edit source]

Dana 300[edit | edit source]

Specifications - Model 300 Transfer Case

Transfer Case Type: 4 position, dual range part time 4 wheel drive unti with integral low range.

Torque Transmittal Mode: Constant mesh gearbox with layshaft gear arrangement.

Low Range Reduction Ratio: 2.6:1 gear reduction.

Drive Positions and Shift Controls: 2H, 4H, 4L and Neutral. Ranges selected via floor mounted shift lever. 4H and 4L ranges are undifferentiated.

Case Configuration: One piece cast iron with aluminum front/rear bearing caps.

Lubricant Capacity and Type: 4 pints (1.9 liters) SAE 85W-90 gear lubricant API grade GL-5.

Torque Specifications Model 300 Transfer Case, listed using USA Foot Pounds / (Metric Newton Meters):

Bottom Cover Bolts: 15 / (20)

Cover Plate Bolts: 35 / (47)

Front Bearing Cap Bolts: 35 / (47)

Front/Rear Yoke Locknuts: 120 / (163)

Input Shaft Support Screws: 10 / (14)

Lockplate Bolt: 23 / (31)

Shift Fork Setscrews: 14 / (19)

All torque values given in foot-pounds and (newton meters) with dry fits unless otherwise specified.

NP200[edit | edit source]

The NP200 was used in the Military WC 61-63. It is a 6x6 Tcase with 3 Outputshafts and a drumbrake on the Straight rear output.

It is gear driven and bullet proof.

NP207[edit | edit source]

"The NP 207 is one of the weaker Jeep transfer cases, but can be upgraded. The NP 207 has an aluminum case and chain driven planetary reduction. Thankfully the NP 207 was installed behind some of the weakest Jeep power trains every used. It featured a 2.60:1 low range and a straight through design high range, but featured a driver side front output. It was used in one year of the Jeep YJ Wrangler in 1987, and in the early XJ Cherokee's from 1984-1987."

NP228/229[edit | edit source]

The NP228/229 transfer cases were Jeeps first transfer cases to receive the "Selec Trac" name, the later Selec Trac transfer case being the NP242. Both the NP228 and NP229 offer 2 wheel drive, Full Time 4 wheel drive in High range and Part Time 4 wheel drive in Low range. The NP228 uses an open differential for its front/rear power split in 4WD Fulltime High, the NP229 uses viscous coupling for its front/rear split in 4WD Fulltime High. Both lock the front/rear output shafts in 4 wheel drive in Low range. Both lack a 4 wheel drive Part Time High range mode.

The NP228 was offered in '85-'87 XJ Cherokees.

The NP228/229 use 2 controls for its various modes. A vacuum switch controls 2 wheel drive or 4 wheel drive. A shift lever controls High or Low range.

NP228/229 Selec Trac features:[edit | edit source]

  • 2 wheel drive - for all road conditions.
  • 4 wheel drive full time high - for all road conditions including dry pavement.
  • Neutral - disengages front and rear driveshafts.
  • 4 wheel drive part time low - for *off road* conditions with low traction conditions and extra pulling power is needed. NOT FOR USE ON DRY PAVEMENT as transfer case damage may result.

NP231[edit | edit source]

Overview[edit | edit source]

A medium Duty part-time transfer case, the np231 features shift on-the-fly 4hi, a good lo range, and massive aftermarket support. Cast in aluminum, the case should have a tag on the back saying New Process Gear (or New Venture Gear), Model 231. New versions of the NP231 are referred to as NVG231 or NV231 which stands for New Venture Gear. The tag on the back of the transfer case will reflect the name change. Only the name is different. A NV231 HD model is used in some ZJs. Presumably this is a "heavy duty" version for Jeeps with the big V8s, which features a wider chain and corresponding sprockets etc.

There are versions of this chain driven transfer case that take 21 and 23 spline input shafts. The 23 spline version is used behind the AX-15 and NV3550. The 21 spline is used behind the AX-5 and the BA-10/5. The output for the front driveshaft is on the drivers side. Low range is 2.72 and high is 1.00.

Tech tips[edit | edit source]

If you own a 21 spline NP231 and you want to swap in a 23 spline transmission, you can either look for a cheap 23 spline NP231 at the junk yard or go to your local Jeep Parts Dealer and order up a new input shaft part #5300-6085. This is the part you need to convert your NP231 to 23 spline input.

Model number explanation[edit | edit source]

Sankar K. Mohan of New Venture Gear defined what the numbers on their T-cases mean:

The first number is the number of speeds:

  • "1" = one speed (high range). Example – the NV 136.
  • "2" = two speeds (high range and low range). Example – the NV 231.

The second number is the strength:

  • The NV 231 is designated "3" in strength, not as heavy duty as their largest T-cases, which go up to a "7" (eg, NV 273, for vehicles with a GVW of 17,500 lb).

The third number designates the type of T-case:

  • "1" = part-time 4WD
  • "2" = full-time 4WD with an open center differential plus lockable part-time option – like the Selec-Trac NV 242 of the Jeep Cherokee and Dodge Durango, or the Hummer’s NV 242HD AMG.
  • "3" = electrically shifted.
  • "4" = not currently used.
  • "5" = Torsen-type differential.
  • "6" = computer controlled multi-plate wet clutch, like GM’s AutoTrac NV 246.
  • "7" = GeroDisc – like the Grand Cherokee’s Quadra-Trac II NV 247.
  • "8" = not currently used.
  • "9" = viscous coupling.

Usage[edit | edit source]

Since 1988, the NP231 has been the "Command Trac" transfer case used in the XJ Cherokee, MJ Comanche, and YJ Wrangler. It has been the "Command Trac" transfer case in the ZJ Grand Cherokee since its introduction. The new TJ Wrangler continues to use the NP231, but the NP231 used in the TJ has a different tail housing that allows the removal of the drive shaft with out losing transfer case fluid.

Both versions of the NP231 used in the Wranglers have an over all length that is long for a short wheel base vehicle. This can cause driveline vibration and premature u-joint failure especially for a lifted vehicle. There are kits to convert the tail housing to a standard yoke to allow the use of a longer rear drive shaft. The kit is called a SYE (slip yoke eliminator), it is recommended to get one when going with more than 4" of lift on the wrangler models (although in some cases modifications are needed in as little as 2" of lift, but in that small of a lift you can get by with a transfercase drop). The SYE kit is available as a standard fixed yoke or a super short shaft kit. Short shaft kits cost a bit more but allow you to run a longer driveshaft to decrease driveline vibes, and therefore allowing you to have more lift. There is also a 4:1 low range reduction and a "2 lo" (allows you to drive in 2wd but in your low range setting) kit for the NP231. Wranglers are only available with "Command Trac", so the NP231 or NP207 (the NP241 in rubicons)are the only transfer cases available from the factory in any Wrangler model.

Operation[edit | edit source]

Using the 231 is straight forward. During normal operation on road the shifter will be in the 2-hi possition. The operator may shift into 4-hi while driving if the situation requires more traction. Shifting into 4-lo may only be done once the vehicle is stopped or moving slowly and the clutch is engaged. While in 4-lo, vehicle speed must not exceed 40 MPH. When shifting back to 4-hi or 2-hi from 4-lo the vehicle must be stopped or moving slowly and the clutch is engaged. It has been suggested that after shifting from 4-lo to 4-hi, the vehicle should be driven in reverse for a short bit to fully disengage out of 4-lo.

links[edit | edit source]

Source: http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=260351

Technical Info[edit | edit source]

NV 231 Specs
Hi-Range Ratio 1:1
Lo-Range Ratio 2.72:1
Drive Type Chain
Case Material Cast Aluminum
Shift pattern 2-hi | 4-hi | N | 4-lo
Shift on the fly Yes (4-hi up to ~45mph)
Dry weight ~75 lbs
Oil capacity 2 Quarts
Rated GVW Please contribute here
Input shaft spline count 21 & 23

NP241[edit | edit source]

"Starting in about 1987, the New Process 231/241 series transfer case became standard in Jeep, Dodge, and Chevrolet applications. These transfer cases are part time 4WD (Shift positions 4HI - 2HI - N - 4L). They have a relatively thin aluminum housing. They are 1:1 direct drive in high range, and use planetary reduction gears for low range with a ratio of 2.72:1 They use chain drive for the front output. The NP241 was typically used in V8 applications.

Exact identification:

These New Process cases have a circular plate, about 2" in dia., on the rear of the case, in the center. Full identification info for the case is on this plate Bolt Pattern:

Jeep, Dodge and Chevy versions all use a 6 bolt circular bolt pattern. This pattern is NOT symmetrical and will only bolt up one way. You can typically bolt a Jeep unit to a Dodge transmission and vice versa, however Chevrolet units are NOT cross compatible: While GM uses the same 6 bolt patter, they have it rotate approximately 90 degrees from that used by jeep dodge.

In all of these 6 bolt applications the Klune-V Extreme Underdrive will bolt up to these transfer cases directly with adapters necessary. Some may require a spacer. Slip-Yoke Eliminator

All of these units we have seen have been equipped with a slip-yoke rear output. Slip-Yoke Eliminator kits are available for most of these transfer cases Jeep / Dodge units:

All of these cases have a left hand drop (front drive shaft on driver's side).

Input Spline: most applications use a 23 spline female input shaft .

There are a few Dodge 1 Ton or greater extra-HD 241s that use a 29 spline, but they are quite rare. GM New Process 241 Transfer Case

In 1988, GM began using the NP241 transfer cases. Most of these units will be right hand drop, but Chevy also used a few left hand drop applications. 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 or 5 speed, it will be 32 spline.

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."

NP241OR[edit | edit source]

New Process 241 OR "RockTrac" Transfer Case

Jeep introduced the NP 241OR RockTrac transfer case in the Rubicon package in the TJ (and continued it in JK) Jeep Wrangler. The NP241OR has a 4:1 low gear ratio acheived through planetary reduction.

The NP241OR is only available with the Rubicon trim level in the Wrangler TJ and Wrangler JK.

The transfer case was originally designed to withstand the torque output of the Cummins Diesel, and is one of the strongest transmissions factory installed in a Jeep.

NP242[edit | edit source]

Offered in XJ Cherokee, ZJ Grand Cherokee, WJ Grand Cherokee and KJ Liberty. Shift pattern: 2WD - 4 PARTTIME - 4 FULLTIME - N - 4 LO. It is an aluminum case with chain drive and can use a center differential for its front/rear power split or lock the shafts together depending on mode. Uses Dexron III ATF fluid.

It has a 2.72:1 low range and offers 2WD, 4WD Part-time, 4WD Full-time, Neutral & 4WD Low. The 2WD and 4WD Full Time options may be used on any road surface including dry pavement. The 4WD Part Time and 4WD Low may only be used on slick, low traction surfaces such as snow, sand, dirt, gravel and such. It is an "on the fly" transfer case allowing shifts between 2WD, Fulltime 4WD and Parttime 4WD at speed up to 55 MPH. 4WD Lo is handled differently, see below.

Selec-Trac Features:[edit | edit source]

  • Either 2 or full-time 4-wheel drive in HI range;
  • A N (Neutral) position to disengage the axles from the powertrain
  • Part time four-wheel drive in Hi or Lo range.

Select either 2-wheel drive (2WD), full time 4-wheel drive (4 FULLTIME) or part time 4 wheel drive (4 PART TIME) by moving the shift lever to desired mode. Mode selection can be made *WHILE THE VEHICLE IS MOVING AT ANY SPEED UP TO 55 MPH.*

  • 2WD or 4WD Full Time (2WD or 4 FULLTIME) - In either position, the vehicle may be operated on all road surfaces. In 4WD Full Time, Select Trac offers better traction when roads are wet, snow covered or icy. Use Selec-Trac 4WD Fulltime year-round (full time) if you wish. Comparable to what other vehicles call "all wheel drive."
  • N Position (Neutral)- In this position the axles are disengaged from the powertrain. The vehicle may be towed without removing the propeller shafts. Place an automatic transmission in Park or a manual transmission in gear after the N position is engaged.
  • 4WD Part Time High Position (4 PARTTIME) - This position provides 4WD for occasional use in low traction driving conditions such as snow, dirt etc. NOT FOR USE ON DRY PAVEMENT as transfer case damage may result.
  • 4WD Lo Position (4 LO) - This position provides 4WD for occasional use when *OFF-ROAD* driving conditions require low speed pulling power. NOT FOR USE ON DRY PAVEMENT as transfer case damage may result.

NV247[edit | edit source]

Offered in the WJ Grand Cherokee, known as Quadra-trac II.  Shifting positions are 4 All time-N-4 low.  Ditches the viscious coupling used in the 249, instead uses a Gerator pump, which uses special transfer case fluid to deliver power front to rear, 0-100 percent torque to each axle.  This was also used in the Quadra-Drive systems, which also utilized Vari-lock differentials front and back, Jeep’s version of a limited slip differential (LSD).

NP249[edit | edit source]

Offered ZJ Grand Cherokee. Shift pattern: 4 HIGH - N - 4 LO. It is an aluminum case with chain drive and can use a center differential for its front/rear power split or lock the shafts together depending on mode. Under normal driving conditions most torque is applied to rear axles but when slippage is detected a georotor pump engages a disc clutch to route power to the front axles. All NP249/NV249 transfer cases after 1996 the Low range is gear driving 50/50 to front and rear axles. When coupled with Jeeps Vari-Loc axles the entire system is called Quadra-Drive instead of Quadra-Trac II. Uses Dexron III ATF fluid.

This full time four wheel drive system offers a neutral and low range (2.72:1).4WD Full-time, Neutral & 4WD Low.

Quadra-Trac Features:[edit | edit source]

  • Either Fulltime 4 Wheel High or Fulltime 4 Wheel Low ranges
  • Split power to front & rear on demand as slip occurs
  • Available on ZJ as Quadra-Trac

The NV 249 can be problematic and expensive to repair and is not one of the most popular transfer cases. Many times Jeepers prefer to replace this with either a NP242 or NP231

Viscous Coupling Failure:[edit | edit source]

The main symptom of Viscous Coupling (VC) failure include chirping or spinning of the front tires during sharp slow turns on pavement where you would not expect any chirping.

Since the VC is a sealed unit and does NOT operate using the fluids withing the transfer case, changing the fluids within the case will NOT fix the problem. Changing the fluids will, however aid in keeping the rest of the transfer case in good shape.

Heat buildup inside the VC is both what can destroy it and what operates it. Whenever the speed of the front and rear drive shafts do not match perfectly, the plates inside the VC are slipping in the internal fluids, creating heat. Minimizing that heat is the key to long life.

One common tool to diagnose failure is to drive the vehicle in tight figure 8's if it hops or chirps, there is a high probability that the Viscous is in need of replacement

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