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Discussion Starter #1 (Edited)
Transfer Cases

The transfer cases used are all chain driven with aluminum housings. NP stands for New Process which is the brand, if you will. The newer ones are NV instead which stands for New Venture. They are the same transfer cases, just under a different name.

NP207: "Command-Trac", Part-Time only, 2.61:1 ratio low
The NP207 has a aluminum case and an appearance similar to the NP231. It should have a tag on the back saying New Process Gear, Model 207. This chain driven transfer case uses a 21 spline input with the manual transmissions and a 23 spline input with the automatic transmissions. The output for the front driveshaft is on the drivers side. Low range is 2.61 and high is 1.00. This transfer case is widely scorned. If yours should break, look for a 21 spline NP231 or swap transmission and transfer case at the same time. The transfer case is upsidedown in the picture showing the input (it is drivers drop.)

Usage
The NP207 was used in the first year of Wranglers in 1987. It was used in Cherokees (XJ) until from '84-'87.​

NP228/NP229:"Selec-Trac"
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.​

NP231: "Command-Trac", Part-Time only, 2.72:1 ratio low
Pattern: 2HI - 4HI - N - 4LO
The NP231 has an aluminum case and it should have a tag on the back saying New Process Gear, Model 231. New versions of the NP231 are refered 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.

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 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.

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.

Usage
Since 1988, the NP231 has been the "Command Trac" transfer case used in Cherokees (XJ), Comanches (MJ), and Wranglers (YJ). It has been the "Command Trac" transfer case in the Grand Cherokee (ZJ) since its introduction. The new Wrangler (TJ) 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 version 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. There is also a 4:1 low range reduction kit for the NP231. Wrangler are only available with "Command Trac", so the NP231 or NP207 are the only transfer cases available from the factory in any Wrangler model.​

NP241: Part-Time, 2.72:1 ratio low
Pattern: 2HI - 4HI - N - 4LO

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
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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 TH350, 4L60E or 700R4 trans, it will be 27 spline. With a TH400 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: "Rock-Trac", 4:1 ratio low

Jeep introduced the NP241OR "Rock-Trac" 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 achieved 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 Turbo Diesel, and is one of the strongest transfer cases factory installed in a Jeep.​


NP242: "Selec-Trac", Full or Part-time, 2.72:1 ratio low
Pattern: 2HI - 4HI (P/T) - 4HI (F/T) - N - 4LO

The NP242 has an aluminum case and it should have a tag on the back saying New Process Gear, Model 242. New versions of the NP242 are refered to as NVG242 or NV242 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.

The chain driven NP242 is a full time transfer case with a 48/52 torque split front and rear. It is possible to lock it into four low so it behaves like a part-time transfer case. When it is locked in, power will be split regardless of traction. The output for the front axle is on the drivers side. Low range is 2.72 and high is 1.00.

Usage
The NP242 is used in Grand Cherokees (ZJ) and Cherokees (XJ).​

NP/NV247: Full-Time
Could not find accurate history, details, or usage other than Jeep Grand Cherokee 1999-2002, popular to swap NP/NV247 with NP242.

NP249: Full-Time
Same as above
 

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Now that I'm in the right thread,I thought that I would point out that you missed the NP249 case.I don't know much about them,other than, I have one in the latest ZJ i bought.
 

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Discussion Starter #3
Ok, updated, but I couldnt really find the history and info on the 247 and 249. If you want to research and add, please do, I'll put it right in the write up!
 

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How would I know if a transfer case (in or out of a vehicle) is bad? The jeep service centers want to charge 120 to take a look at the following: It is a 98' JGC SFI with the V8 and AWD. It has 59,000 miles. On sharp or U turns, there is a pretty rough sound and uncomfortable feel. I will try and provide more info as needed. Thanks!
 

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The chain driven NP242 is a full time transfer case with a 48/52 torque split front and rear. It is possible to lock it into four low so it behaves like a part-time transfer case.
What does that mean?

four low does a 50/50 split? I mean when you put it into 4x4 part time it is a part-time transfer case.
 

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That quote should be revised to say

"It is possible to lock it into Four High or Four Low so that it behaves like a Part-Time transfercase, splitting power equally (50/50) between the front and rear axles."

4Hi and 4Lo are both "part-time" on the NP242, and 4FT is well obviously "Full-Time" (any ground surface - slipper or not).
 

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That quote should be revised to say

"It is possible to lock it into Four High or Four Low so that it behaves like a Part-Time transfercase, splitting power equally (50/50) between the front and rear axles."

4Hi and 4Lo are both "part-time" on the NP242, and 4FT is well obviously "Full-Time" (any ground surface - slipper or not).
Ok good, then the NP242 is 50/50 power split in part-time. I learned something else new! Thanks.
 

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My wife has a 97 zj, had to get the transmission rebuilt. Putting it back in forgot to put the linkage for the t-case back, duhhhh. Now I can't figure out how to get it back in. tried everything but dropping the crossmember to lower everything back down. Any suggestions?
 
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