NP 231 Transfer Case Rebuild Kits and Parts

Having problems with your NP231 transfer case, need parts?  We offer quality profession rebuilt NP231 transfer cases and parts including rebuild parts kits that are designed to be top of the line overhaul kits.  The New Process 231 series transfer case started to be installed in Jeep, Dodge, and Chevrolet applications in 1987.  These transfer cases are part time four wheel drive with shift positions 4HI - 2HI - N - 4L. The NP231 is 1:1 direct drive in high range, and use planetary reduction gears for low range with a ratio of 2.72:1.

 

This unit is chain driven front output, left hand drop (front drive shaft on driver's side) on the Jeep and Dodge, while GM had right hand drop and even a few with drive side drop. The 231 are a light duty transfer case typically used in 4 and 6 cylinder Jeep, Dodge and Chevy applications.

 

 

 

 

 

 

 

 

 

 

 

These New Process cases have a circular tag on the rear of the case, near the center close to where the rear drive shaft exits. Identification information for the NP231 transfer case is on this tag typically includes model number, assembly number, and serial number and ratio data. When ordering a replacement transfer case it?s most important to provide the assembly number. This number is typically eight digits, four number a rivet/screw head and four additional numbers.

Jeep, Dodge and Chevy versions all use a 6-bolt circular bolt pattern. This pattern is non-symmetrical and will only bolt up one way. Jeep units and Dodge units are general interchangeable, however Chevrolet units are not. While GM uses the same 6-bolt patter, they have it rotate approximately 90 degrees from that used by Jeep or Dodge.

NP231 transfer cases come with either a 21 or 23 spline female input. The 21 spline shaft is frequently found in 4 cylinder applications and the 2.8L V6, While 4.0L 6 cylinder and 8 cylinder applications always used the 23 spline input shaft. The GM/Chevy NP231 is supplied with a 27-spline female input

A cross reference table is provide to assist you in identification of your transfer case. Check tag located on rear of unit for model number. An illustrated drawing is provide below to assist you in parts identification, ordering and assembly. Back to other model transfer case parts availability page, sometimes we can supply good used take out parts to save you money. Don't see what you need just give us a call toll free 800-216-1632..  If you decide to replace your NP 207 transfer case with a remaufactued unit with a 12 month warranty see our complete list of transfer cases for Chevrolet/GMC, Dodge and Jeep vehicles. All rebuilt transfer case get new seals, bearings, chains, fork pad, encoder motors and viscous couplers.  All shafts, slider, hubs and planets are inspect to ensure proper tolerances are maintained. All units are tested at the factory prior to shipment.  Troubleshooting problems .

Troubleshooting:

I have a Jeep Cheroke Sport 1994 4.0lt. Problem: our wheel drive works fine in 4 high but in 4 low front axle does not engage ino this is hapaning because in sand high 4 worksfine but when trying to climb up steep hills in 4low the rear wheels spin and the front don"t subscribe.

Troubleshoot by: It has to be something to do with the shift cam/4wd switch. It can be checked by jacking the vehicle up off all four wheels and while in 4L seeing if the front driveshaft is turning while in 4L if the shaft isn’t turning it is defiantly a transfer case problem, if the shaft is turning and the front tire or tires are not it is in the switch that is suppose to turn on the accuator and engage the differential.