NP 231 Transfer Case Rebuild Kits and Parts

Are you having problems with your NP231 transfer case and need a rebuild kit or replacement parts?  We offer quality professional 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 a 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 usually used in 4 and 6 cylinder Jeep, Dodge and Chevy applications.
Chevrolet NP231 Transfer Case Parts  Dodge NP231D Transfer Case Parts Jeep NP231J Transfer Case Parts  Transfer Case NP231 Drawing & Parts List
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 your tag located on the rear of your unit for a 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 factory tolerances are maintained. All units are tested at the factory prior to shipment.  Troubleshooting problems .

 NP 231 Transfer Case Rebuild Kits and Parts Products 





New Process Model 231 231 Transfer Case Illustration Exploded View to assist you in part identification and assembly.
Part-Time Transfer Case Vacuum Shift 231 Transfer Case Saver $49.29 will not work on 3 bolt trail housing units
GMC / Chevrolet T-Series 1988-97 / Jeep XJ, YJ and TJ 1986-On / Dodge Dakota 1988- On Recommended fluid for NP231 -- ATF





DTS-BK231 Rebuilder Kit - Bearings, Gaskets, Seals,  & Pads .940"/24mm wide BD50-8 input Brg. (GM, Dodge, Jeep)  
DTS-BK231A Rebuilder Kit - Bearings, Gaskets, Seals & Pads .630/16mm wide 6010-N input Brg. (GM, Dodge)  
DTS-BK231J Rebuilder Kit - Bearings, Gaskets, Seals & Pads .630/16mm wide input Brg. (Jeep except Liberty)  
DTS-BK231JA Rebuilder Kit - Bearings, Gaskets, Seals & Pads .630/16mm wide input Brg. (Jeep Liberty)  
TRS-TSK231 Overhaul Kit - Gaskets, O' Rings and Seals (except Jeep)


TRS-TSK231J Overhaul Kit - Gaskets, O' Rings and Seals (Jeep except Liberty)  
TRS-TSK231JA Overhaul Kit - Gaskets, O' Rings and Seals (Jeep Liberty)  
TC-Saver Transfer Case Saver don't leave home without it, stop premature failure See installation instructions  
201207C Adapter to Transfer Case Gasket Chevy / GMC


TRS-351001  Small Parts Kit    
201049 Adapter Housing Seal (trans side) Jeep / Dodge - Not in Kits


201032 Input Gear Seal - Double-Lip Chevy / GMC


201050 Input Gear Seal Jeep / Dodge


201040 Front Output Shaft Seal 38mm I.D. Chevy/GMC/Jeep/Dodge


201040A Front Output Shaft Seal 28mm I.D. Chevy/GMC


45551B Rear Output Shaft Seal 27 Spline Output shaft Chevy/GMC


34743A Rear Output Shaft Seal 32 Spline Output shaft Chevy/GMC


12925D Rear Output Shaft Seal 2.563" I.D. 2.372" O.D. Jeep / Dodge


45551B Rear Output Shaft Seal 1.500" I.D. 2.372" O.D. Jeep / Dodge


201040J Rear Output Shaft Seal 2.584" O.D. (Not in Kits) Jeep / Dodge


TRS-351334 Range Fork Bushing (Plastic)    
TRS-44066 Extension Housing Bushing 1.5" O.D. Chevy / GM


TRS-12066 Extension Housing Bushing 1.510" O. D. 26 & 27 Spline Dodge


TRS-331066 Extension Housing Bushing  32 Spline  


201501 Input Ball Bearing BD50-8


201506 Input Ball Bearing 6010N


TRS-351670 Input Shaft 21 Spline 4 1/8" Jeep w/.940 wide input bearing    
TRS-361670A Input Shaft 23 Spline 4 1/4" Dodge w/.940 wide input bearing    
TRS-371670B Input Shaft 23 Spline 5 1/8" w/.940 wide input bearing    
TRS-352670CC Input Shaft 23 Spline 5 1/8" w/.630 wide input bearing    
TRS-351672 Main Shaft 26 Spline 18 3/8" Dodge Call & see if we have a good take out shaft, save money  
TRS-321840K Fork Pad Kit  


TRS-352849A Range Fork - #16976 or 17833 Aluminum Update


TRS-352850A Mode Fork (iron) Cast #16196    
TRS-351850 Mode Fork 30 Teeth (Late Dodge)    
TRS-351645K Range Slider & Hub  


TRS-351646 Mode Slider 24 Teeth    
TRS-351701K Mode Assembly (complete)    
TRS-351701 Mode Syncro 48 Teeth    camra.jpg  
TRS-351701A Mode Syncro 60 Teeth    
TRS-352646B Mode Slider 30 Teeth     
TRS-351500 Oil Pump Assembly    
TRS-351588A Planet (6 Pinion) used w/.630" wide #6010-N Bearing 1994-Up Call and see if we have a good take out unit to save money.  
TRS-351588 Planet (6 Pinion) used w/.940" wide #BD50-8 Input Bearing 1987-94  Call and see if we have a good take out unit to save money.  
TRS-321411B Switch, Vacuum 4 prong black  
TRS-321411 Switch, Vacuum 3 prong black  
TRS-351760-1 Case Half Front Cast #16118 Call and see if we have a good take out unit to save money.   
TRS-351760-2 Case Half Rear Call and see if we have a good take out unit to save money.  
TRS-351772 Tail Housing 5 3/4" Cast #16354 Call and see if we have a good take out unit to save money.   
TRS-351806 Driven Sprocket (1.25" wide chain)    
TRS-HV-027 Drive Chain -  62 Pins, 1/2" Pitch, Round Pin 1.0" Wide - 36 Links


TRS-HV-022 Drive Chain -  62 Pins, 1/2" Pitch, Round Pins 1.25" Wide - 31 Links


MTC Heavy duty upgrade Sprocket (Set) and Chain    
TRX231 Book on CD Rom, Troubleshooting & Overhaul Guide    


Illustrationclick to enlarge


np231syncro48teeth.jpg NP231 Syncor Ring



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 happening because in sand high 4 works fine but when trying to climb up steep hills in 4-low the rear wheels spin and the front doesn't subscribe.

Troubleshoot by: It could have 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.