The Novak Guide to the

New Process / New Venture Gear Transfer Case Input Gears

np231_transfer_caseNew Process, chain-driven transfer case input gears really warrant their very own topic. There were some forty different variations of them made by NVG.

We've decoded most of the Jeep input gears and many are available for sale. The Jeep 231 transfer case is the main focus of our information here, but these gears interchanges can apply to:

  • NP231
  • NP233
  • NP241 (Chevy, Dodge, Jeep JK)
  • NP242
  • NP243
  • NP246
  • NP247 (always has 23 splines)
  • NP249 (always has 23 splines)

Gears that are not in the same family include:

  • NP203 (gear driven)
  • NP205 (gear driven)
  • NP207 (spur cut gear)
  • NP208, 218, 219, 229
  • NP241OR (always has a short, 23 spline input gear)

Input Gears and Compatibility

Hold on to your seat...

The important variations to look for in the 231 transfer case are in the input gear. The 231 comes in 21 spline and 23 spline versions with long, medium (rare) and short variations.

The long shafts protrude 2.1" from the front mounting face of the transfer case. The short version protrudes 1.2". The rare medium shaft protrudes 1.7". You should be careful when swapping any of these gears due to different bearing widths and gear teeth. The following chart shows how to determine which input gear you might have by transmission. It is always recommended to verify first hand if possible.

  21 Spline 23 Spline
Short Input AW4 (through 1990)
AX4
AX5
Peugeot BA 10/5 (earlier)
30RH
32RH
AX15 
Long Input   TF904 
TF999
Peugeot BA 10/5(later) 
NV3550
NSG370
Medium Input   46RH Jeep ZJ's '93 -'95 
AW4 (post-'90)

Because of differences in the cut of the gear, as a general rule, one should not interchange 1987-1993 gears with 1994-present gears. These years are not always hard and fast delineations. If one is not absolutely certain, disassembly and inspection is required.

Note that some transmissions change spline count. The Peugeot BA10/5 had both 21 or 23 splines. The AW4 had 21 splines through 1990. In 1991 (the same year the 4.0 HO was introduced) the AW4 splines increased to 23.

Be certain, in any interchange situation, that you select the right length of input gear for the factory style transmission being used; e.g., a long input gear against an AX15 (usually requiring a short input gear) will cause interference at the end of the splines and put damaging thrust pressures on the transmission mainshaft and transfer case input gear.

However, if you are using a Novak transfer case adapter assembly, they are engineered to work with both long and short input shafts, though installers will acheive optimum strength spline engagement with the longer input gears.

Anatomy of a New Process Input Gear

231 Input Gear Anatomy

Available 23 Spline Gears

23 Spline Gear

 

23 spline, wide bearing

Short length, wide bearing, early gear cut

23 spline, wide bearing

Medium length, wide bearing, early gear cut

23 spline, wide bearing

Long length, wide bearing, early gear cut

 

23 spline, narrow bearing

Short length, narrow bearing, late gear cut

23 spline, narrow bearing

Long length, narrow bearing, late gear cut

 

 

Available 21 Spline Gears

21 Spline Gear

 

21 spline, wide bearing

Short length, wide bearing, early gear cut

21 spline, narrow bearing

Short length, narrow bearing, late gear cut

Long Style Input Gears 

23 Spline, early


23 Spline, late


Medium Style Input Gears

23 Spline, early


Short Style Input Gears 

23 Spline, early


23 Spline, late


21 Spline, early


21 Spline, late


Torqueflite 42RE Caveat

Unlike all other known transmissions to the Jeep New Process transfer cases, the Torqueflite 42RE transmission as found in 1994 ZJ Grand Cherokees features a unique output shaft with a pilot tip on the end of it. This shaft pilots into the NP input gear in a front-facing caged needle bearing. Note the image below.

We once spoke with an Engineer at NVG. We questioned him as to why there were so many (forty-something) input gear variations in this popular series of planetary-reduction transfer cases. We told him that it was making our lives harder than we'd like. He responded, "Yeah. Isn't it ridiculous?" He went on to mention that he was part of a company committee whose goal it was to cut the number of gears available down to about seventeen versions, instead.

42RE_output_shaft