Stock T-Case Guide
NP207
Usage: 1984-1987 Jeep Cherokee, 1987 Jeep Wrangler
Notes: Chain-driven unit with aluminum case, used both 21- and 23-spline input shafts, drivers-side front drop, 2.61:1 low range.
Weaknesses: Many. Factory slip yoke is excessively long and prone to failure and leakage. Weak case, low gear ratio is lacking.
Strengths: None. Replace with NP231 for best results.
NP231 transfer cases' can...
NP231 transfer cases' can be trusted for difficult to extreme trail use but it fairs much better when equipped with any of the available popular upgrades. The unit shown uses a JB Conversions Super Short SYE. This alone is enough to greatly enhance its trail prowess and reliability but the Tera Low231 half case with 4.0:1 low gears lends it even greater capability.
NP231
Usage: Jeep Wrangler YJ (1988-1995), TJ (1997-2006), and JK (2007-present), Cherokee, and Grand Cherokee.
Notes: Chain-driven unit with aluminum case, also known as Command-Trac. Uses both 21- and 23-spline input shaft spline counts in short, medium, and long shaft lengths. Driver's side front output, centered rear output. Planetary gear sets use a three-pinion assembly.
Weaknesses: Factory slip yoke is excessively long and prone to failure and leakage. Factory 2.72:1 low gear ratio is somewhat high for extreme usage. Shifter is problematic and tends to slip out of gear. No 2WD low ability.
Strengths: Versatility and parts availability. When outfit with a SYE the NP231 is a sturdy 'case. It's even better with 4:1 low gearing. This is a great T-case to build and use but after adding up cost for the best built unit it may be cheaper to install an NVG241OR or an Atlas or STaK purpose-built unit.
The NVG241OR Rock-Trac transfer...
The NVG241OR Rock-Trac transfer case is the crme de la crme of modern Jeep transfer cases. With a 4.0:1 low gear ratio and short rear output it is a major factor that aids the Jeep Wrangler JK's off-road capability.
NVG241OR Rock-Trac
Usage: Jeep Wrangler TJ (1997-2006) and JK Rubicon (2007-present).
Notes: Offers 4.0:1 low gear ratio and a fixed yoke rear output. Aluminum case with built-in strengthening ribs in the rear half of case to withstand increased torque of low gears. It is chain-driven and uses a 23-spline input gear.
Weaknesses: Not many. This 'case is purpose-built for increased strength and ability.
Strengths: Many. This is an awesome T-case for all Jeep applications.
NP205
Usage: Many GM, Ford, Dodge, and International full-size truck applications from late 1960s through 1993.
Notes: Heavy duty gear-driven unit with cast iron case. Used circular six- and eight-bolt mounting bolt patterns and also a circle-eight or "racetrack", eight-bolt mounting pattern depending on year and vehicle model. Both drivers- and passenger-side front drop configurations. Used both male and female inputs with various shaft spline counts depending on year. 1.98:1 low gear ratio
Weaknesses: Low gear ratio is lacking, heavy unit for smaller rigs.
Strengths: Very heavy-duty. Excellent for heavy 4x4s with V-8 powertrain.