Low RangeType/OutputDriveYearsApplicationAvail. Modifications
Dana 182.46:1gear/offsetpart‘45-71CJ,FC,PU,SW,C101Notes 1,2,3,4,5
Dana 202.03gear/centerpart‘63-79CJ,SJ,C101Notes 4,5,6,7
Dana 211.00gear/centerpart‘63-69SJN/A
Dana 2001.91gear/centerpart‘67-69M715N/A
Dana 3002.60gear/centerpart‘80-86CJNotes 8,10
BW-13392.57chain/offsetfull‘73-79SJNote 9
NP2312.72chain/offsetpart‘88-97TJ,YJ,XJNotes 12,13,14
NV2422.72chain/offsetpart/full‘87-97XJ,ZJNote 12
Atlas II3.77 or 4.33gear/centerpartAftermarket from Advance AdaptersNote 11

CJ=‘45-86 CJ-2A-CJ-8, YJ=‘87-96 Wrangler, TJ=‘97-up Wrangler, PU=‘47-65 Willys pickup, SW=‘49-65 Willys Station Wagon, SJ=Wagoneer, Grand Wagoneer, J-Series pickup, C-101=‘67-73 Jeepster Commando & C-104 Commando, XJ=‘84-up Cherokee, ZJ=‘93-98 Grand Cherokee, WJ=‘99-up Grand Cherokee

Note 1 Note 2 Note 3

Note 1: Advance Adapters Saturn overdrive. This unit fits on the Model 18 ‘45-71 transfer case, though Advance Adapters is working on a version to fit the WWII military transfer cases. It‘s a 25 percent overdrive (0.75 ratio), meaning it drops rpm by 25 percent. It‘s capable of handling up to 300 lb-ft of torque, according to the manufacturer.

Note 2: TeraLow builds a replacement gear set for the Model 18 with a 3.15:1 low range. The conversion works only on a ‘66-and-later Model 18 cases, ‘63-79 Wagoneer cases, or ‘72-9 Model 20 cases. The Model 20 case can be used with the offset output of the Model 18.

Note 3: O‘Brien‘s 4-Wheel West makes four replacement gear sets called the JP Rock Eaters for the Model 18 in 3.0:1, 3.6:1 4.10:1 and 4.86:1. The 4.10 and 4.86 kits require significant case modifications. The detailed instructions outline the necessary mods to be performed by competent machinists and certified welders, but O‘Brien‘s can supply modified cases or complete kits.

Note 4 Note 5 Note 6

Note 4: Hicks 4x4 Specialists offers a kit to drop the Model 20 low ranger from 2.03:1 to 2.46:1. Installation involves only very minor clearance grinding of the case and parts that are stronger than stock.

Note 5: O‘Brien‘s 4-Wheel West makes a tapered roller bearing kit to replace the roller bearings and thrust washers of the original setup. this is an option to the company‘s Model 18 and Model 20 Rock Eater kit, and it significantly quiets the Model 18 unit. O‘Brien claims a 300-325 percent over design compared to the stock setup.

Note 6: O‘Brien‘s 4-Wheel West offers two replacement gear sets for the Jeep Model 20 in 3.0 and 3.6:1 ratios. No welding is required, and only minor mods are necessary to the case and shift rail.

Note 7 Note 8 Note 9

Note 7: TeraLow offers a 3.15:1 low-range gear set for the Jeep model 20 in a kit that contains everything needed to do the swap. It requires only minor clearance grinding of the case for the larger gears.

Note 8: TeraLow‘s Dana 300 kit offers a whopping 4.0:1 low-range option. These quality gears are said to be very quite. Normally, clearance grinding isn‘t necessary for installation, but a tiny bit of grinding in one strategic spot will make assembly easier.

Note 9: MileMarker‘s part-time conversion for the BW-1339 Quadra-Trac eliminates the fuel-sapping full-time system, annoying clutch chatter, and need for special oil. It includes a new chain and locking front hubs.

Note 10 Note 11 Note 12

Note 10: Currie Enterprises Twin-Stick shifter for the Dana 300 evolved as an answer to automatic lockers up front. It allows the front axle to be uncoupled from the transfer case while in low-range. This is easier than climbing out and unlocking a hub to make a tight turn or shifting out of 4WD and low range at the same time.

Note 11: The Atlas II transfer case is manufactured by Advance Adapters and can replace nearly any transfer case in nearly any Jeep. It‘s an aluminum cased, gear driven design that‘s based on the best features of the bulletproof NP205 and Dana 300 transfer cases. It‘s available with 3.77 or 4.33:1 low-range gearing.

Note 12: Short-tailshaft kits for NP231s, and NP242s have appeared from a variety of manufacturers to answer the needs of lifted rigs with drive shaft angle problems. They‘re all variations on the same theme: conversion of the sliding rear output shaft to a fixed yoke and the loss of about 4 inches of drive line length. In the case of the JB Conversions kit, the replacement rear-output shaft is at least 50 percent stronger than the stock one.

Note 13 Note 14

Note 13: TeraLow‘s 4:1 low range kit for the NP231 includes a new heavy-duty rear case as well as a six gear planetary gear set that offers a 4.0:1 low range gearing.

Note 14: If you combing an NP-231 and an automatic front locker, you may experience the need for a 2WD low position on the transfer case to make trail maneuvering easier. Both TeraLow and JB Conversions supply suck a kit to add and extra position to this popular New Process case. Shown are the TeraLow pieces.


The preceding data was taken from "Jeep Transfer Case Encyclopedia" an article found in the November 1999 issue of Jp Magazine.


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