JEEP T-CASE SPECS AND MODIFICATIONS
| Model |
Low Range |
Type/Output |
Drive |
Years |
Application |
Avail. Modifications |
| Dana 18 |
2.46:1 |
gear/offset |
part |
‘45-71 |
CJ,FC,PU,SW,C101 |
Notes 1,2,3,4,5 |
| Dana 20 |
2.03 |
gear/center |
part |
‘63-79 |
CJ,SJ,C101 |
Notes 4,5,6,7 |
| Dana 21 |
1.00 |
gear/center |
part |
‘63-69 |
SJ |
N/A |
| Dana 200 |
1.91 |
gear/center |
part |
‘67-69 |
M715 |
N/A |
| Dana 300 |
2.60 |
gear/center |
part |
‘80-86 |
CJ |
Notes 8,10 |
| BW-1339 |
2.57 |
chain/offset |
full |
‘73-79 |
SJ |
Note 9 |
| NP219 |
2.60 |
chain/offset |
full |
‘80-82 |
SJ |
N/A |
| NP208 |
2.61 |
chain/offset |
part |
‘80-91 |
SJ |
N/A |
| NP229 |
2.61 |
chain/offset |
part/full |
‘83-86 |
SJ |
N/A |
| NP228 |
2.61 |
chain/offset |
full |
‘85-91 |
SJ |
N/A |
| NP207 |
2.72 |
chain/offset |
part |
‘84-87 |
YJ,XJ |
N/A |
| NP231 |
2.72 |
chain/offset |
part |
‘88-97 |
TJ,YJ,XJ |
Notes 12,13,14 |
| NV242 |
2.72 |
chain/offset |
part/full |
‘87-97 |
XJ,ZJ |
Note 12 |
| NV249 |
2.72 |
chain/offset |
full |
‘96-97 |
ZJ |
N/A |
| NV247 |
2.72 |
chain/offset |
full |
‘99 |
WJ |
N/A |
| Atlas II |
3.77 or 4.33 |
gear/center |
part |
Aftermarket from Advance Adapters |
Note 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: 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: 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: 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: 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: 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 from "Jeep Transfer Case Encyclopedia" an
article found in the November 1999 issue of Jp Magazine.
|
| |
|
Onboard
Air
