The transfer case is the most important part of the four-wheel-drive system in your rig. Typically, this means that you want something that gives outstanding work and exceptional reliability. But despite the array of transfer cases available, there is one question that needs to be answered. Who has proven himself to be tough and durable?
The four Wheeler got around to the old all-actually square discussion and made a list of our current favorites to answer this question. Surprisingly, there is not much discussion as we all chose basically the same units. In this list which is not in any specific order, you will find some familiar features which are proven performers in ‘Wheeling World.’ You’ll also see a few related tools in transfer-case technology and beef to a whole new level. One thing in common in all these transfer cases is that we will bolt any of them under our rig. In fact, some of us have.
The NP208 is an honest, lightweight, chain-driven transfer case. It is perfectly sufficient for everyday use, except perhaps the slip on the output shaft; there is nothing wrong with it naturally. It was used in various 1980s applications, including Jeep, General Motors, Dodge, and Ford pickups.
The primary concern of the NP208 is the output shaft slip yoke found on most applications. For everyday driving and the use of normal four-wheel drive, a slip yoke may not be an issue. For vehicles that are aggressive on off-road use, a high degree of flex or objective and lifted vehicles (especially with short wheelbases), a slip jock can quickly become the Achilles heel of a drive train system limiting its capacity. In addition to the concerns related to the driveshaft vibration, the slip yoke can easily get you stuck in the event of a U joint or driveshaft failure. In general, the vehicle can be hoisted at home by removing the rear driveshaft and relying only on the front axle. But after removing the driveshaft, the NP208 slip yoke will not fit, and the remanufactured transfer case will lose its full oil supply. Without lubrication, you are unlikely to make it away. Fortunately, there are upgrade kits on the market that will transform the transfer case into a fixed one and alleviate these worries.
Borg Warner manufactures the BW4404 chain. The BW4404 has an AWD torque-on-demand, part-time transfer case. This unit was used early in 1996. The BW4404 has a magnesium case and uses a greasy clutch system; this case was made with a left side drop output and had a low gear ratio of 2.72 to 1.
This unit may have issues with premature chain and sprocket cat and greasy coupler wear failure; mileage failure has also been observed in these parts. Another problem associated with the BW4404 transfer case is the failure of the input shaft. However, in general, the BW4404 design is perfect for the horsepower rating for which it is specified, receiving good ratings for operation in snow conditions.
The BW4405 transfer case is a Four Wheel Drive system. A common electronic module controls it. The transfer case can change the torque between the front and rear driveshafts to drive at full highway speed at 4WD when in automatic mode.
The BW4405 transfer case suffers from a mechanical failure that results in noise from the transfer case at the coast or during a downturn, or vice versa. Before this failure, the transfer case probably made a throbbing noise constant at 40-60 mph speed. On inspection, you will see the range hub and range fork damaged.
The BW4405 transfer case will sound if there is a difference in reading depth of more than 0.15 mm (0.06-in.) Between the front and rear wheels. The difference in the rolling portion can be caused by a difference in the tread of tire pressure. Remanufactured transfer cases can also make noise if the unit is low in fluid.
Dana 18 transfer case is a strong part of your vintage jeep that you can definitely trust. However, there will be a time when you have to change parts of your transfer case. You may have been few of the lucky ones to find this war-proven transfer case attached to a T86 transmission for sale. Even better if you have a strong T90 transmission for sale with a transfer case attached to it. The chances are that the Model 18 requires replacement parts in both situations.