NP208F (E4TA-7A195-GA) Powerflow
TSB 92-01-08 FOUR WHEEL DRIVE (4X4) - GENERAL INFORMATION, OPERATING CHARACTERISTICS AND SERVICE TIPS
Published: 01/06/92
LIGHT TRUCK: 1990 and prior BRONCO II
1992 and prior AEROSTAR, BRONCO, F-150, F-250, F-350, RANGER
1991-92 EXPLORER
ISSUE: Ford 4-wheel drive vehicles were discussed at length in the 1991 April, May and June issues of Shop Tips. Topics included locking hubs, transfer cases, vehicle operating characteristics, driveline windup and service tips. This information is being reprinted here to better assist the technician with questions concerning 4WD operation and service.
ACTION: Refer to the following pages for Ford 4WD information.
In the 1980 model year, Ford introduced chain type transfer cases. Chain drives provide significant advantages (Figure 1). Most noticeable of all, the transfer case is easier to shift. Equally important, in 2-wheel drive, all the 4-wheel drive components are disengaged, reducing noise and component wear and maintaining fuel economy. This is accomplished by placing the high and low range planetary gears ahead of, and separate from, the drive shifting mechanisms. When the 4-wheel drive locking collar and the front locking hubs are disengaged, the whole front-wheel drive system is isolated and does not affect 2-wheel drive operation. Incorporated in chain-driven transfer cases is a positive pressure oil pump driven by the output shaft to the rear wheels. This provides lubrication to the transfer case whenever the rear drive shaft is turning - either during vehicle operation or when the vehicle is towed.
NOTE: IT IS IMPORTANT TO CONSULT THE VEHICLE'S OWNER GUIDE BEFORE TOWING ANY 4 x 4. THERE ARE SPEED AND DISTANCE RESTRICTIONS THAT VARY FROM VEHICLE TO VEHICLE.
Chain drive transfer cases may be manually or electrically shifted; for example, the New Process Model 208. Although not currently used in production, the operating principles are the same as Warner 1354 and 1356 models. This lightweight, chain-driven transfer case was introduced in 1980 for use in Bronco, F-150, F-250 and F-350 4x4s. It was in continuous use until the 1987 model year and is a typical example of how chain drive works. Speed selection is controlled by a single lever shift mechanism that provides a choice of Neutral, 2-High, 4-High and 4-Low.
The top center diagram shows the planetary gear set in cross section. At the center, attached to the input shaft, is the sun gear. This gear meshes with four gears that surround it like planets (which is why this component is called a planetary gear). In turn, the four gears mesh with an outer gear called the annulus. Annulus is another word for ring. As the sun gear turns, the four planetary gears attempt to rotate. If the annulus ring gear is locked (as it is in low gear), the planetary gears "walk" around the inside of the annulus. If the planetary gears are locked to their gear cage (as in high gear), the whole planetary assembly (planetary gears, planetary cage and annulus) rotate as a single unit.
When the driver selects 2H, the hub of the planetary gear assembly slides rearward, putting the transfer case into the high speed range (direct drive). The input shaft and the rear output shaft are locked together (Location # 1, upper left diagram). This results in direct drive, straight through to the rear drive shaft. The whole planetary gear set rotates, forcing the output shaft to turn at the same speed as the input shaft. In addition, the 4-wheel drive locking collar is disengaged so none of the 4WD components turn.
In 4-wheel drive high range (4H), the planetary gear set stays where it was in 2H. The action of the shift lever causes the 4-wheel drive clutch to move forward, locking the chain sprocket to the rear output shaft (Location # 2, upper right diagram). Now, both the rear and the front wheels are being driven in the high range.
To get maximum pulling power, the driver selects 4L. When this happens, the planetary gear set moves forward, and the annulus gear engages a locking plate (Location # 3, lower left diagram). With the annulus unable to turn, the planetary gears "walk" around the inside. The result is that the planetary gear cage now turns more slowly than the input shaft. Because the planetary cage is attached directly to the output shaft, the output shaft now rotates at a slower speed than the input shaft. This action increases the pulling power available to the wheels. It's like having an additional set of lower gears for extra power.
The bottom right diagram shows the power flow condition with the shift selector in neutral. No power is transmitted to either front or rear in this position. All the planetary gears turn freely with the input shaft, and the chain sprocket floats freely on highly efficient needle bearings.
RECENT TRANSFER CASE DEVELOPMENTS
During the 1980's, Ford introduced other transfer cases that eventually replaced the New Process 208; the Borg-Warner 13-56, which is used on Bronco and F-Series and comes in two versions: Mechanical shift and the electrically controlled "Touch Drive" (a.k.a. Electronic Shift-on-the-Fly ESOF) in which the shifts are activated electrically (not mechanically). The basic functions of this system are much the same as any other 4x4 transfer case. By touching the control switch on the instrument panel, the driver can select either 2- or 4-wheel high plus 4-wheel low range, but not Neutral.
NOTE: IT IS IMPORTANT TO REMEMBER THAT ELECTRICALLY SHIFTING TRANSFER CASES DO NOT HAVE A SELECTABLE NEUTRAL POSITION. BECAUSE OF THIS, IF VEHICLES EQUIPPED WITH ELECTRIC SHIFT ARE TO BE TOWED FOR LONG DISTANCES, THE REAR DRIVE SHAFT SHOULD BE DISCONNECTED. IF THIS IS NOT DONE, THE TRANSFER CASE (WHICH IS PROTECTED BY POSITIVE LUBRICATION) WILL DRIVE THE TRANSMISSION (WHICH IS NOT WELL LUBRICATED UNDER THESE CONDITIONS), AND THE TRANSMISSION MAY "BURN UP."
__________________________________________
TSB 83-03-24 TRANSFER CASE - NP208 - RANGE FORK AND NYLON ANNULUS HUB WEAR
LIGHT TRUCKS 1982-83 BRONCO, F150-250 (4x4)
New Process Gear Model 208 Transfer Cases on the above vehicles built after January 19, 1982 have a new range fork and annulus gear assembly design.
The annulus gear hub and web assembly (7B066) can be damaged when the transfer case is operated with low lube fluid levels or with a rough surface finish fork or thrust washer. This will result in transfer case shifting difficulties. The damaged nylon hub will appear to be melted or severely scored and must be replaced. The range fork (7289) and thrust washer (7D484) must also be replaced since surface finish damage or sharp edges created during the prior condition can cause accelerated wear of the new hub and web assembly and result in a repeat service. The transfer case should be refilled with 7 pints of new automatic transmission fluid lube (XT-2-QDX) and checked for any leaks. With the vehicle in a level position, the lube fluid must be up to fill plug opening.
PART NUMBER . . . . . PART NAME . . . . . . . . . . . . . . CLASS
E2TZ-7B066-A . . . . . . Hub and Web . . . . . . . . . . . . . . . B
E1TZ-7289-B . . . . . . . Range Fork . . . . . . . . . . . . . . . . C
E1TZ-7D484-A . . . . . . Thrust Washer . . . . . . . . . . . . . . BM
XT-2-QDX . . . . . . . . . . Transmission Fluid-Dexron II . . V
____________________________________________
That TSB disagrees with this chart on the fluid capacity:
![np208f.jpg NP208F (E4TA-7A195-GA) Powerflow
TSB 92-01-08 FOUR WHEEL DRIVE (4X4) - GENERAL INFORMATION, OPERATING CHARACTERISTICS AND SERVICE TIPS
Published: 01/06/92
LIGHT TRUCK: 1990 and prior BRONCO II
1992 and prior AEROSTAR, BRONCO, F-150, F-250, F-350, RANGER
1991-92 EXPLORER
ISSUE: Ford 4-wheel drive vehicles were discussed at length in the 1991 April, May and June issues of Shop Tips. Topics included locking hubs, transfer cases, vehicle operating characteristics, driveline windup and service tips. This information is being reprinted here to better assist the technician with questions concerning 4WD operation and service.
ACTION: Refer to the following pages for Ford 4WD information.
In the 1980 model year, Ford introduced chain type transfer cases. Chain drives provide significant advantages (Figure 1). Most noticeable of all, the transfer case is easier to shift. Equally important, in 2-wheel drive, all the 4-wheel drive components are disengaged, reducing noise and component wear and maintaining fuel economy. This is accomplished by placing the high and low range planetary gears ahead of, and separate from, the drive shifting mechanisms. When the 4-wheel drive locking collar and the front locking hubs are disengaged, the whole front-wheel drive system is isolated and does not affect 2-wheel drive operation. Incorporated in chain-driven transfer cases is a positive pressure oil pump driven by the output shaft to the rear wheels. This provides lubrication to the transfer case whenever the rear drive shaft is turning - either during vehicle operation or when the vehicle is towed.
NOTE: IT IS IMPORTANT TO CONSULT THE VEHICLE'S OWNER GUIDE BEFORE TOWING ANY 4 x 4. THERE ARE SPEED AND DISTANCE RESTRICTIONS THAT VARY FROM VEHICLE TO VEHICLE.
Chain drive transfer cases may be manually or electrically shifted; for example, the New Process Model 208. Although not currently used in production, the operating principles are the same as Warner 1354 and 1356 models. This lightweight, chain-driven transfer case was introduced in 1980 for use in Bronco, F-150, F-250 and F-350 4x4s. It was in continuous use until the 1987 model year and is a typical example of how chain drive works. Speed selection is controlled by a single lever shift mechanism that provides a choice of Neutral, 2-High, 4-High and 4-Low.
The top center diagram shows the planetary gear set in cross section. At the center, attached to the input shaft, is the sun gear. This gear meshes with four gears that surround it like planets (which is why this component is called a planetary gear). In turn, the four gears mesh with an outer gear called the annulus. Annulus is another word for ring. As the sun gear turns, the four planetary gears attempt to rotate. If the annulus ring gear is locked (as it is in low gear), the planetary gears "walk" around the inside of the annulus. If the planetary gears are locked to their gear cage (as in high gear), the whole planetary assembly (planetary gears, planetary cage and annulus) rotate as a single unit.
When the driver selects 2H, the hub of the planetary gear assembly slides rearward, putting the transfer case into the high speed range (direct drive). The input shaft and the rear output shaft are locked together (Location # 1, upper left diagram). This results in direct drive, straight through to the rear drive shaft. The whole planetary gear set rotates, forcing the output shaft to turn at the same speed as the input shaft. In addition, the 4-wheel drive locking collar is disengaged so none of the 4WD components turn.
In 4-wheel drive high range (4H), the planetary gear set stays where it was in 2H. The action of the shift lever causes the 4-wheel drive clutch to move forward, locking the chain sprocket to the rear output shaft (Location # 2, upper right diagram). Now, both the rear and the front wheels are being driven in the high range.
To get maximum pulling power, the driver selects 4L. When this happens, the planetary gear set moves forward, and the annulus gear engages a locking plate (Location # 3, lower left diagram). With the annulus unable to turn, the planetary gears "walk" around the inside. The result is that the planetary gear cage now turns more slowly than the input shaft. Because the planetary cage is attached directly to the output shaft, the output shaft now rotates at a slower speed than the input shaft. This action increases the pulling power available to the wheels. It's like having an additional set of lower gears for extra power.
The bottom right diagram shows the power flow condition with the shift selector in neutral. No power is transmitted to either front or rear in this position. All the planetary gears turn freely with the input shaft, and the chain sprocket floats freely on highly efficient needle bearings.
RECENT TRANSFER CASE DEVELOPMENTS
During the 1980's, Ford introduced other transfer cases that eventually replaced the New Process 208; the Borg-Warner 13-56, which is used on Bronco and F-Series and comes in two versions: Mechanical shift and the electrically controlled "Touch Drive" (a.k.a. Electronic Shift-on-the-Fly ESOF) in which the shifts are activated electrically (not mechanically). The basic functions of this system are much the same as any other 4x4 transfer case. By touching the control switch on the instrument panel, the driver can select either 2- or 4-wheel high plus 4-wheel low range, but not Neutral.
NOTE: IT IS IMPORTANT TO REMEMBER THAT ELECTRICALLY SHIFTING TRANSFER CASES DO NOT HAVE A SELECTABLE NEUTRAL POSITION. BECAUSE OF THIS, IF VEHICLES EQUIPPED WITH ELECTRIC SHIFT ARE TO BE TOWED FOR LONG DISTANCES, THE REAR DRIVE SHAFT SHOULD BE DISCONNECTED. IF THIS IS NOT DONE, THE TRANSFER CASE (WHICH IS PROTECTED BY POSITIVE LUBRICATION) WILL DRIVE THE TRANSMISSION (WHICH IS NOT WELL LUBRICATED UNDER THESE CONDITIONS), AND THE TRANSMISSION MAY "BURN UP."
__________________________________________
TSB 83-03-24 TRANSFER CASE - NP208 - RANGE FORK AND NYLON ANNULUS HUB WEAR
LIGHT TRUCKS 1982-83 BRONCO, F150-250 (4x4)
New Process Gear Model 208 Transfer Cases on the above vehicles built after January 19, 1982 have a new range fork and annulus gear assembly design.
The annulus gear hub and web assembly (7B066) can be damaged when the transfer case is operated with low lube fluid levels or with a rough surface finish fork or thrust washer. This will result in transfer case shifting difficulties. The damaged nylon hub will appear to be melted or severely scored and must be replaced. The range fork (7289) and thrust washer (7D484) must also be replaced since surface finish damage or sharp edges created during the prior condition can cause accelerated wear of the new hub and web assembly and result in a repeat service. The transfer case should be refilled with 7 pints of new automatic transmission fluid lube (XT-2-QDX) and checked for any leaks. With the vehicle in a level position, the lube fluid must be up to fill plug opening.
PART NUMBER . . . . . PART NAME . . . . . . . . . . . . . . CLASS
E2TZ-7B066-A . . . . . . Hub and Web . . . . . . . . . . . . . . . B
E1TZ-7289-B . . . . . . . Range Fork . . . . . . . . . . . . . . . . C
E1TZ-7D484-A . . . . . . Thrust Washer . . . . . . . . . . . . . . BM
XT-2-QDX . . . . . . . . . . Transmission Fluid-Dexron II . . V
____________________________________________
That TSB disagrees with this chart on the fluid capacity:
[url=https://www.supermotors.net/registry/media/831131][img]https://www.supermotors.net/getfile/831131/thumbnail/towaxletrans86.jpg[/img][/url]](https://www.supermotors.net/getfile/818969/fullsize/np208f.jpg)