Beginning with the 1999 model year, Isuzu NPR, GMC Forward Tiltmaster, Chevrolet Forward, Nissan UD and Mitsubishi Fuso trucks no longer use the JR403E Electromatic transmission.
These trucks now are equipped with the Aisin Seiki 450-43LE transmission (see Figure 1), a Toyota-designed transmission that is almost identical to a 1993-94 Toyota Land Cruiser A442F transmission.
The 450-43LE is fully computer controlled, using five solenoids – two shift, one timing, one lockup and one pressure-control – for transmission operation, all controlled by a transmission-control module.
The transmission uses a three-element lockup-type converter, six friction elements, two one-way clutches and three planetary gearsets, as illustrated in the cutaway in Figure 2 and the clutch on/off chart in Figure 3.
Figure 4 shows the shift-solenoid firing order.
The truck will not move in any forward gear range; there is no problem with reverse.
The low sprag, shown in Figure 5, has failed. The sprag elements have flattened and the inner race, which is the front planet carrier, has been worn down to the point where it will not hold (see Figure 6).
The entire front planet carrier and sprag assembly will have to be replaced.
These and other parts for the 450-43LE are available from RC Truck Parts, 305-863-3933.
The truck barely moves or there is considerable noise coming from the torque-converter area. The transmission fluid, when checked, is very dark and has a foul odor. When the pan is dropped and inspected, it is loaded with metal.
The torque converter has catastrophically failed internally, resulting in the conditions described (see Figure 7).
Note: When the transmission fluid is in this condition, the torque converter almost certainly is damaged and the pump body and pump cover also are unusable (see Figure 8).
Replace the torque converter, make other necessary repairs and thoroughly flush the transmission cooling system.
Note: Observation of this condition has shown that the valve body is usually trash and cannot be successfully reconditioned. Figure 9 identifies the valve-body components.
The transmission is slipping badly in first, third and reverse gears. In some instances there may be difficulty in movement in either direction.
These complaints are due to the failure of the front (C1) clutch and the rear (C2) clutch, which also are known as the forward and direct clutches, respectively.
This, however, is not the root cause of the problem. The root cause is the sealing-ring area of the center support, which seals the rear clutch (see Figure 10), and the O/D housing (see Figure 11), which seals the front clutch.
The steel rings wear the aluminum ring lands of the center support and the O/D housing, resulting in the failure of the front and rear clutches and causing the complaints described.
Replacement of the center support and the O/D housing will be necessary.
Note: Never use Teflon® rings on either of these assemblies; it will destroy the ring lands in a relatively short time.
After overhaul the transmission has no reverse movement and no third gear.
In the upper valve body is the C2 (direct) clutch checkvalve assembly (see Figure 12). This checkvalve contains a checkball that, if left out, will cause this complaint.
This checkvalve assembly switches C2 clutch-application oil to the direct clutch between the D third-gear circuit and C2 clutch-application circuit in the reverse range.
Refer to the illustration in Figure 12 for the correct C2 clutch checkvalve. The checkball in the C2 clutch checkvalve assembly is 6.35mm (0.250 inch) should you need one.
Note: For checkball locations refer to figures 13 and 14.
September 2004 Issue
Volume 21, No. 9
- Aisin Seiki 450-43LE: Preliminary Information
- Aisin Seiki 450-43LE: No Forward Movement
- Aisin Seiki 450-43LE: Severe Torque-Converter Damage
- Aisin Seiki 450-43LE: Slipping or No First, Third and Reverse
- Aisin Seiki 450-43LE: No Third or Reverse