- In a GM 4L80-E/4L80-EHD with trouble code 68 in overdrive or trouble code 39 in Drive 3, the cause can be mechanical. The units also have new-design fourth- and overrun-clutch steel plates.
- The oil-pump driveshaft in Ford AXOD/AXODE may be the culprit in no movement in forward or Reverse, or no converter-clutch apply at any speed.
- We also have updated electrical diagnosis and cautions on 1991-1992 Ford AXODE.
- Chrysler 41TE has a change in the overdrive/underdrive reaction plate, as well as a change in the 2-4 low/reverse reaction plate.
- In a Honda M24A, no reverse after overhaul may be caused by the bore plug that retains the servo control valve having been installed backward.
- Valve-body screens for GM 4L30-E units now are available individually from Isuzu. We list the part numbers for those screens.
After rebuild, the vehicle displays a no-converter-clutch condition, stores trouble code 68 when driven in overdrive and stores trouble code 39 when driven in D3.
Many electrical and mechanical reasons can cause these codes to be stored. If all of the electrical reasons have been eliminated, the cause may be that the TCC enable valve in the pump-cover assembly is in backward.
Remove the pump assembly and install the TCC enable valve in the direction that is shown in Figure 1, and ensure free movement after installation.
Beginning at the start of production, all 1997-model THM 4L80-E transmissions were built with new-design steel plates for both the fourth clutch and the overrun clutch. The plates now include turbulator holes (See Figure 2).
The holes interrupt fluid surface pressure to improve efficiency.
- (1) Overrun Steel Plates – New design has seven holes (See Figure 2).
- (2) 4th-Clutch Steel Plates – New design has four holes (See Figure 2).
The new-design steel plates are not recommended for previous models because of calibration considerations and changes.
- Fourth-Clutch Steel Plates (With Holes). . . . . 24204283
- Overrun-Clutch Steel Plates (With Holes) . . . 24204287
Before and/or after rebuild, the vehicle exhibits one of the following:
- (1) No movement in forward or reverse.
- (2) No converter-clutch apply at any speed.
The cause may be one of the following:
- (1) The converter feed passage in the oil-pump driveshaft is blocked with debris or was not machined properly to allow converter feed oil to enter the converter.
- (2) The oil-pump driveshaft is leaking or was not machined properly, allowing the converter feed passage and converter release passage to be connected.
Check the oil-pump driveshaft, and clean or replace as necessary (See Figure 3).
We have seen some replacement shafts, both reman and new, that were leaking between the converter apply and release passages.
- Oil-Pump Driveshaft (AXOD/AXODE) . . . E6DZ-7B328-A
Wires for the electronic pressure-control solenoid are fed through pins 1 and 6 of the black/gray case connector, on top of the transaxle (See Figure 4). Ohmmeter across terminals 1 and 6 should read 2.5-6.5 ohms resistance.
Caution! Popped A Computer Lately?
Modulated Lock-Up Solenoid (MLUS):
Wires for the modulated lockup solenoid (MLUS) are fed through pins 4 and 5 of the gray case connector, on top of the transaxle (See Figure 4). Ohmmeter across terminals 4 and 5 should read 0.75-2.0 ohms resistance if you have MLUS. The modulated lockup solenoid (MLUS) is only on the 1991 Lincoln. Taurus/Sable for 1991 use the regular lockup solenoid (LUS) that is described below. All models for 1992 model year are MLUS.
Lockup Solenoid (LUS):
Wires for the lockup solenoid (LUS) are fed through pins 4 and 5 of the black case connector, on top of the transaxle (See Figure 4). Ohmmeter across terminals 4 and 5 should read 16-40 ohms resistance if you have LUS. The lockup solenoid (LUS) is only on the 1991 Taurus/Sable. Lincoln for 1991 uses the modulated lockup solenoid (MLUS) that is described above. All 1992 models use the MLUS.
Transaxle Oil Temperature Sensor (TOT)
Wires for the Transaxle Oil Temperature (TOT) sensor are fed through pins 2 and 3 of the black/gray case connector on top of the transaxle (See Figure 4). Ohmmeter across terminals 2 and 3 should read the approximate resistance listed in the chart at the top of the next column. Resistance should decrease if transaxle is heated and should increase if transaxle is allowed to cool. Oil pan that is warm to the touch is about 105°F-158°F.
Shift Solenoid 1:
Wires for shift solenoid 1 are fed through pins 5 and 6 of the white case connector, on the side of the transaxle (See Figure 4). Ohmmeter across terminals 5 and 6 should read 12-30 ohms resistance.
Shift Solenoid 2:
Wires for shift solenoid 2 are fed through pins 1 and 2 of the white case connector, on the side of the transaxle (See Figure 4). Ohmmeter across terminals 1 and 2 should read 12-30 ohms resistance.
Shift Solenoid 3:
Wires for shift solenoid 3 are fed through pins 3 and 4 of the white case connector, on the side of the transaxle (See Figure 4). Ohmmeter across terminals 3 and 4 should read 12-30 ohms resistance.
The turbine-speed sensor is on the channel plate next to the left-hand axle seal. With ohmmeter across the two terminals of the TSS, there should be 100-200 ohms resistance.
Manual Lever Position Sensor (MLPS):
The manual lever position sensor is checked across pins 2 and 3 of the sensor as shown in illustration below. With ohmmeter across pins 2 and 3, the resistance reading should correspond to the chart below.
Sometime in 1999, two of the previous overdrive/underdrive reaction-plate selectives became plate packages, including the overdrive/reverse reaction plate and a 0.075-in. overdrive/under-drive reaction-plate tapered snap ring as shown in Figure 5.
- Part No. 4723682 (0.253 in.-0.257 in. OD/UD thickness) . . . . . . . . . . . Now Part No. 05017179AA
- Part No. 4723683 (0.234 in.-0.238 in. OD/UD thickness) . . . . . . . . . . . Now Part No. 05017514AA
Note: These two selective OD/UD reaction plates are available only in this package that includes the tapered snap ring and OD/reverse reaction plate.
Sometime in 1999, four of the previous 2-4/low-reverse reaction-plate selectives were changed to accommodate a new tapered snap ring as shown in Figure 6.
For increased durability of the tapered snap ring.
- (1) The 2-4/low-reverse reaction plate was machined to accept a new tapered snap ring.
- (2) The tapered snap ring was made 0.010-in. thicker to avoid breakage.
The thicker tapered snap ring is included in the new 2-4/low-reverse reaction-plate package when the part number ends with AA.
- Part No. 4377149 (0.262-in. thickness) . . . . . . . Now Part No. 4897455AA
- Part No. 4377148 (0.252-in. thickness) . . . . . . . Now Part No. 4897454AA
- Part No. 4412268 (0.242-in. thickness) . . . . . . . Now Part No. 4897453AA
- Part No. 4412267 (0.232-in. thickness) . . . . . . . Now Part No. 4897452AA
After overhaul, vehicles equipped with M24A transaxles may exhibit a no-reverse condition.
The cause may be that the bore plug, which retains the servo control valve in its bore, was assembled backward, exhausting line pressure from the manual valve in reverse.
Locate the servo control valve, which is in the secondary valve body, and assemble the bore plug correctly as shown in Figure 7.
Valve-body screens previously were unavailable, so a complete valve body had to be bought from Isuzu.
Parts personnel were unable to find the part numbers for the screens.
Part numbers now are available from Isuzu to order the valve-body screens individually. See Figure 8 for the location of the force-motor screen and Figure 9 for the location of the PWM band-control-solenoid screen.
- Force-Motor Screen (Isuzu part number)………………….8-96041-009-0
- PWM Band-Control-Solenoid Screen (Isuzu part number) …….8-96041-012-0
March 2000 Issue
Volume 17, No. 3
- THM 4L80-E/4L80-EHD: Trouble Code 68 In Overdrive Trouble Code 39 In Drive 3 All Electrical OK
- Ford AXOD/AXODE: No Movement or No Converter Clutch
- Ford AXODE (1991-1992 Only): Electrical Diagnosis (Updated)
- Chrysler 41TE: Overdrive/Underdrive Reaction-Plate Change
- Chrysler 41TE: 2-4/Low-Reverse Reaction-Plate Change
- Honda M24A: No Reverse
- THM 4L30-E: Valve-Body Screens