Isuzu Cars and Trucks 1981-1991

Transaxle Overhaul

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DISASSEMBLY
  1. Remove the clutch release bearing assembly from the transaxle. Attach the transaxle assembly to a suitable transaxle holding fixture.
  2.  
  3. Remove the rear cover assembly from the transaxle case.
  4.  
  5. Remove the control box assembly from the transaxle case.
  6.  
  7. Using a suitable tool, shift transaxle into gear. Remove the 5th speed shaft and discard the retaining nuts from the input and output shaft and discard the retaining nuts. Shift transaxle back into neutral, aligning the detents of the shift rails.
  8.  
  9. Remove the detent spring retaining bolts for 1st/2nd, 3rd/4th and 5th speeds and remove the detent springs and detent balls. Remove the reverse detent spring retaining bolts, spring and detent ball. Remove switches for 1st/2nd and 3rd/4th gear switch hole, if so equipped with shift speed indicator light.
  10.  
  11. Place 5th speed synchronizer in neutral. Remove the roll pin at 5th gear shift fork and discard the roll pin. Remove 5th gear synchronizer hub, sleeve, roller bearing and gear with the shift fork as an assembly from the output shaft. Using a suitable gear puller, remove 5th speed gear from the input shaft.
  12.  
  13. Remove 7 bearing retainer screws with Torxand#x00AE; bit (No. 45) from the bearing retainer assembly.
  14.  
  15. Remove the bearing retainer and shims from the input and output shafts. Keep shims in order.
  16.  
  17. Remove the reverse idler retaining bolt used to retain the reverse idler shaft at the transaxle case.
  18.  
  19. Remove the collar and thrust washer from the output shaft using a suitable gear puller.
  20.  
  21. Remove the 14 bolts retaining the transaxle case and separate the transaxle from the clutch housing.
  22.  
  23. Lift the 5th gear shaft. With the detent aligned facing the same way, remove 5th and reverse shafts at the same time.
  24.  
  25. Remove the reverse idle gear and reverse idle shaft.
  26.  
  27. Using a punch and hammer, remove the roll pin from the 1st/2nd shift fork and discard the roll pin. Slide 1st/2nd shaft upward to clear housing and remove fork and shaft from case.
  28.  
  29. Remove the cotter pin and then remove the pin and reverse shift lever.
  30.  
  31. Remove the input and output shafts with 3rd/4th shift fork and shaft as an assembly.
  32.  
  33. Remove the differential case assembly.
  34.  
  35. Remove the reverse shaft bracket and take out 3 interlock pins.
  36.  
  37. Remove the rear bearing outer races (input and output) from the transaxle case.
  38.  
  39. Remove the outer races for the input shaft front bearing, output shaft front and differential side bearings. Use special tool J-26941 with J-33367 or equivalent for removing the input and output races in the housing and the differential race in the case. Use special tool J-26941 or equivalent with a slide hammer to remove the differential race in the housing.
  40.  
  41. Remove the input shaft seal from the housing. Remove the clutch shaft only if replacement of bushing, bearing or shaft is required.
  42.  
  43. Remove the outer clutch shaft seal and outer clutch shaft bushing using special tools J-37245 with J-36190 or equivalent. Drive the bushings towards the outside of clutch housing.
  44.  
  45. Remove the clutch shaft and inner clutch shaft seal.
  46.  
  47. Remove the inner clutch shaft needle bearing using special tool J-37158 or equivalent. Position the puller legs under bearing and thread rod down to expand legs. Hold rod while tightening nut to remove the bearing.
  48.  



Click image to see an enlarged view

Fig. Exploded view of the MR8 manual transaxle

Input Shaft
DISASSEMBLY
  1. Remove the front bearing using special tool J-22912-01 or equivalent (inverted when installed on the shaft) with a suitable press.
  2.  
  3. Pull off the rear bearing, 4th gear, 3rd/4th synchronizer assembly and 3rd gear as a unit, using special tool J-22912-01 or equivalent (inverted when installed on the shaft) and a suitable press.
  4.  
  5. Remove the remaining parts from the input shaft.
  6.  

INSPECTION
  1. Clean parts with solvent and air dry.
  2.  
  3. Inspect shaft, spline wear for cracks.
  4.  
  5. Inspect gear teeth for scuffed, nicked, burred or broken teeth.
  6.  
  7. Inspect bearings for roughness of rotation, burred or pitted condition.
  8.  
  9. Inspect bearing races for scoring, wear or overheating.
  10.  
  11. Inspect synchronizers for damage or wear.
  12.  
  13. Measure the clearance between synchronizer blocker ring and inserts. Replace components if 0.146 in. (3.7mm) or less clearance exist.
  14.  
  15. Measure the clearance between blocker ring and gear. Replace components if not within 0.031 in. (0.8mm). This specification is the wear limit.
  16.  
  17. When reassembling synchronizer assemblies, each insert spring should support all 3 keys and each opening portion of the insert spring should face the opposite direction from the other.
  18.  

ASSEMBLY

NOTE
Before assembling apply oil to the thrust surfaces on all gears and washers.

  1. Install needle bearing, 3rd gear and the blocker ring on the input shaft.
  2.  
  3. Match the inserts of the 3rd/4th sleeve and hub assembly with the grooves of the blocker ring and press the sleeve and hub assembly and collar using special tool J-33374 or equivalent and a suitable press. Before installing, apply oil to the collar and hub of the collar. Check to ensure the insert springs do not interfere with the hub after installation.
  4.  
  5. Install the blocker ring, needle bearing, 4th gear and thrust washer on the input shaft. When installing the thrust washer install with the recessed area facing 4th gear.
  6.  
  7. Install the front and rear bearings using special tool J-33374 or equivalent and a suitable press. Before installing, apply oil to the bearing inside and race surfaces.
  8.  

Output Shaft
DISASSEMBLY
  1. Remove the front bearing using special tool J-22227-A and special tool J-33369 or equivalent and a suitable press.
  2.  
  3. Remove the rear bearing and 3rd/4th gear at the same time using special tool J-22912-01 (inverted when installed on the shaft) and a suitable press.
  4.  
  5. Remove the needle bearing, collar, 2nd gear, 1st/2nd gear synchronizer assembly, 1st gear and key as a unit using a suitable press.
  6.  
  7. Remove the thrust bearing and washer from the output shaft.
  8.  

INSPECTION
  1. Clean parts with solvent and air dry.
  2.  
  3. Inspect shaft, spline wear for cracks.
  4.  
  5. Inspect gear teeth for scuffed, nicked, burred or broken teeth.
  6.  
  7. Inspect bearings for roughness of rotation, burred or pitted condition.
  8.  
  9. Inspect bearing races for scoring, wear or overheating.
  10.  
  11. Inspect synchronizers assembly for damage or wear.
  12.  
  13. Measure the clearance between synchronizer blocker ring and inserts. Replace components if 0.154 in. (4mm) or less clearance exist.
  14.  
  15. Measure the clearance between blocker ring and gear. Replace components if not with 0.031 in. (0.8mm). This specification is the wear limit.
  16.  
  17. Measure the clearance between blocker rings and synchronizing cones for 1st and 2nd gears by positioning 1st gear then 1st/2nd synchronizer assembly then 2nd gear in the correct position. Replace the 1st/2nd gear synchronizer components if the measurement exceeds 0.059 in. (1.5mm).
  18.  
  19. When reassembling synchronizer assemblies, each insert spring should support all 3 keys and each opening portion of the insert spring should face the opposite direction from the other.
  20.  

ASSEMBLY

NOTE
Before assembling, apply oil to the thrust surfaces on all gear. Apply oil to all the bearing inside and race surfaces.

  1. Install the thrust washer, thrust bearing, needle bearing, 1st gear, inner, outer ring and blocker ring for 1st gear on the output shaft.
  2.  
  3. Match the inserts of the sleeve and hub assembly with the grooves of the blocker ring and press the sleeve and hub assembly together with the collar using special tool J-8853-01, pilot tool J-33369 or equivalent and a suitable press. Before installing the sleeve and hub assembly, oil should be applied to the hub and collar inside surface. After installation, apply oil to the collar outside surface. Check to ensure that the insert springs do not interfere with the hub after installation.
  4.  


NOTE
Install the 1st/2nd gear synchronizer in the correct position.

  1. Install the blocker ring, outer and inner ring for 2nd gear, needle bearing, 2nd gear and then the key. Make sure the key is positioned properly in the key groove.
  2.  
  3. Apply oil to the 3rd/4th gear inner surface, match the key with the key groove and fit the key together with the rear bearing. using special tool J-33374 or equivalent and a suitable press, press bearing on the shaft.
  4.  
  5. Press the front bearing on the shaft using special tool J-33368 or equivalent and a suitable press.
  6.  

Differential
DISASSEMBLY
  1. Remove the side bearing using a suitable gear puller.
  2.  
  3. Remove the 10 retaining bolts and remove the ring gear. Discard the ring gear bolts.
  4.  
  5. Using a small tool, pry the speedometer drive gear and or rotor from the differential case. Do not reuse the speedometer drive gear and or rotor.
  6.  
  7. Using a punch, drive out the lock pin and pull out the cross pin.
  8.  
  9. Remove the pinion gears, thrust washers, side gears and thrust washers.
  10.  

INSPECTION
  1. Clean with solvent and air dry.
  2.  
  3. Inspect the housing bearing race bore for wear, scratches or grooves.
  4.  
  5. Inspect the housing bushings for scores, burrs, roundness or evidence of overheating.
  6.  
  7. Inspect housing for cracks, threaded openings for damaged threads, mounting faces for nicks, burrs or scratches.
  8.  
  9. Inspect gear teeth for scuffed, nicked, burred or broken teeth.
  10.  

ASSEMBLY

NOTE
Before assembling, apply oil to the bearing inner and outer race surfaces.

  1. Install the 2 side gears on the differential case together with the thrust washers. Next, position the 2 thrust washers with pinion gears opposite of each other and install them in their positions by turning the side gear.
  2.  
  3. Insert the cross pin and make sure the backlash is within the rated range 0.0012-0.0032 in. (0.03-0.08mm). If the backlash is outside the rated range, adjust it by installing different size thrust washers.
  4.  
  5. Install lock pin and cross pin.
  6.  
  7. Heat using a suitable tool (do not use hot water) a new speedometer drive gear or rotor to about 200and#x00B0;F (93and#x00B0;C) and then install it on the differential.
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  9. Heat using a suitable tool the rear gear to 122-212and#x00B0;F (50-100and#x00B0;C), then apply oil on the inside diameter of the ring gear then position the gear on the differential case. Apply a small amount of oil to the bottom side of the 10 new bolt heads only, then install bolts and tighten to 73-79 ft. lbs. in a diagonal sequence. Apply oil to the cross pin, differential gears, thrust portion, side gear shaft portion and side gear spline portion before installation.
  10.  
  11. Install the side bearing on the differential case using special tool J-22919 or equivalent and an arbor press.
  12.  

TRANSAXLE ASSEMBLY
  1. Install the new input shaft seal in housing using special tool J-26540 or equivalent.
  2.  
  3. Install the front outer bearing races for the input shaft, output shaft and differential into the clutch housing. Always apply oil to the bearing races before installation and use suitable tools.
  4.  
  5. Apply grease to the 3 interlock pins and install on the clutch housing.
  6.  
  7. Install the reverse shift bracket on the clutch housing. Use 3rd/4th shift shaft to align bracket to housing. Install retaining bolts and tighten to 13 ft. lbs. (17 Nm) make sure shaft operates smoothly after installation.
  8.  
  9. Install the differential assembly, then install the input, output shaft with the 3rd/4th shift fork and shaft together as an assembly into the clutch housing. Make sure the lock pin is in the 3rd/4th shifter shaft before installing. The 3rd/4th shift shaft is installed into the raised collar of reverse shift lever bracket.
  10.  
  11. Install the 1st/2nd gear shift fork onto the synchronizer sleeve and insert the shift shaft into the reverse shift lever bracket. Align hole in fork with the shaft and install a new double roll pin.
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  13. Install the reverse lever on shift bracket.
  14.  
  15. Install the reverse and 5th gear shifter shaft and at the same time, engage reverse shaft with reverse shift lever. Make sure lock pin is in the 5th gear shifter shaft before installing.
  16.  
  17. Install the reverse idle shaft with the gear into the clutch housing. Make sure reverse lever is engaged in collar of gear.
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  19. Measure and determine correct shim size using special tool J-33373. To determine correct shim size follow assembly procedure Steps 11-17.
  20.  
  21. Position the outer bearing races on the input, output and differential bearings. Position the shim selection gauges on the bearings races in the correct position.
  22.  


NOTE
The 3 gauges are marked as input, output and differential.

  1. Position 7 spacers provided with special tool J-33373 evenly around the perimeter of the clutch housing.
  2.  
  3. Install the bearing and shim retainer on transaxle case. Torque retaining screws to 13 ft. lbs. (17 Nm). After final torque on screws, stake screws to the retaining plate.
  4.  
  5. Carefully position the transaxle case over the gauges and on the spacer. Install the 7 bolts alternately until case is seated on spacers. Install the 7 bolts alternately until case is seated on spacers. Tighten bolts to 10 ft. lbs. (13 Nm).
  6.  
  7. Rotate each gauge to seat the bearings. Rotate the differential case through 3 revolutions in each direction.
  8.  
  9. With the 3 gauges compressed, measure the gap between the outer sleeve and base pad using available shim sizes in preload shim sizes chart. The input shaft shim should be 2 sizes smaller than the largest shim that will fit in the gap. The differential should use a shim 3 sizes larger than that which will smoothly fit in the gap. The output shaft should use the largest shim that can be placed into the gap and drawn through without binding.
  10.  
  11. When each of the 3 correct shims have been selected, remove the transaxle case, 7 spacers and 3 gauges.
  12.  
  13. Position the shim selected for the input, output and differential into the bearing race bores in the transaxle case.
  14.  
  15. Install the rear input and output shaft bearing races using suitable tools.
  16.  
  17. Install the rear differential case bearing race using special tools J-8611-01 with J-8092 or equivalent and a press. Apply oil to the bearing race before installation. Press the bearing until seated in its bore.
  18.  
  19. Position the magnet in clutch housing. Clean the clutch housing and transaxle case mating surface, then apply a 1 / 8 in. (3mm) bead of Loctite No. 518 sealer or equivalent to the mating surfaces.
  20.  
  21. Install the transaxle case on the clutch housing. Install the reverse idle shaft bolt into the transaxle case. Tighten the retaining bolt to 28 ft. lbs. (38 Nm).
  22.  
  23. Install the 14 case bolts. Torque bolts to 28 ft. lbs. (38 Nm) in a diagonal sequence.
  24.  
  25. Install the drive axle seals using suitable tools.
  26.  
  27. Install the thrust washer and collar to the output shaft using special tool J-33374. Before installing, apply oil to the thrust surfaces and collar.
  28.  
  29. Install 5th gear to the input shaft. Install the needle bearing, 5th gear, blocker ring, hub/sleeve assembly with shift fork in its groove and back plate on the output shaft. Align shift fork on shift shaft and install a new double roll pin. Before installing apply oil to the output gear thrust surfaces.
  30.  
  31. Install the detent balls and detent springs for the reverse, 1st/2nd, 3rd/4th and 5th speeds. Install the retaining bolts and tighten to 18 ft. lbs. (25 Nm).
  32.  
  33. Install the 1st/2nd gear switch. Install the short pin and then the long pin into the 3rd/4th gear hole. Install 3rd/4th gear switch, if vehicle is equipped with a shift speed indicator light.
  34.  
  35. Apply Loctite No 262 sealer or equivalent to the threads of the input and output shafts. Install new retaining nuts and torque to 94 ft. lbs. (128 Nm). Stake nuts after reaching final torque.
  36.  
  37. Install a new gasket with the control box assembly on the transaxle case and torque the 4 bolts to 13 ft. lbs. (17 Nm). Stake the retaining nuts after final torque is applied and make sure transaxle shifts properly before installing the rear cover.
  38.  
  39. Install a new gasket with the rear cover. Install the retaining bolts and torque to 13 ft. lbs. (17 Nm).
  40.  
  41. If the clutch shaft, bushing, bearing and seals have been removed, installed new bearing into the clutch housing using special tools J-37159 with J-36190 or equivalent. Install new oil seal and clutch shaft. Install new outer bushing using special tool J-36037 or equivalent. Drive bushing inward until line on tool is flush with housing. Before installing, apply grease to both the inside and outside of bushing and bearing.
  42.  
  43. Install the clutch release bearing.
  44.  
  45. Measure the rotating torque on the input shaft. When measuring, the input shaft should be to the upper side and the differential assembly to the lower side. The rotating torque specification should be less than 7 inch lbs.
  46.  

 
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