Isuzu Cars and Trucks 1981-1991

5-Speed Overhaul Early 4-Wheel Drive P'up and Trooper

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BEFORE DISASSEMBLY

Cleanliness is an important factor in the overhaul of the Isuzu 5 speed transmission. Before opening up this unit, the entire outside of the transmission assembly should be cleaned, preferably with a high pressure washer such as a car wash spray unit. Dirt entering the transmission internal parts will negate all the time and effort spent on the overhaul. During inspection and reassembly all parts should be thoroughly cleaned with solvent then dried with compressed air.

Wheel bearing grease, used to hold thrust washers and lube parts, should not be used. Lube seals with clean SAE 30 weight engine oil and use ordinary unmedicated petroleum jelly to hold the thrust washers, needle bearings and to ease the assembly of seals, since it will not leave a harmful residue as grease often will.

Before installing bolts into aluminum parts, always dip the threads into clean transmission fluid. Anti-seize compound can also be used to prevent bolts from galling the aluminum and seizing. Always use a torque wrench to keep from stripping the threads. The internal snaprings should be expanded and the external rings should be compressed, if they are to be reused. This will help insure proper seating when installed.

TRANSMISSION DISASSEMBLY
  1. Remove the backup light switch, transfer case side assembly and shift block if not already done.
  2.  
  3. Remove the clutch release lever, front cover, Belleville spring and top shaft bearing snapring.
  4.  
  5. Remove the speedometer driven gear and transfer countershaft lock plate.
  6.  
  7. Remove the transfer housing bolts and pull the mainshaft, counter gear shaft and top gear shaft from the main housing. The intermediate plate and transfer housing will still be attached to the gear shafts.
  8.  



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Fig. Major component disassembly early 4WD P'up and Trooper

Mainshaft, Counter and Top Gear Shafts
DISASSEMBLY
  1. Remove the detent spring plate, springs and balls using a pencil magnet.
  2.  
  3. Hold a round bar against the ends of the shift rods to prevent damage. Remove the spring pins from the 1st/2nd, 3rd/4th and 5th/rev shift rods. Remove the rods and arms from the transmission.
  4.  
  5. Remove the interlock pin and plug.
  6.  
  7. Remove the input hub thrust nut using a wrench J29041 or equivalent. Remove the thrust input hub, input gear, needle bearings, collar and bearing snapring.
  8.  
  9. Remove the mainshaft bearings snapring, bearing, oil guide bolt and oil guide.
  10.  
  11. Remove the intermediate case from the shafts.
  12.  
  13. Remove the snapring, snapring thrust ring, retaining ring, 5th gear thrust ring and 5th gear washer.
  14.  
  15. Remove the counter gear locknut, washer and counter shaft end bearing. Use a 3 jaw puller to pull the 5th counter gear and bearing off the shaft.
  16.  
  17. Remove the 5th gear with the synchronizer cone, needle bearings and 5th blocker ring.
  18.  
  19. Engage the top/3rd synchronizer with the 3rd gear and the 1st/2nd side synchronizer with the 1st gear. Remove the mainshaft locknut and washer with the wrench J33441 or equivalent.
  20.  
  21. Remove the 5th/rev synchronizer assembly, reverse gear and needle bearings.
  22.  
  23. Remove the reverse idler shaft locknut, thrust washer, reverse idler gear and thrust washer.
  24.  
  25. Remove the intermediate plate from the shafts.
  26.  
  27. Remove the top shaft bearings snapring and top shaft with the synchronizer cone. Using a bench press, remove the top shaft bearing.
  28.  
  29. Remove the top shaft needle bearings and 3rd/4th blocker ring.
  30.  
  31. Remove the mainshaft snapring, 3rd/4th synchronizer assembly and 3rd/4th blocker ring.
  32.  
  33. Remove the 3rd gear assembly with the synchronizer cone and needle bearings.
  34.  
  35. Remove the gears and bearings from the mainshaft, using a bench press and bearing remover J2291201 or equivalent.
  36.  
  37. From the above assembly, remove the mainshaft bearing using a press. Remove the bearing collar, thrust washer, low gear assembly with the synchronizer cone, needle bearings, collar, 1st/2nd blocker ring, 1st/2nd synchronizer assembly, 1st/2nd blocker ring and 2nd gear assembly.
  38.  
  39. Remove the needle bearings from the 2nd gear.
  40.  
  41. Remove the reverse counter gear and bearing from the counter gear using a press. Remove the front counter shaft bearing snapring, front bearing, rear bearing snapring, conical spring and unbolt the reverse idler shaft.
  42.  



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Fig. Removing the countershaft lock plate and distance plate



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Fig. Mainshaft, cluster gear and top gear disassembly early 4WD P'up and Trooper



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Fig. Trust input hub nut



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Fig. Mainshaft nut



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Fig. Countergear and bearing removal

INSPECTION
  1. Using a micrometer, check the shift arm thickness where it rides on the synchronizer. 1st/2nd = 0.276 and 190.311 in. (7.0 and 197.9mm), 3rd/4th = 0.256 and 190.284 in. (6.5 and 197.2mm), transfer = 0.236 and 190.268 in. (6.0 and 196.8mm) and 5th/rev = 0.248 and 190.272 in. (6.3 and 196.9mm).
  2.  
  3. Using a inside slide ruler, check the free length of the detent springs. 1st/2nd, 3rd/4th and reverse = 0.985 and 191.091 in. (25.0 and 1927.7mm) and transfer = 1.615 and 191.694 in. (41.0 and 1943.0).
  4.  
  5. Using a spring tension tester, check the detent spring tension. 1st/2nd, 3rd/4th and reverse = 13.9 and 1914.7 lbs. (6.3 and 196.7 kg) and transfer = 19.8 and 1924.3 lbs. (9.0 and 1911 kg).
  6.  
  7. Using a feeler gauge, check the clearance between the blocker ring and gear. 1st/2nd = 0.032 and 190.067 in. (0.8 and 191.7mm), 3rd/5th = 0.032 and 190.059 in. (0.8 and 191.5mm) and top gear = 0.032 and 190.051 in. (0.8 and 191.3mm).
  8.  
  9. Using a feeler gauge, check the clearance between the blocker rings and inserts. Standard clearance 0.138 and 190.158 in. (3.51 and 194.00mm).
  10.  
  11. Using a feeler gauge, check the clearance between the clutch hub and inserts. Standard clearance 0.0004 and 190.012 in. (0.01 and 190.3mm).
  12.  
  13. Using a dial indicator and holding fixture, check the mainshaft run-out. Limit 0.001 in. (0.05mm).
  14.  
  15. Using an inside T-gauge, check the gear inside diameter. 1st/rev = 1.773 and 191.777 in. (45.0 and 1945.1mm), 2nd/3rd gear = 1.615 and 191.619 in. (41.0 and 1941.1mm), transfer idler = 1.300 and 191.304 in. (33.0 and 1933.1mm) and 5th = 1.261 and 191.264 in. (32.03 and 1932.10mm).
  16.  
  17. Using a micrometer, check the clearance between the bushing and idler gear shaft. Standard clearance 0.0016 and 190.0059 in. (0.041 and 190.150mm).
  18.  
  19. Using a dial indicator, check the spline play. Clutch hub 0.0 and 190.0079 in. (0.0 and 190.20mm) and reverse gear 0.0024 and 190.0078 in. (0.062 and 190.200mm).
  20.  
  21. Using a dial indicator, check the play in the ball bearings. Limit 0.068 in. (0.2mm).
  22.  
  23. Replace components that do not meet specifications.
  24.  



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Fig. Shift arm thickness check



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Fig. Detent spring check



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Fig. Blocker ring to gear clearance check 4-speed

ASSEMBLY
  1. Onto the mainshaft, install the 2nd gear needle bearings and 2nd gear with synchronizer cone. The taper cone on the gear must face rearward.
  2.  
  3. Install the 1st/2nd blocker ring and 1st/2nd synchronizer assembly. The parallel oil grooves in the clutch hub must be on the same side as the heavy chamfer on the sleeve. Make sure the inserts are fitted into the grooves in the blocker ring. Make sure the sleeve slides smoothly. Install the 1st/2nd blocker ring.
  4.  
  5. Install the needle bearing collar onto the shaft with a press and collar installer J33851.
  6.  
  7. Install the needle bearings, 1st gear with synchronizer assembly and the low thrust washer with the oil groove facing forward.
  8.  
  9. Install the mainshaft radial bearing with a press and bearing installer. Install the reverse thrust washer with the oil groove facing rearward.
  10.  
  11. Press on the reverse needle bearing collar. Install the needle bearings, 3rd gear with synchronizer cone and 3rd/4th blocker ring.
  12.  
  13. Install the 3rd/4th synchronizer assembly with the side of the hub with the higher boss facing the light chamfer of the sleeve. Install the mainshaft selective snapring after measuring the distance between the shaft and the 3rd/4th clutch hub.
  14.  
  15. Install the 3rd/4th blocker ring, needle bearings and top gear shaft bearing using a press. Install the bearing snapring.
  16.  
  17. Install the top shaft with synchronizer cone.
  18.  
  19. Install the front and rear counter shaft bearings using a press. Install the snaprings.
  20.  
  21. Install the counter gear shaft, reverse idler gear and reverse idler shaft. Torque the idler shaft retaining bolts to 16 ft. lbs. (22 Nm).
  22.  
  23. Install the mainshaft radial bearing snapring and counter gear bearing snapring into the intermediate plate. Use a holding fixture J29768 or equivalent to align the mainshaft and countershaft with the intermediate plate.
  24.  
  25. Install the reverse idler thrust washer, reverse idler gear with bushing, thrust washer and locknut. Torque the locknut to 87 ft. lbs. (120 Nm).
  26.  
  27. Install the needle bearings into the reverse gear and install the assembly onto the mainshaft.
  28.  
  29. Install the 5th/rev synchronizer assembly. The clutch hub with the higher boss must face the heavy chamfer of the sleeve.
  30.  
  31. Install the mainshaft lock washer and nut. Using the nut installer wrench J33441 or equivalent, torque to 101 ft. lbs. (140 Nm).
  32.  
  33. Install the 5th blocker ring, 5th gear with synchronizer cone, needle bearings and thrust washer. Install the thrust washer and lock ball onto the shaft using the snapring.
  34.  
  35. Install the thrust ring and thrust ring snapring so the opening in the snapring is positioned at a right angle to the opening in the thrust ring. Install the thrust ring retaining ring and bearing snapring.
  36.  
  37. Install the 5th counter gear, counter end bearing, plain washer and locknut. Torque the locknut to 101 ft. lbs. (140 Nm).
  38.  
  39. Install the adapter case, oil guide and oil guide bolt. Torque the book bolt to 15 ft. lbs. (20 Nm).
  40.  
  41. Install the mainshaft center bearing and snapring.
  42.  
  43. Install the mainshaft snapring, input gear thrust collar, needle bearings, input thrust gear, input thrust hub an input hub nut. Using a nut wrench J29041 or equivalent, torque the nut to 101 ft. lbs. (140 Nm).
  44.  
  45. Install the interlock pin and plug.
  46.  
  47. Install the 1st/2nd shift arm, 3rd/4th shift arm, 3rd/4th shift rod, 1st/2nd shift rod and spring pins.
  48.  
  49. Install the 5th/rev shift arm and shaft.
  50.  
  51. Install the detent balls, springs, plate and torque the retaining bolts to 16 ft. lbs. (22 Nm).
  52.  



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Fig. 2nd gear positioning



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Fig. Low/2nd synchronizer assembly



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Fig. Synchronizer assembly 1. key, 2. spring, 3. clutch



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Fig. Top/3rd synchronizer assembly



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Fig. Mainshaft, cluster gear and top gear assembly



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Fig. Low/rev trust washer oil groove position

 
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