GM Full-Size Trucks 1970-1979 Repair Guide

New Process Model 205 Transfer Case Overhaul

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See Figure 1



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Fig. Fig. 1: Exploded view of the New Process Model 205 transfer case

The New Process Model 205 transfer case is a two-speed gearbox mounted between the main transmission and the rear axle. The gearbox transmits power from the transmission and engine to the front and rear driving axles.

CASE DISASSEMBLY



  1. Clean the exterior of the case.
  2.  
  3. Remove the nuts from the universal joint flanges.
  4.  
  5. Remove the front output shaft rear bearing retainer, front bearing retainer and drive flange.
  6.  
  7. Tap the front output shaft assembly from the case with a soft hammer. Remove the sliding clutch, front output high gear, washer and bearing from the case.
  8.  
  9. Remove the rear output shaft housing attaching bolts and remove the housing, output shaft, bearing retainer and speedometer gear.
  10.  
  11. Slide the rear output shaft from the housing.
  12.  

Be careful not to lose the 15 needle bearings that will be loose when the rear output shaft is removed.

  1. Drive the two 1 / 4 in. shift rail pin access hole plugs into the transfer case with a punch and hammer.
  2.  
  3. Remove the two shift rail detent nuts and springs from the case. Use a magnet to remove the two detent balls.
  4.  
  5. Position both shift rails in neutral and remove the shift fork retaining roll pins with a long punch.
  6.  
  7. Remove the clevis pin from one shift rail and rail link.
  8.  
  9. Remove the range shift rail first, then the 4WD shift rail.
  10.  
  11. Remove the shift forks and and sliding clutch from the case. Remove the input shaft bearing retainer, bearing and shaft.
  12.  
  13. Remove the cup plugs and rail pins, if they were driven out, from the case.
  14.  
  15. Remove the locknut from the idler gear shaft.
  16.  
  17. Remove the idler gear shaft rear cover.
  18.  
  19. Remove the idler gear shaft, using a soft hammer and a drift.
  20.  
  21. Roll the idler gear assembly to the front output shaft hole and remove the assembly from the case.
  22.  

REAR OUTPUT SHAFT AND YOKE



  1. Loosen rear output shaft yoke nut.
  2.  
  3. Remove shaft housing bolts, then remove the housing and retainer assembly.
  4.  
  5. Remove retaining nut and yoke from the shaft, then remove the shaft assembly.
  6.  
  7. Remove and discard snapring.
  8.  
  9. Remove thrust washer and pin.
  10.  
  11. Remove tanged bronze washer. Remove gear needle bearings, spacer and second row of needle bearings.
  12.  
  13. Remove tanged bronze thrust washer.
  14.  
  15. Remove pilot rollers, retainer ring and washer.
  16.  
  17. Remove oil seal retainer, ball bearing, speedometer gear and spacer. Discard gaskets.
  18.  
  19. Press out bearing.
  20.  
  21. Remove oil seal from the retainer.
  22.  

FRONT OUTPUT SHAFT



  1. Remove lock nut, washer and yoke.
  2.  
  3. Remove attaching bolts and front bearing retainer.
  4.  
  5. Remove rear bearing retainer attaching bolts.
  6.  
  7. Tap output shaft with a soft-faced hammer and remove shaft, gear assembly and rear bearing retainer.
  8.  
  9. Remove sliding clutch, gear, washer and bearing from output high gear.
  10.  
  11. Remove sliding clutch from the high output gear; then remove gear, washer and bearing.
  12.  
  13. Remove gear retaining snap-ring from the shaft, using large snapring picks. Discard ring.
  14.  
  15. Remove thrust washer and pin.
  16.  
  17. Remove gear, needle bearings and spacer.
  18.  
  19. Replace rear bearing, if necessary.
  20.  


WARNING
Always replace the bearing and retainer as an assembly. Do not try to press a new bearing into an old retainer.

SHIFT RAILS AND FORKS



  1. Remove the two poppet nuts, springs, and using a magnet, the poppet balls.
  2.  
  3. Remove cup plugs on top of case, using a 1 / 4 in. punch.
  4.  
  5. Position both shift rails in neutral, then remove fork pins with a long handled screw extractor.
  6.  
  7. Remove clevis pins and shift rail link.
  8.  
  9. Lower shift rails; upper rail first and then lower.
  10.  
  11. Remove shift forks and sliding clutch.
  12.  
  13. Remove the front output high gear, washer and bearing. Remove the shift rail cup plugs.
  14.  

INPUT SHAFT



  1. Remove snapring in front of bearing. Tap shaft out rear of case and bearing out front of case, using a soft-faced hammer or mallet.
  2.  
  3. Tilt case up on power take-off and remove the two interlock pins from inside.
  4.  

IDLER GEAR



  1. Remove idler gear shaft nut.
  2.  
  3. Remove rear cover.
  4.  
  5. Tap out idler gear shaft, using a soft-faced hammer and a drift approximately the same diameter as the shaft.
  6.  
  7. Remove idler gear through the front output shaft hole.
  8.  
  9. Remove two bearing cups from the idler gear.
  10.  

CASE ASSEMBLY



  1. Assemble the idler shaft gears, bearings, spacer and shims, and bearings on a dummy shaft tool and install the assembly into the case through the front output shaft bore, large end first.
  2.  
  3. Install the idler shaft from the large bore side, using a soft hammer to drive it through the bearings, spacer, gears, and shims.
  4.  
  5. Install a washer and new locknut on the end of the idler shaft. Check to make sure the idler gear rotates freely. Tighten the locknut to 150 ft. lbs. (203 Nm).
  6.  
  7. Install the idler shaft cover with a new gasket so the flat side faces the rear bearing retainer of the front output shaft. Install and tighten the two retaining screws to the proper torque.
  8.  
  9. Install the interlock pins into the interlock bore through the front of the output shaft opening.
  10.  
  11. Start the 4WD shift rail into the front of the case, solid end of the rail first, with the detent notches facing up.
  12.  
  13. Position the shift fork onto the shift rail with the long end facing inward. Push the rail through the fork and into the Neutral position.
  14.  
  15. Position the input shaft and bearing in the case.
  16.  
  17. Start the range shift rail into the case from the front, with the detent notches facing up.
  18.  
  19. Position the sliding clutch to the shift fork. Place the sliding clutch on the input shaft and align the fork with the shift rail. Push the rail through the fork into the Neutral position.
  20.  
  21. Install the roll pins that lock the shift forks to the shift rails with a long punch.
  22.  
  23. Position the front wheel drive high gear and its thrust washer in the case. Position the sliding clutch in the shift fork. Shift the rail and fork into the front wheel drive (4WD-Hi) position, while at the same time, meshing the clutch with the mating teeth on the front wheel drive high gear.
  24.  
  25. Align the thrust washer, high gear and sliding clutch with the bearing bore in the case and insert the front output shaft and low gear into the high gear assembly.
  26.  
  27. Install a new seal in the front bearing retainer of the front output shaft, and install the bearing and retainer and new gasket in the case. Tighten the bearing retainer cap screws to the proper torque.
  28.  
  29. Lubricate the roller bearing in the front output shaft rear bearing retainer, which is the aluminum cover, and install it over the front output shaft and to the case. Install and tighten the retaining screws to the proper torque.
  30.  
  31. Move the range shift rail to the High position and install the rear output shaft and retainer assembly to the housing and input shaft. Use one or two new gaskets, as required, to adjust the clearance on the input shaft pilot. Install the rear output shaft housing retaining bolts and tighten them to 35 ft. lbs. (47 Nm).
  32.  
  33. Using a punch and sealing compound, install the shift rail pin access plugs.
  34.  
  35. Install the fill and drain plugs and the cross-link clevis pin.
  36.  

IDLER GEAR



  1. Press the two bearing cups in the idler gear.
  2.  
  3. Assemble the two bearing cones, spacer, shims and idler gear on a dummy shaft, with bore facing up. Check end-play.
  4.  
  5. Install idler gear assembly (with dummy shaft) into the case, large end first, through the front output shaft bore.
  6.  
  7. Install idler shaft from large bore side, driving it through with a soft-faced hammer or mallet.
  8.  
  9. Install washer and new locknut. Check for free rotation and measure end-play. End-play should be 0-0.002 in. Tighten the locknut to 150 ft. lbs. (203 Nm).
  10.  
  11. Install the idler shaft cover and a new gasket. Tighten the cover bolts to 20 ft. lbs. (27 Nm).
  12.  

Flat side of cover must be positioned towards front output shaft rear cover.

SHIFT RAILS AND FORKS



  1. Press the two rail seals into the case.
  2.  

Install seals with metal lip outward.

  1. Install interlock pins from inside case.
  2.  
  3. Insert slotted end of front output drive shift rail (with poppet notches up) into back of case.
  4.  
  5. While pushing rail through to neutral position, install shift fork (long end inward).
  6.  
  7. Install input shaft and bearing into case.
  8.  
  9. Install end of range rail (with poppet notches up) into front of case.
  10.  
  11. Install sliding clutch on fork, then place over input shaft in case.
  12.  
  13. Push range rail, while engaging sliding clutch and fork, through to neutral position.
  14.  
  15. Drive new lockpins into forks through holes at top of case.
  16.  

Tilt case on power take-off opening to install range rail lockpin.

FRONT OUTPUT SHAFT AND GEAR



  1. Install two rows of needle bearings in the front low output gear and retain with grease.
  2.  

Each row consists of 32 needle bearings and the two rows are separated by a spacer.

  1. Position front output shaft in a soft-jaw vise, with spline end down. Place front low gear over shaft with clutch gear facing down; then install thrust washer pin, thrust washer and new snapring.
  2.  

Position snapring gap opposite the thrust washer pin.

  1. Place front drive high gear and washer in case. Install sliding clutch in the shift fork, then put fork and rail into 4-High position, meshing front drive high gear and clutch teeth.
  2.  
  3. Align washer, high gear and sliding clutch and bearing bore. Insert front output shaft and low gear assembly through the high gear assembly.
  4.  
  5. Install front output bearing and retainer with a new seal in the case.
  6.  
  7. Clean and grease rollers in front output rear bearing retainer. Install on case with one gasket and bolts coated with sealant. Tighten the bolts to 35 ft. lbs. (47 Nm).
  8.  
  9. Install front output yoke, washer and locknut. Tighten the locknut to 150 ft. lbs. (203 Nm).
  10.  

REAR OUTPUT SHAFT



  1. Install two rows of needle bearings into the output low gear, retaining them with grease.
  2.  

Each row consists of 32 needle bearings and the two rows are separated by a spacer.

  1. Install thrust washer (with tang down in clutch gear groove) onto the rear output shaft.
  2.  
  3. Install output low gear onto shaft with clutch teeth facing downward.
  4.  
  5. Install thrust washer over gear with tab pointing up and away. Install washer pin.
  6.  
  7. Install large thrust washer over shaft and pin. Turn washer until tab fits into slot located approximately 90° away from pin.
  8.  
  9. Install snapring and measure shaft end-play. End-play should be 0.00-0.027 in.
  10.  
  11. Grease pilot bore and install needle bearings.
  12.  

There are 15 pilot needle bearings.

  1. Install thrust washer and new snapring in pilot bore.
  2.  
  3. Press new bearing into retainer housing.
  4.  
  5. Install housing on output shaft assembly.
  6.  
  7. Install spacer and speedometer gear. Install rear bearing.
  8.  
  9. Install rear bearing retainer seal.
  10.  
  11. Install bearing retainer assembly on housing, using one or two gaskets to achieve specified clearance. Tighten the attaching bolts to 35 ft. lbs. (47 Nm).
  12.  
  13. Install yoke, washer and locknut on output shaft.
  14.  
  15. Position range rail in high, then install output shaft and retainer assembly on case. Tighten the yoke nut to 150 ft. lbs. (203 Nm).
  16.  

CASE ASSEMBLY



  1. Install power take-off cover and gasket. Tighten the attaching bolts to 15 ft. lbs. (20 Nm).
  2.  
  3. Install cup plugs at rail pin holes.
  4.  

After installing, seal the cup plugs.

  1. Install drain and filler plugs. Tighten to 30 ft. lbs. (41 Nm).
  2.  
  3. Install shift rail cross link, clevis pins and lock pins.
  4.  

 
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