[DeTomaso] Differential bearing replacement Info.

[charles buthala]

This post is for information only.
  I replaced the bearings in the ZF differential and wanted to share it with the forum.
  First off if you do this, measure the backlash and contact pattern prior to dissacembly, I failed to do this so I had no  baseline.  Many people on this forum helped me complete this job and I would not have tackled this job if it were not for this help.
  I purchased standard bearings from a local source matching the numbers etched in the races of each bearing.  From Production Tool supply I purchased a shim pack kit of .001 to .030 material to make the shims I needed.
  Additionally I purchased a 0 to 30 lb. fish weight scale that was accurate to +/- 0.1 lb to measure the torque (Traction Force) for the differential. 
   A special note is needed here, I did not disassociate the transmission gearing from the differential gear when measuring the differential traction force.  I measured the traction force of the pinion gear and calculated the associated torque (Force / Traction) imparted on the differential.  
  The ZF manual states a Traction force of 7.7 to 11 Lbf.  with the differential alone, with the transmission  as described above it liberates 3 Lbf  additional at the mid point of gear contact.  When measuring the tension of a string wrapped around the differential,, rotation-in the proper direction, the force should be between 12 & 16 lbf.
  EACH STEP MEASURE: FORCE, BACKLASH, GEAR CONTACT PATTERN BOTH DRIVE AND COAST SIDES.
  First Shim Pack was the original configuration.
  Measure the torque of Diff X.XX & bluing of gear contact pattern of both drive and cost side of ring gear. 
  Second Shim pack was  an estimate.
  Measure the torque of Diff Y.YY
  Third Shim Pack of Diff. Calculated using linear interpolation of Shim thickness vs. force. This will give you the proper shim pack for the preload on the bearings.  
  Now the shim packs must be moved from left to right in order to adjust the backlash / gear pattern between the pinion gear and the ring gear.
  Fourth shim Pack 
  Should be your verification of the proper shims.  reassembly will be required for completion.  This process is best completed without the output shaft and radial bearing installed until the last stage.  
  I created an EXE calculator for the interpolation, so if you are going to do this you are welcome to the file.
  A Few last notes.
  My ring gear and pinion had a Dead Zero marking on them, it looks like a Thata symbol.  Aligning the pinion and ring gear is a good idea. When I did this the contact pattern at proper backlash was improved.
  Backlash is etched in the ring gear as S.P. X.XX
  Hope this help others, this is my 2 cent.
   
   
   
   
   

 
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