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GM Astro/Safari 1985-1996 Repair Guide

Pinion Flange Seal



See Figures 1, 2 and 3

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Fig. Fig. 1: Measure the pinion flange pre-load (force necessary to turn the flange) before loosening the retaining nut

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Fig. Fig. 2: A companion flange holder tool is necessary to loosen or tighten the nut

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Fig. Fig. 3: Use the proper sized seal installation tool or driver to install the replacement pinion seal

Because the pinion shaft flange is installed and tightened to achieve a set-preload, the current preload must be measured and matched during installation. The BEST way to achieve this is with a beam type inch lbs. torque wrench with a needle pointer.

In order to perform this procedure you will need a companion flange holding tool and a seal installer.

  1. Raise and support the rear of the vehicle safely using jackstands. If possible, lift and support the front of the vehicle as well to keep fluid from draining through the front of the axle housing (when the pinion flange and seal are removed). If this cannot be done, you should remove the rear axle cover in order to drain the fluid.
  3. Remove the rear wheels and drums to remove all load from the pinion shaft, except the required pre-load
  5. Matchmark and remove the driveshaft from the vehicle. If desired, the driveshaft can be left attached to the transmission (or transfer case, as applicable), but if so, it must be wired up to the body to prevent damage to the slip yoke U-joints. Also, it must be wired out of the way since you'll be working at the pinion flange.
  7. Using an inch lbs. torque wrench, measure the force necessary to turn the pinion. This measurement equals the combined pinion bearing, seal, carrier bearing, axle bearing and seal pre-load. IT MUST BE MATCHED UPON INSTALLATION SO MEASURE CAREFULLY.
  9. Make accurate matchmarks among the pinion stem, pinion flange and pinion flange nut. Also, count the number of exposed threads on the pinion stem for reference. Again, this will be used to help assure that the proper pre-load is achieved upon installation.
  11. Secure the pinion flange using a companion flange holding tool such as J 8614-01, then loosen the flange nut.
  13. Remove the pinion flange nut and washer.

If the front of the vehicle is not supported significantly higher than the rear and you have not drained the rear axle, have a drain pan handy to catch any leaking fluid.

  1. Remove the pinion flange. The holding tool can provide a useful hand-hold.
  3. Remove the old seal using a seal removal tool, but BE CAREFUL not to score or damage the sealing surface in the rear axle housing bore.
  5. Check the sealing surface of the pinion flange for tool marks, nicks or damage such as a groove worn by the seal. Replace the flange if necessary. Check the axle housing bore for burrs that might cause leaks around the outside of a new seal.

To install:
  1. Install the new seal using J 23911, or an equivalent seal driver/installation tool.
  3. Coat the outside of the pinion flange and the inside of the sealing lip (on the new seal) with GM seal lubricant No. 1050169, or equivalent.
  5. CAREFULLY install the pinion flange to the shaft.

DO NOT attempt to hammer the flange onto the shaft stem. Damage could occur and the pre-load measurements could be rendered useless.

  1. Install the washer and retaining nut, then tighten the nut as-close-as possible to the reference mark (with the same number of exposed shaft threads as noted during removal) WITHOUT going past the mark. Turn the nut a little at a time, turning the pinion flange several times after each tightening to set the rollers.

If the companion flange holder is used while tightening the nut, make sure it is removed before each pre-load measurement.

  1. Using an inch lbs. torque wrench, measure the pre-load (amount of effort necessary to turn the pinion) achieved by this setting. Continue to tighten the nut a little at a time, stopping to measure the pre-load again, until the pre-load measured during removal is matched.

If the original pre-load measurement was below 3 inch lbs. (0.34 Nm), then set the pre-load to 3-5 inch lbs. (0.34-0.56 Nm) during installation.

  1. Align and install the driveshaft.
  3. Install the brake drums, followed by the tire and wheel assemblies.
  5. Remove the jackstands and carefully lower the vehicle.