How To Replace Pinion Seal GM 14 Bolt??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Dave1, Mar 16, 2003.

  1. Dave1

    Dave1 Registered Member

    Jan 4, 2002
    Likes Received:
    Winter Springs, (Central) Florida
    My truck is a 1986 GMC K25 3/4 ton heavy duty 4WD pick up with 4.10 gears, 350M, T400, NP208, 8600GVW, with factory stock rear end (what I believe is a GM Corp 14 bolt with 13" brakes).

    After a day in the woods/mud/and deep water of hog hunting with my Cur dogs (2 hogs caught) and during the truck wash down, I got a nose full of the dreaded smell of gear oil. A look underneath told the story as alot of gear oil is leaking out from the pinion seal and has been slung off the yoke all under the rear of the truck.

    My question is, how do I remove and replace the seal on this particular differential? Have heard on some differentials the yoke nut actually adjusts the pinion backlash. Is this one like that? (I had a shop replace another one one time and the differential whined from then on.) Is this an easy job I can do this myself or should I take it to a shop??

    Thanks for any advice/instructions, Dave
  2. Shaggy

    Shaggy 3/4 ton status

    Dec 15, 2000
    Likes Received:
    Los Banos, CA
    <font color="green"> The nut does not adjus the backlash, but it does adjust the pinion bearing preload. You can do it yourself, you just need to be careful about doing it correctly. The nice thing about the 14 bolt is that you can do the job on a bench since the pinion carrier is removable.

    Remove the pinion assembly and clamp it in a vice so you can get to the yoke and the seal. Mark the relationship between the pinion nut, pinion and the end of the pinion shaft, a scribe line should be fine. You want to be able to return these three items to the exact same positions after you replace the seal. Remove the nut, counting the number of turns so you make sure that you put it back on in the same place that it was. Replace the seal, then put the whole thing back together, lining up the three items mentioned above. The nut will likely take well over 150lbs of torque to get it back to where it was.

    When people mess these up it's because they don't return the pinion nut to where it was. If they overtighten it then the crush sleeve can get overcrushed, putting too much load on the pinion bearings. If it is not torqued enough then there isn't enough preload on the bearings, which can also cause them to burn up. Good luck!</font>

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