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How To Install Replace Rear Axle Differential Pinion Seal 84-91 GMC Jimmy SUV

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  1. step : Remove bolts from drive shaft (1:10)
    • Leave vehicle in gear to make it easier to remove the four bolts using your 7/16 wrench.
  2. step : Mark driveshaft (1:58)
    • Use a screwdriver to scuff the drive shaft and collar to use as a point of reference when reassembling later.
  3. step : Pull out drive shaft (2:15)
    • Using a larger screwdriver or pry bar, pull the drive shaft out.
    • Use a catch pan to collect any wayward transmission fluid.
  4. step : Clean and mark pinion seal (2:43)
    • Clean the pinion and surrounding area with a wire brush.
    • Set the parking brake on your vehicle.
    • Make a small mark on the pinion and bolt to line them up again later.
  5. step : Remove bolt from pinion (4:00)
    • Remove the bolt and pull off the collar using the 32mm or 1 and 1/8th socket wrench.
  6. step : Remove and replace seal (4:18)
    • Remove your old seal and replace with your new 1A Auto rear axle differential pinion seal.
    • Carefully tap the seal in with a hammer evenly until it is in place.
  7. step : Reassemble (5:30)
    • Using your line up marks, reassemble the yoke.
  8. step : Finish up (7:20)
    • Add gear oil to the transmission and put the drive shaft back in.
    • Add a little transmission fluid to help slide the drive shaft back in.
    • Put the yokes back on and tighten the four bolts to 20 foot pounds.

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Hi, I'm Mike Green. I'm one of the owners of 1A Auto. I want to help you save time and money repairing and maintaining your vehicle. I'm going to use my 20 plus years' experience restoring and repairing cars and trucks like this to show you the correct way to install parts from The right parts installed correctly, that's going to save you time and money. Thank you, and enjoy the video.

In this video, I'm going to show you how to replace the rear pinion seal on this 1986 GMC Jimmy, same as a whole bunch of different rear wheel drive vehicles, although the tools and bolt sizes may differ a little bit. The tools you'll need for this truck are a 7/16ths wrench, a hammer and cold chisel, 32 millimeter or 1 and 1/8th socket and ratchet, a flat blade screwdriver. Again, for your application, your sizes and things may differ a little bit.

On these GM vehicles, most of these bolts are 7/16ths. Actually, I have the truck in neutral, which is a little bit of a mistake. It's a lot easier if you leave it in gear, but if you're quick with your wrench, you can generally get them loose. The only thing is, if I twist the track drive shaft, and then give a pull on the wrench, it will move all four of these. The best thing is, you leave these on just a little bit, because you want to try and put the yokes in the same place. I'm just going to use a screwdriver and scratch in here a bunch, and scratch on here a little bit. Okay, that just lets me know that this side of the drive shaft goes into this side of the rear end. Now, you want a larger screwdriver or a pry bar, and your drive shaft comes out. Okay, and there's the front of the drive shaft. You can see, I've got a catch pan underneath. You want to make sure you do that, because on some transmissions, when you pull the drive shaft out, you'll lose fluid.

On the pinion seal here, the first thing I'm going to do is just take a wire brush and clean all of this stuff up. I'm going to get all of this caked-on dirt out of here. Now, you want to set the parking brake on your vehicle, so after this, the rear end is less likely to move. What I'm going to do is I'm going to make a mark right here in the pinion, okay? Then, I'm going to make another mark right here in the bolt. Okay, I can see down below that, there's one, two and then the third thread is inside. Basically, I know when I put this back together, I need to line up my marks and have two full threads showing, and the third is on the inside. Okay, so I made a nice mark there, and I made a mark in my bolt. I'm actually going to mark the bottom of my yoke here, too.

On this truck, 32 millimeters is fitting on there pretty well. It may be 1 1/8th inch. Now, this actually just pulls right off. Here's the seal that we're going to replace. Just take it from the side and rip right through it if you want to. Basically, just bend it up and pull it out. The old one comes right out. To put the new seal in, you just want to evenly make sure it goes in relatively easily here. I do have a specialized tool, once you have it in a certain amount. Just tap it in there just like that. Now, we still have this pointing down. My collar is kind of worn, so I'm not sure this is actually going to fix my issue, but on this vehicle, it's a truck with 190,000 miles on it. It's my winter truck, so I'm not too worried about it. I'm going to put it on.

This does get good contact with the seal there, so I've got my lineup mark there and my lineup mark there. I'll put my washer back in. My yoke's back on. Here's my pinion lineup, and then here's the lineup I put into there. I've got my washer in, and now I'm going to put my bolt on. Hopefully, you can see right here. That's my other lineup mark. This goes almost all the way. I'm actually going to use my impact wrench and put it on, probably another two turns or so. Okay, now I can see one. I'm starting to see one, so I need another turn at least. I can see one, and I'm starting to see two. I can actually see my mark over here. It's about a little less than of a turn. Now it's getting tight enough to where it's starting to move the wheels.

I've got my nut on there, and tightened up. You can see, here is one lineup. Here's the other lineup. I actually did get the bolt maybe 1/32 of a turn a little tighter, just because there was some play in here. It didn't really do anything. That's all lined up.

What I'm going to do now is put some fluid in the transmission. Basically, I'm going to take this plug out and just fill it up with gear oil until it comes out. Then, I'll put the drive shaft back on, and we're all set. I've got it all refilled. You want to wipe down the bottom of your rear end really well, that way you can check down here and make sure your time was well spent, and your rear differential's not leaking anymore.

Now, I'm going to speed through putting the drive shaft back in. I throw a little bit of transmission fluid on the front, and then it slips over the transmission. You might have to use a little hammer or rubber mallet to get it in. Once it gets past a certain point, it goes right in. Then, put the yokes back on. Tighten up those bolts to 20 foot pounds, and then make sure you lower the car. Put some transmission fluid back in it. Get the transmission fluid to the correct level, and you should be all set to go.

We hope this helps you out. Brought to you by, your source for quality replacement parts and the best service on the internet. Please feel free to call us Toll-Free 888-844-3393. We're the company that's here for you on the internet and in person.

Tools needed for replacement:

    General Tools

  • Chisel
  • Hammer

  • Ratchets & Related

  • Ratchet

  • Screwdrivers & Related

  • Flat Blade Screwdriver
  • Pry Bar

  • Sockets - Metric

  • 32mm Socket

  • Wrenches - SAE

  • 7/16 Inch Wrench

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