How to Replace Alternator 73-82 GMC Jimmy Full Size

Brought to you by 1AAuto.com, your source for quality replacement parts and the best service on the Internet.

Hi, I'm Mike Green. I'm one of the owners of 1A Auto. I want to help you save time and money repairing or 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 1AAuto.com. The right parts installed correctly: that's going to save you time and money. Thank you and enjoy the video.

In this video, we're going to show you alternator replacement on this 1986 GMC Jimmy, really the same as many cars from the '50s through the '80s. Usually, the tools you'll need are just various wrenches from 7/16 to 9/16 or 10 millimeters to 15 millimeters and what wrenches you'll need will vary by vehicle.

One of the first things you want to do, is disconnect your negative battery cable. Here, you can see the alternator down in here. What we're going to first want to do, is remove our air cleaner. That gives us a little bit of room. In this vehicle, these AC lines are kind in our way. This is a half-inch bolt here. Now, we're going to disconnect this connector here which has just got a little thumb tab and then it pulls out.

On the back of the alternator here is a little boot and that's a 10 millimeter or probably a 7/16 inch nut. We're going to remove that and unplug that wire. On this truck, it is a 10 millimeter nut. It loosens up pretty easy and disconnects. Now, we're going to loosen this bolt and this bolt. After we loosen them, then we'll take the belt, we'll loosen the belt, take it off and we'll pull the bolts up the rest of the way and take the alternator out. On this truck, this lower bolt is a 9/16 inch. For this upper bolt, a half inch wrench is working. As you can see now, the alternator moves. I'm going to remove the belt. I will take the alternator all the way up. It's easier to get the bolt done. I have a bolt on the back of the alternator or nut that helps on these trucks to -- a lot of times what happens is this bolt is you put it in and it will strip so if you put a bolt on the back of it, it helps to hold it that much better. I'm just going to use my air ratchet to get this bolt down here. I'm going to lift up on the alternator as I pull this long bolt out. I'm going to rotate it out. I'll take it up and out.

Here's our new alternator from 1A Auto. Here's the original one from the truck. Like I said, the original one has a bracket back here. There's nothing wrong with this one on the truck. I'm just doing it as an example. I'm going to put the old one back in because like I said there's nothing wrong with it but you would just swap that bracket onto here. Then you could see other differences. This happens a lot. You might need to change the pulley over because you can see this has a multi groove pulley. If you need to change a pulley over, this is a 5/16 inch shaft. I've got a T50 Torx bit or 5/16 and you just put it in there and then this is a 15/16 nut. You can get that off, loosen that bolt up, take off the pulley and swap your pulley. That's if your application needs it. In a lot of cases, you have the single groove anyway. Here's another thing you need to look for. As I look on this one, here's the bottom of it, then here's a bottom of the new alternator so they're lined up. It's the clock position of the post. On the new one, my post is here which is basically the same clock position as my original. This one's not a problem but sometimes you could have it to be 90 degrees off or maybe even 180 degrees off. If this is the case, you can change the clock position. Actually, there's another video and that shows you how to do it on this type of alternator.

Now, you've swapped pulleys, if necessary, and changed the clock position if you had to. Basically, put the alternator back in opposite of how it came out. Put it down in, make sure all your wires are back and visible and see you don't pinch anything in between. Get it roughly into place. Let's take our long bolt. I just kind of shook it around a little bit so I can get that bolt to move through. Put it on the back side, here, where it needs to be. Then for the top bolt, we'll use the air ratchet to get this bolt in. Not tight yet, just in further. Get this top bolt a little closer to where it should be. Again, on that top bolt, I have a nut on the back side. Get it on. Now we can plug this back in. Reconnect our battery wire. You want to make sure you put this boot back on because if that battery wire touches any metal, it will spark and weld itself. Now, for the belt, make sure it's down around the crank. Get it up on the alternator. In order to tighten the belt, you're probably going to want a nice big bar like this but you can also probably use a large screwdriver. You want to pull that alternator out. There's a hole right here that I have my bar into and then I can pry up and out. Hopefully you can pry out on the alternator. I can pry on the alternator to tighten up the belt. I'll pry up on the alternator here, get the belt tight. You only want to feel . maybe be able to kind of flip it a quarter of an inch. I will tighten it at the top. As I pull it out, now we're going to tighten up this top bolt. Now we tighten the bottom one. Now, what we can do at this point is before we put the air cleaner and everything else back together, we're going to reconnect the negative battery cable, tighten it up. There's our voltage guaage. I should be able to start it up and the alternator shouldn't squeak and then that gauge should go up to 13 volts. Everything looks well. Now, we can bolt this back on. Depending on your vehicle, just do what you need to do to get everything back together.

We hope this video helps you out. Brought to you by www.1AAuto.com, 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.