100K Mile Service GMC Sierra 1500 Truck 1999-2006 2nd Generation

Hey friends. It's Len here from 1A Auto. Today we have another 100K miles service. This is gonna be on a 2005 GMC Sierra with a 5.3 motor. Let's get into it.

Now, the first thing we're gonna talk about under the hood that's due every 100,000 miles is gonna be your spark plugs. The spark plugs on these particular engines is gonna be an iridium spark plug. Typically the iridium is gonna last a very long time, but it can eventually wear out. Generally, you want to go ahead and replace your iridium spark plugs every 100,000 miles.

Typically, when you replace the spark plugs, you wanna make sure that you replaced the wires at the same time because, of course, they're gonna be halfway removed at the time, and they might get damaged as well. Something I wanna mention about the iridium spark plugs real quick, is when you get them, you wanna make sure that the ground strap isn't bent over or pinned down near the electrode that you can see in there. If it is, you need to go ahead and replace that spark plug with a brand new one. You can't go ahead and use a gapper or anything like that because you could damage the extremely hard iridium on the spark plug. At which point, well, the spark plug's garbage anyway.

All right, now the second thing we wanna talk about on these trucks is the transmission fluid. This is typically gonna be due every 100,000 miles to be serviced. When you do it, you wanna make sure that you replace the pan gasket and the filter that's located in there as well. And when you replace the fluid, you wanna use Dexron-VI fluid. If you use the wrong fluid, you could potentially damage your transmission. Generally, there is two types of transmissions on these. One of them is gonna be considered an Allison Transmission, that one's gonna be more for like a heavy-duty type of instance. Generally, these trucks don't have the Allison Transmission, but if yours does, it's actually due every 50,000 miles. When it comes time to servicing it, though, you wanna obviously, like I said, drop the pan, replace the gasket and the filter. As you go to fill it, you're gonna fill it through the dipstick tube right here. Generally, start off with 5 quarts with Dexron-VI and then run it, get it up to operating temperature while you're on a nice level surface. Keep checking it to make sure you're within the hatch marks.

I'm gonna go ahead and pull this out. I'll wipe it off. Looking at the dipstick, you can see that there's multiple areas with a little bit of hatch marks on them. This area right up here is gonna be the hot line. So, after the vehicle has been running for a while and it's at operating temperature, you want the fluid to be right in between these lines. If it's up above it, well then, either you're not on a level surface, or you put in too much fluid. If you put in too much fluid, you need to make sure you get some out of there. You could potentially damage your transmission. Speaking of transmissions, if you happen to have a manual transmission in your truck, that fluid is actually due to be serviced every 150,000 miles. Obviously, that's a very extended period of service. Generally, at 100,000 miles it really couldn't hurt to go ahead and do it.

Now, another thing that's due at 150,000 miles is your engine coolant. Typically, that's a very long period of time for engine coolant. Generally, if you do it at 100,000 miles, you're gonna be much better off. This requires Dex-Cool Coolant and not the typical green. When you're servicing your coolant, you don't just drain and fill it. You wanna go ahead and flush out the existing coolant that's in there. That way there, it gets through the entire heater core and the engine block, and you're replacing it with brand new coolant. Any coolant that you do drain out of it and/or flush out of the system, you need to make sure that you recycle properly.

Now, 100K miles service is kinda like a milestone service. So we kinda went over everything that's actually due at 100,000 miles and even 150,000 miles, but I kinda like to check other things at 100,000 miles. Typically, something that people don't necessarily think about would be their brake fluid. On most vehicles you're gonna find that it requires DOT 3 brake fluid. DOT 3 brake fluid is hygroscopic fluid. Essentially what that means, it's gonna try to draw in any moisture that might be in the air. And, of course, if you were to look inside of here, if the seal isn't doing its job, it's going to collect a lot of gunk. If your brake fluid is contaminated in any way, well, you might have an issue with your braking system. It really couldn't hurt to go ahead and flush out that fluid.

And of course, there's a lot of other things under your hood that you're gonna wanna pay attention to. You're gonna have some other fluids such as maybe your washer fluid, your power steering fluid, or even your engine oil. You obviously wanna make sure that you're up to date on all of your maintenance on these things and, of course, to make sure that they're up to par. If your washer fluid is low, you try to use the squirters, you might not be able to see.

Other than that, you have your battery located right here. You wanna go ahead and make sure that you have at least 12 volts in your battery at all times, 12.4 would be preferable in all honesty. If you have a multimeter, you can easily test it by touching up against the positive and the ground here, and that of course is gonna let you know what's going on. Now, something that's a bonus that I just kinda wanna throw in here, since we're talking about the battery/the electrical system, you're gonna have your fuse box located right here. On these GMs, you're gonna have an issue that's pretty typical where mice make their way up inside here. And they make themselves a nice little home. As they're living in there, they tend to urinate or even make a mess. That can cause very bad electrical problems inside of your fuse box. So, you wanna make sure that this is clean and free of any debris.

A couple last things we wanna take a look at while we're under the hood would be, of course, checking that air filter. You want to check your serpentine belt, and tensioner and then, of course, check all of your coolant hoses. Make sure you don't see any leaks on those.

Now, the next thing that we're gonna wanna check is the front end on this. Obviously, we wanna take a look at the tires and make sure we have plenty of tread, but of course, if you can jack up the front end so that the front wheels are at least a little bit off the ground, you can grab onto it at 6 and 12 and give it a little shake up and down. If you feel any movement like this, it could generally be a wheel bearing, but overall, it usually comes down to either an upper ball joint or a lower ball joint. Grab your tire rod from side to side, give it a nice little shake like this. If you feel movement that way, generally it's an inner or an outer tie rod end.

Now, if you have an opportunity to be able to slide underneath your truck safely, you wanna, of course, take a look under here. You want to make sure you don't see any fluid leaks anywhere. If you do, you need to address them. Obviously, if you have a front, a transfer case, and a rear differential, you wanna check all those fluids as well. If it's time to service your front differential, you're gonna notice that there's a fill and a drain. The fill plug is right here, drain plug. The transfer case is also gonna have a fill and a drain. You have your fill, and your drain. And then for the rear differential, you really only have a fill on that and to drain it, you actually have to drop the pan cover that's on the backside there.

And I'd just kinda make this short and sweet at this point. You wanna continue on by checking other things such as maybe your brake lines, your fuel lines that run along the fuel rail here. If you see anything that looks like it's rotted and flaking, you obviously wanna try to replace that. It couldn't hurt to take a look at all your body mounts, make sure that they're in good condition. This one's very bad. You can check your driveshafts, make sure that all your U-joints are good. Typically, you can just give them a little shake. If it looks like they have a grease fitting, put a little grease in them. Other than that, take a look at your exhaust. Make sure you don't have any exhaust leaks. Obviously, that would be very bad, and just kinda take a quick peek at everything else, such as your leaf springs, your brakes while you're back here, and make sure that your brake cables work as they should.

Okay, friends. So that's pretty much what I've got for you for 100K miles service on an '05 GMC Sierra. There might be a couple of things I missed along the way. If you got something to say, leave it in the comments section below, because I always love to hear from you. If you liked the video, smash on that like button for me. It would mean the world. While you're at it, subscribe and ring the bell. That way there, you can be kept up with all of our latest content. Thanks.