Our faithful GMC Envoy has just turned 150k and it was time to do the 50k maintenance on her again. For this maintenance routine, I added cleaning the throttle body to it since it seems to be a problem area for these vehicles and I’d rather do it at a set interval than have the Check Engine Light come on and annoy my wife!
First up, and possibly the hardest of the maintenance items, is replacing the transmission filter and fluid that comes out with it. I would flush the entire system, but I don’t have the machine to do it. There are a couple of articles on the internet that show how to get this done, but I’d rather not run the transmission fluid pump without fluid in it. So I just replace the fluid that gets removed when I drop the pan, it is about half the total capacity of the system. My fluid was still red when I checked it so I did not think this was a problem, and it is how I did it before. You will need to get a transmission filter kit that comes with the filter and the gasket to complete this job. Be careful when purchasing the filter kit, some kits are for a shallow pan (Mine was for a shallow pan) and some are not. The difference is the shape of the pan and whether or not there is a lip on the side.
The first thing that you need to do is put a tarp down on your driveway! This will keep all that transmission fluid on the tarp and not on your driveway. This is a messy job, so take preparations. If you’re skinny, you may be able to crawl underneath the car to gain access to the transmission pan bolts, but I am not so I needed to put the car up on jack stands. Safety first!
Put a tarp down! It’s already on jack stands!
Then you can loosen the 16 13mm bolts that hold the transmission pan to the transmission. What I try to do is to loosen the bolts at the back of the pan first to let the fluid drip, then run out in a semi controlled state. Like I said, this is messy but I like to contain as much of the fluid as possible. When the fluid starts to come out you can position your catch can where it will do the most good and keep as much of the fluid in the pan as possible. Once you have completed this disaster, you can remove the pan completely.
You can see the bolts on the sides of the pan.
Transmission Fluid will start to leak out…
Once the pan is removed, you can pour the rest of the fluid that was in the pan into your catch can. You did do this carefully right? The pan is full of fluid so loosen the bolts in a way where you are able to lower the pan straight down and spill as little fluid as possible. Once you have this done, you will want to clean the inside of the pan. Pay special attention to the magnet and get this as clean as you can to remove all the debris that has been attracted to it. You don’t want to put that garbage back into the system now that you have gotten it out.
The pan is resting next to the catch can, I spilled about a quart of fluid on the tarp.
Clean the pan and the magnet. The donut is the magnet.
Now, replace the filter. It is the black cartridge that is in the picture below. Just wiggle it a little bit and pull it down. This should not be that difficult. There is also a washer that comes with the new filter, if you feel like trying to replace it, go ahead. I find that it is more trouble than it is worth. My existing washer looked fine so I did not pull it out. Put the new filter in, just put the stem part in the hole and push up till it is secure.
The black box is the transmission filter
The hole is where the stem on the filter gets installed.
Set the gasket on your freshly cleaned transmission pan. I used 4 bolts to hold it in place. You can then slide it in place and start the bolts to hold the pan up. Then you can put the rest of the bolts in place. Tighten the pan up. I’m sure that there’s a torque spec to the bolts but I just tightened them up keeping in mind that I did not want to crush and damage the gasket. Don’t get me wrong, they are tight but no overly so.
New gasket on pan.
Now, you will need to fill the transmission fluid back up. I put in 3 quarts of Dexron VI right away to get some on the stick, and be satisfied that I would not do any damage. I then started the car and let it run a little bit. This got the pump to work and I added another 1 ¾ quart to the system. Once this level no longer dropped, I took the truck for a ride and made sure everything was working properly.
The next step in the 50k maintenance is to replace the transfer case fluid. You will need to purchase Auto Trak 2 transfer case fluid at a GM dealer. 2 quarts should be sufficient. This is very similar to replacing the fluid in a manual transmission, remove the lower drain plug, it is a giant Allen bolt. Let the fluid drain out. Replace the plug and remove the fill plug, also a giant Allen bolt. Put the fluid back in. The only difference is that you will need some kind of fluid pump to get the new fluid back into the transfer case. Fill the case with fluid until it starts to leak out of the fill hole. This is a little less than 2 quarts.
This is the lower plug
This is the fill plug.
Giant Allen key to get it out!
Fluid Pump to get the Auto Trak 2 in.
The last thing that I did for the 50k maintenance was clean the throttle body. I needed to remove the plastic “Vortec” plenum to gain access to the 4 10mm bolts that hold the throttle body in place. You will also need to remove the fuel return line and the TPS sensor connector from the throttle body to completely remove it.
You will need to remove the plenum. There are two 10mm bolts that hold it on on the exhaust side.
Remove the 4 bolts
The TPS sensor connection
And the fuel return line. Push down on that little tab to slide it off.
Remove the throttle body from the truck and use throttle body cleaner to clean the throttle body to spic and span condition. You should be able to move the butterfly by hand to get to all the carbon build up that is on the unit. Clean it all off and re-install the unit.
Dirty Throttle Body. Not really that dirty, i cleaned it not too long ago.
Clean throttle body.
There is one other thing that I usually do at 50k intervals, a coolant system flush and fill. I did not do it this time because I just replaced the thermostat not that long ago so that coolant is fresh. This will wait till 200k, if the truck makes it that far!