Transmission oil, or fluid, as it's commonly known, is susceptible to breaking down just as engine oil. As such, the fluid needs changing at certain intervals. However, unlike engine oil, these intervals aren't nearly as frequent. Jeep recommends the transmission on the Grand Cherokee be serviced every 20,000 to 30,000 miles, depending on your operating conditions. While it's best to have it flushed, performing a drain and fill at home is better than simply ignoring it.
Before you begin to drain a single drop from your transmission, make sure you have the right fluid, transmission pan gasket and filter for your specific year, make and model.
Having the wrong filter will mean you won't be able to install it and, instead, will have to stop midservice and return to the store to buy the correct one.
Having the wrong fluid can mean far worse, up to and including ruining your transmission. Your Cherokee should take either ATF+3 or ATF+4 transmission fluid, but check with your vehicle's specific owner's manual to be sure. In a drain-and-fill procedure, you'll only be able to change four to six quarts, but it's best to have a case on hand.
It's also helpful to take a look at your transmission pan before heading to the store. You should note the specific shape of the pan and any numbers or letters embossed into it. This will allow you to be better educated when purchasing the pan gasket and filter, so you don't get home and find yourself holding a bag filled with wrong parts.
Take Your Time
Your transmission pan will have between 15 to 20 bolts holding it in place, depending on the specific transmission. Don't take them all out at once. Instead, loosen them all about 1/4-inch and then remove the bolts at one end to allow the fluid inside to drain into your drop pan. Otherwise, you may end up wearing transmission fluid, which comes with a lovely smell that might hang around for several days.
When you're taking the pan off, it may have a tendency to stick to the transmission, so carefully pry it down at the end where you removed the bolts. Be extremely cautious not to scratch the sealing surface or deform the pan.
Once you have the pan off, take a few minutes to get out from under the Jeep and clean the pan thoroughly. Get all the old gasket off the pan, clean all the old fluid out of it, then make sure it's totally clean before putting the new gasket on it. Some transmissions have a round magnet in the pan to catch all the tiny metal shavings that come with transmission wear. Clean that off as well before reinstalling the pan.
You'll also want to clean the sealing surface on the bottom of the transmission before putting the pan back on.