The young group is listening to "Sweet Home Alabama" by Lynyrd Skynyrd in the van at the beginning of the film. The film takes place between 18 and 20 August 1973. The song was not released until 1974, featured on the band's album, "Second Helping".
When the Sheriff is holding the drivers licenses of the three characters who are laying on the ground, what appears to be their date of birth is shown to be the same on all three, 3-11-92. Also, even though they are supposedly from three different states, the printing and information on the licenses are identical. They show the same address, "37218 N. A..." (you cannot see any more of the street name), and you see what appears to be "District Of..." on the bottom line where the state would be. This would mean they all live together and are from Washington, District of Columbia.
In 1973, the Lynyrd Skynyrd songs "Free Bird" mentioned by the characters and "Sweet Home Alabama" which was playing on the 8-track, hadn't been released yet. Both were in the process of being written in 1973.
The double yellow striping on the road outside the gas station, whilst permissible, is painted in the newer yellow/orange colors. The yellow/orange color was not in the MUTCD 1961 or 1971 standards. In 1973, while double yellow lines were permissible, they would have followed the 1961 color standards (as Texas didn't adopt the 1971 standards until later that year).
When Sheriff Hoyt climbs into the van to begin wrapping the dead hitchhiker's body with the plastic he begins wrapping the head first. Moments later, he is still wrapping the head but her whole body is already wrapped.
At the beginning of the movie, when the kids are driving in the van and they hit a bump, the body of the dead girl falls over onto the floor of the van, yet when they stop at the mill, the body is seen sitting up in the back of the van.
Leatherface's chainsaw is Husqvarna 359, which has a chain break on it. It is taken off in the movie to make it look like it was from that time period because they didn't have them on around then. However, after the first chase scene you can see Leatherface cutting trees with a chain break on it.
When Leatherface first begins to chase Erin and Andy inside the house and Andy turns aside the chainsaw with the tire iron, we see the saw from below and it is cutting length-wise through the floor boards. When we see the same shot from above the saw is cutting across the width of the boards.
Before Leatherface starts to attack Erin and Pepper in the van, Pepper enters the van and does not shut the door. When she exits the van to get away from Leatherface, she has to open the door to get out.
Erin's shirt is tied in a knot for the entire movie. However, twice the shirt is not knotted...when running to the closet in the second house her shirt flops around but is again tied as soon as she is sitting with the rats. It is again loose as she runs outside in the rain by the meat factory - tied as she is sitting in the truck.
When Leatherface is carrying Andy on his shoulder down the stairs to the basement, you can see the bill of someone's baseball hat to the right of the screen for a second as soon as the shot of the basement from the bottom of the stairs
In the beginning of the film, it states that the Massacre happened on Route 17 in Travis County. There is no route 17 in Travis County, TX, and the van in the beginning is entering Fuller, TX, and a girl screams "We're 3 hours from Dallas". Fuller, TX is 6 hours from Dallas, 8 hours from Travis County, and not along the way from El Paso, TX, which is where the girl says they came from.
While Leatherface sits and sews his skin mask, he is not really sewing. The hand wheel on the right of the machine does not turn. A sewing machine's hand wheel has to move if the needle moves, as they are synchronized.
When the Sheriff has the three characters prone in the dirt, he has their drivers licenses in his hand. As he starts to toss them down, the second license clearly states that it is an Arizona license. All three of the licenses are identical except for the picture. As he throws them down to them, he calls out the states of each of the owners. He first says "Arizona", although that is the second license, not the first one. He then says "Colorado" as he tosses down the Arizona license and finally says "New York" for the third.
Near the beginning of the movie, while the van full of teenagers is driving along the highway, there is a long shot of the van. In that shot, the van is visibly empty of any occupants other than the driver.
In the scene when Jedidia is helping Erin and Morgan escape the basement, you can see Erin climb the last four steps that lead outside. Then the camera cuts to Jedidia biting leather face on the hand. Then the camera cuts back again and we see Erin climbing back up those same four steps again.
The goof items below may give away important plot points.
As the Sheriff falls to the ground after being struck and thrown over the police car, he very obviously ends up face down on the pavement. In the next wide scene, as you see the car start to back up, he is motionless and still face down. There is a cut to a close-up, and the Sheriff is now laying on his back as he starts to get up, without ever having turned over.
After the hitchhiker commits suicide, and all the characters exit the van, the front passenger door is left open. Kemper is shown standing next to the open door, with his hands on his head. The camera cuts to Morgan for a moment, and then back to Kemper, who is in the same position, yet the door is closed.
When Erin finds Andy in the torture chamber, his toes are touching the keys of the piano under him. But after she kills him and kneels in front of him, it is clear that his foot is too high to touch the keys.