How to Replace a Truck Transmission

When replacing a truck transmission, is it good to remember that the transmission is extremely heavy and awkward. Caution is in order so that it does not drop and cause bodily injury. You also should raise the truck high enough to extract the transmission from below once it is out. The floor jack will be in use holding the transmission, which makes it a poor time for you to realize the truck is too low.

Things You'll Need

• Floor jack
• Jack stands
• Set of wrenches
• Large drip pan
• 3/8-inch drive ratchet
• 3/8-inch drive extension
• Set of 3/8-inch drive sockets
• Large common screwdriver
• Hammer
• Rags for cleanup

Instructions

1. Remove the engine air cleaner. Remove the transmission kick-down or TV cable from the throttle linkage if there is one; these are found mostly on early model trucks. Disconnect the negative terminal on the battery, using a wrench. Raise and support the truck on jack stands. Place the drip pan under the transmission, and use a 13 mm socket to remove all but two of the transmission pan bolts.

2. Remove the last two bolts in the transmission pan slowly so that the pan will drop down gradually, allowing the fluid to drain into the pan. Remove the pan long enough to drain the rest of the fluid, then replace the transmission pan and loosely tighten all the bolts.

3. Remove the drive shaft, using a wrench to extract the four bolts in the yoke. Remove the gearshift linkage from the gearshift lever, using a wrench. Disconnect all electrical connectors. Remove the starter, using the appropriate-size socket. Remove the dipstick by pulling out the bolt in the bell housing that secures the dipstick bracket to the housing. Use the appropriate socket, normally a 15 mm. Place the common screwdriver under the bracket and tap it upward with the hammer to draw the tube out of the transmission.

4. Remove the front torque converter cover, using the appropriate-size socket. Remove the torque converter-to-flexplate bolts using the appropriate socket. Use the large screwdriver to turn the flexplate to get to the next bolt. Remove the bolts in the bottom of the transmission mount from the bottom center of the cross member, using the appropriate socket.

5. Place the floor jack under the transmission pan, close to the bell housing. Remove the two bolts on either side of the cross member where it is secured to the frame. Raise the transmission slightly and remove the cross member from under the truck. Lower the transmission a few inches, and remove the two transmission cooler lines on the passenger side of the transmission, using a wrench.

6. Remove all the bolts in the bell housing using the appropriate socket. Raise the transmission so that it is slightly lower in the rear. Use the large common screwdriver to pry the transmission away from the flexplate and engine. Pull the transmission straight out, being careful to support it properly and lower it to the ground.

7. Spin the torque converter in the new transmission to make sure it is all the way in. It has two slots that must be engaged, or the torque converter will be squeezed between the flexplate and transmission. When the torque converter is in correctly, it will be farther back than the bolt holes in the bell housing.

8. Place the new transmission on the floor jack and raise it up, being careful to keep it level and straight. Insert the transmission torque converter nose into the cavity in the flexplate, and start a couple bolts in the bell housing to help draw the transmission into the engine. Insert the rest of the bolts and tighten. Turn the torque converter to match up the holes with the flexplate, then install the rest of the bolts and tighten.

9. Install the transmission cooler lines on the passenger side. Raise the transmission slightly and install the dipstick tube and the bolt in the bell housing, securing the dipstick bracket to the housing. Raise the transmission enough to install the cross member and install the side to frame bolts. Install the rest of the parts in reverse order of removal, and fill the transmission with fluid. Run it through the gears and recheck the level. Fill as needed, running it through the gears after each addition of transmission fluid, until the dipstick shows the proper level.