Tips on Buying a Flex Plate
Because it connects the engine to the automatic transmission, a broken flex plate is a problem you should not ignore. Thankfully, replacement flex plates are not that hard to find nowadays. Here, we are going to give you some tips on finding the right flex plate for your car's transmission.
What to look for
Of course, when buying a flex plate, it is important that it matches the specifications of your car. Some of these include:
- Gear teeth. Different cars have different number of gear teeth on their flex plates. Cars that have a Ford 289 engine, for example, have flex plates with 147 to 157 teeth, while those on small block Chevy engines have 153 to 168 teeth.
- Diameter. The flex plate needs to be in the right size in order to mate properly with the starter motor. Thus, the replacement flex plate should be the same diameter as that of the old one. Also, the flex plate's diameter correlates with the number of teeth it has: the more teeth on the flex plate, the bigger the plate becomes.
- Imbalance weight. Flex plates are balanced with both the engine and transmission, so make sure to check the imbalance weight of the flexplate before buying one. You can usually find the weight identification on the face of the plate, opposite the drain hole.
- Starter bolt holes. Large plates are compatible to starters with either offset or staggered bolt holes, while smaller plates are designed for starters whose mount holes are adjacent to one another.
Performance flex plates
When shopping for replacement flex plates, you may have encountered performance or heavy-duty flex plates. This type of flex plate is made of thicker steel compared to the OEM flex plate, making it less likely to crack under high torque and RPM conditions. What's more, heavy-duty flex plates also zinc plated for additional corrosion resistance. However, because they do not match the exact specifications of your car compared to OEM flex plates, there is no guarantee that performance flex plates will work properly in your car's transmission.
How to Replace the Flex Plate in your Transmission
There are many things that can cause the flex plate in your engine crankshaft to crack. The most common is the misalignment of the gears between the engine and the automatic transmission, causing the flex plate to bend and eventually crack. Excessive crankshaft flange run-out can also lead to the flex plate to break. But whatever the cause, a broken flex plate should be replaced immediately to prevent any accidents on the road.
Replacing a broken flex plate involves a lot of tools and removing a lot of components. So if you are not confident with your skills in auto repair it is best to leave the replacement to trained professionals.
Difficulty level: Difficult
- Floor jack
- Jack stands
- 1/2 inch air impact gun/Socket and ratchet set
- Flat-head screwdriver
- Large prybar
- Adjustable wrench
- Socket extension
Step 1: On a level surface, raise the vehicle and place jack stands underneath for support. Afterwards, remove the front wheels using the air gun or a socket wrench.
Step 2: Detach the brake caliper from the wheel. Hang the caliper on the spring and tie it with bailing wire so it won't hang by the hose.
Step 3: Remove the two large bolts that attach the strut to the spindle, followed by the center nut on the axle end in the center of the rotor.
Step 4: Once the bolts have been removed, separate the spindle from the strut by pulling them apart by hand. You can do this by pulling the spindle outward and pushing the axle in toward the engine.
Step 5: Insert the prybar between the transmission and the inner CV joint and pry the joint out. Do the same to the other side.
Step 6: Disconnect the negative cable from the battery and remove the starter bolts. Take out the wires from the rear of the starter and pull out the starter off from its mounting.
Step 7: Remove all the wiring from the top of the transmission bell housing. You can do this either by disconnecting the connectors or removing the bolt that holds the harness to the transmission. Once all the wiring is removed, detach the speed sensor. Remove the bolt on the rear of the transmission and then pull the sensor up and out of the transmission.
Step 8: Remove the air cooler lines from the front side of the transmission. Cap the hoses to prevent any leaks.
Step 9: Remove the bolts from the top side of the bellhousing and take out from transmission shift cable by prying it off of the lever. Use a socket extension if you can't reach the bolts.
Step 10: Remove the lower torque converter and then the bolts that connect the converter to the flex plate.
Step 11: Place a jack under the transmission pan and raise it just enough for it to come in contact with the pan. Once that's done, remove all the remaining bell housing bolts and pry the transmission away from the engine using a screwdriver. With the transmission balanced on the floor jack, lower it down to the floor.
Step 12: Remove the bolts in the center of the flex plate and take out the plate itself.
Step 13: Install the new flex plate. Make sure that the convex circumference of the plate is facing away from the engine. Once it's attached, replace all of the items in reverse of how you removed them.