A Honda CR-V was driven into the shop with a bad tapping or knocking noise coming from the engine area. The noise attracted a lot of attention as the tech brought it in, because it’s not a normal sound. When the tech got it up on a lift, I thought it sounded like it was coming from right where the engine and transmission connect.
The tech removed the access cover between the engine and transmission and we could see that the flex plate, which is what connects the engine’s crankshaft to the transmission’s torque converter, was hitting the engine block in one spot every revolution of the engine.
After selling a new flex plate, the tech pulled out the transmission and we could get a look at what had happened. The entire center of the flex plate had broken out and was only still driving the torque converter because it was wedged in there, and a small piece had gotten itself stuck between the flex plate and torque converter, which is what pushed the flex plate into the engine block.
This picture shows where the flex plate was grinding away at the engine block, fortunately not enough to cause any problems.
You can tell which area that was because it’s discolored from the heat of scraping against the engine block, and you can see where the tiny bit of metal was stuck. I tried to match up the broken out center piece but couldn’t figure out how it originally fit. It’s surprising the car was even still driving.
The tech that fixed this said that the only thing he could see that could’ve caused this was that when the torque converter was recently replaced, the dowel pins that locate the transmission to the engine were missing, so it only had the bolts holding it in position, so it might’ve been just slightly out of balance from not being correctly located, which stressed and broke the flex plate over time.
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-Dan
Mechanical Malarkey 