[cheepin]

Originally Posted by barry1982

Does it knock all the time, or just when driving? I had a weird experience years ago. Had a 78 Camaro Z-28. It had the 350/350 auto. One day is started "knocking" while accelerating. Let off the gas, it would quit knocking....??
I licenced mechanic told me it was a rod bearing for sure.....I was puzzled because a rod bearing should knock all the time. I took it home, and pulled the inspection cover off of the transmission, exposing the bottom of the torque converter/flex plate. Turns out my flex plate was cracked between the large "punch out" holes in two places. When the car would accelerate, the torque converter was pulling back too far, and ticking on the bell housing. This sounded EXACTLY like a rod knock. I pulled the tranny, installed a new $30 flex plate, and drove the car for eight years with the same engine.

I actually had about the same issue. Bought a 79 Suburban with a rebuillt 400. Started knocking 2 weeks after. I thought it was a bearing forsure. I crawled under it looking for lose anything. I could see daylight between the motor and trans. Turns out 3 bellhousing bolts fell out and the other 3 were lose. This cracked the flexplate around the crank.