Loud Knocking Noise Coming From Rear of Engine...

[GEJ]

Of course stay way,way,away from the flexplate,but get it up on a lift with the inspection plate off and run it.If it has run-out,either the bolts are loose or the flexplate is cracked.Pay the repair shop for 1/2hr lift time,take it home and get busy.

[SoCalli V8]

All the flexplate cracks that I have seen have been cracked from one crank bolt-hole to the next.

Some times the flexplate to crankshaft bolts have been loose, and other times they were really tight (over torqued)

If this does end up being your problem, replace all the bolts and torque them to spec (pm me for that torque # and the correct proceedure if you need to)

[GEJ]

One other thing to consider is if the flexplate is moving around that much,I would think is makes sense that it is wearing on the tranny's front seal and on the starter gear.I had one on a Corvair yrs ago and I kept throwing starters in it until it started breaking off the nose of the starter from binding. It was a expensive lession well learned how those flexplate starter gears and the starter gears have to mesh when I was a kid.

Let us know what you find.

[9dawgs]

UPDATE: Ok, here's the latest info. I climbed under the van with the engine idling and put one end of a wooden rod to the engine and the other end to my ear. I moved the rod from front to back and determined the noise was strongest in the upper rear section of the engine. Starting to sound like lifter issues? Anyhow, I let it warm up good to see if things would change concerning the noise. Nothing changed. I got in and drove it around the block about 2 miles. The noise went totally away. Nothing...not even a little bit. I pulled back into the driveway and listened again at idle. Still no noise. I know though that when I start it back up after it's been sitting for a while it will again make the noise. Any suggestions??

Tuesday I will drive it to my friends shop to see if he can diagnose the problem. Hopefully is won't be too major. I'll keep you posted. Again thanks for all the good tips and terminology

[kc5gxl]

Howdy;

Sounds like a lifter that is bleeding down over night. A flexplate noise will not go away as it warms up, though it may change sound a bit depending on whether it is in gear or not.

If it is a lifter that won't hold it's charge, it will need to be replaced. Just use your stethoscope to find which one it is.

Good detective work!

Drive safely,

Dan Harriman
Orange, Texas

[6spd_monte]

I agree that it sounds like a lifter, but rather than trying to pinpoint the one that has failed I would just replace the whole set. Better than having to do it again when the next one fails.

[GEJ]

Take a close look at the cam if it turns out to be a lifter.I wouldn't think that would be a issue with the lifter spider doing it's job,but it won't hurt to double check that.