eban808

Hey guys, Well after doing a search I believe my 91 camaro rs (305 automatic) may have a damaged flex plate. When accelerating from a stop it sounds like a bunch of rocks tumbling around behind my engine. When I start it up and put it in gear and makes that same sound, but kind of a knocking noise. It quiets down after warming up, if I put it in park or neutral, and when It's in over drive. I'm looking at ordering a new flex plate off of partstrain.com, and found a B&M replacment and a Hays replacment. I'll probably go with Hays, it's about $30 cheaper than B&M's. Has anyone used the Hays flex plate? Good or bad? Also wanted to double check that 153 teeth is correct for my car. Thanks

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vetteoz

And make sure it is for a '86+ 1 piece seal engine.
The earlier ones will not bolt up to your crank ( different bolt pattern )

Rolling Thunder

Well im kinda curious as theres not really much that can go wrong with a flex plate? From reading your post that diagnosis dosnt really sound right as u say it happens when you accelerate and when you start it and put it into gear. To me this implies it does not happen when in park or neutral (when you start it up) and concidering the flywheel is always spinning that doesn't make sense. Ignoring all that for a moment befor you buy a new flywheel perhaps you should inspect your old one as you may find its not the problem. Just my opinion though.

berlin305

I just went through this myself. If you put load on the flywheel it will do this if its cracked ect.. Mine did this. It would quite down one thing to also check to see if the transmission housing bolts are not loose as well or it will do the same thing as well. It sounds like crap and alot of dinging sounds and clunking. Mine actually had the whole center of the flywheel crack. This a common problem with the flywheels to get worn out and ring gears separate and the fly wheel cracks. SO your in the right track just inspect it. Before you remove tranny one way to know if your flywheel is bad. take the inspection flywheel cover off. put your hand on the torque converter and see if you and turn it. clockwise or counter clockwise with ease like its loose. if you can do this then flywheel is bad.

vetteoz

There is little load on the flexplate when out of gear ; it is only driving the pump.
When in gear and load applied, the crack in flexplate ( generally seperates around the crank hub boss ) will distort giving the well known noises.

eban808

Sorry for the late response, but thanks for all the info! I don't have a jack and my car's always parked in the street, so I haven't had a good chance to get under her and look. Im gonna see if I can take it to the auto shop at my school and check it out. Is it easy to access the flex plate? Or do I have to move the transmission or anything major?

basiccamaro

You can see and touch both the bottom of the flexplate and the bottom of the torque convertor by just taking the sheet metal flywheel inspection plate/shield off the bottom front of the transmission.
You can turn the flexplate and convertor and get a wrench on the TC-to-FP bolts by rotating it as you go around.

But to change the flexplate or convertor you will have to seperate the engine from the transmission either by loosening the transmission and moving it back (which means the driveshaft will almost certainly have to be removed) or by loosening and moving the engine forward (just about have to pull it, better to move the tranny back).
You will have to expose the FP- to- crankshaft bolts and have enough seperation of the engine and tranny to get a ratchet or wrench on the crank bolts and to get the TC pushed back enough for clearance. If you were removing the TC, you would need even more seperation.

An unfortunate by-product of the newer one piece rear main seal cranks is the smaller bolt circle and crank mounting flange for the flexplate. I personally like the older two-piece rear main cranks with the bigger flange, but alas, progress has taken us past that stronger setup. The one piece seal portion of the story is a better setup but I never had all that much of a problem with the two piece deal, so there you are. Any newer first gen small block high performance and even low performance stuff uses the one piece setup.