How/check flexplate for crack/bolt knock? - Turbo Dodge Forums : Turbo Dodge Forum for Turbo Mopars, Shelbys, Dodge Daytona, Dodge SRT-4, Chrysler PT Cruiser, Omni and more!

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post #1 of 21 Old 02-22-2011, 07:42 PM Thread Starter
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How/check flexplate for crack/bolt knock?

I need to confirm if the knock I'm hearing is coming from the flexplate/bolts.

It occurs in park and gear both at idle and while driving, especially under load.
However, over 2700 + rpms and on the highway it seems to go away.

Do I have to pull the engine to inspect the flexplate, or is there a panel I can open for a proper view? Would a stethascope on the trans house be definitive? Where can I get install instructions, my (haynes, chilton) manuals don't describe the procedure, or maybe they call it something else?

I've been assuming I need a short block, but if I buy the block and during install find that I had a broken flex plate or loose bolts I'll be pissed.

Last edited by park9472; 03-07-2011 at 06:23 PM.
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post #2 of 21 Old 02-22-2011, 07:52 PM
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Re: How/check flexplate for crack/bolt knock?

From the description, sounds like the flexplate.

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post #3 of 21 Old 02-22-2011, 08:08 PM
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Re: How/check flexplate for crack/bolt knock?

there is an inspection cover you can remove to look at the bottom part of the flex plate there you can check the bolts for the converter and tighten them if loose. If the flex plate broke that can not be seen from the cover area BUT there are clues look at the picture posted above. Look for the rust streaks like in the picture. rust streaks won't be there if things are ok.
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post #4 of 21 Old 02-22-2011, 08:20 PM
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Re: How/check flexplate for crack/bolt knock?

if its broke you will either have to remove the trans or the engine, whichever is fine with you, (easier to remove the trans IMO)
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post #5 of 21 Old 02-22-2011, 08:31 PM
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Re: How/check flexplate for crack/bolt knock?

The one in my car was cracked. I just welded it up on both sides. Then ground it off. It wasn't as bad as the one pictured here tho.
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post #6 of 21 Old 02-22-2011, 08:45 PM
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Re: How/check flexplate for crack/bolt knock?

that might work if you flexplate is cracked, if you know somebody that can weld
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post #7 of 21 Old 02-23-2011, 02:29 PM Thread Starter
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Re: How/check flexplate for crack/bolt knock?

The metal face shield on the trans where it faces the block and oil pan has one little bolt at 6 o'clock but is also pinned behind the front motor mount and a rear bracket (as pictured).

Which bolts do I remove, or do I have the wrong shield?
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Last edited by park9472; 02-23-2011 at 06:05 PM.
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post #8 of 21 Old 02-23-2011, 06:21 PM
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Re: How/check flexplate for crack/bolt knock?

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Originally Posted by park9472 View Post
The metal face shield on the trans where it faces the block and oil pan has one little bolt at 6 o'clock but is also pinned behind the front motor mount and a rear bracket (as pictured).

Which bolts do I remove, or do I have the wrong shield?
you got the right bolt and you will have to remove the mount bolts and what ever else to remove the plate.
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post #9 of 21 Old 02-23-2011, 06:40 PM Thread Starter
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Re: How/check flexplate for crack/bolt knock?

Is the inspection cover sloted so I can just loosen the bolts, or full removal?
What is holding the trans and engine together at that point?
I need to put blocks under the engine and trans, i assume?
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post #10 of 21 Old 02-23-2011, 06:52 PM
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Re: How/check flexplate for crack/bolt knock?

Yea you gotta pull the front mount bell housing bolts, and I think there was a bolt towards the rear of the bell. There is probably a bracket coming off the block to bell housing back there. Just unbolt everything on the bottom half of the bell housing. Once you get all the bolts out, it's not just gonna fall out. You'll have to pry it down out with a screw driver. They're kinda jammed up in there. I didn't put a jack under it when I checked mine. If you're lucky, the torque converter bolts are lose. I wasn't so lucky, later on I found that my engine had a broken piston.
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post #11 of 21 Old 03-02-2011, 03:42 PM Thread Starter
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Re: How/check flexplate and engine for knock?

The flexplate bolts and surface look fine...

So now I need to take the next step in sorting out this knock

It occurs in park and gear both at idle and while driving, especially under load.
However, over 2700 + rpms and on the highway it seems to go away. It also seems different at different ambient temperature or just randomly different at different times when I drive it.

I pulled each plug cable before cranking engine...In all cylinders the knock was still there...I've forgotton what this means? What is my next diagnostic step?

Could a bad lifter also cause a sound like a lower end knock?

Despite what seems like a lower end knock, I don't get any read on the oil pan with the stethascope, only on one side of the valve cover.
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post #12 of 21 Old 03-02-2011, 04:16 PM
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Re: How/check flexplate for crack/bolt knock?

The lifters are noisy in my car to, I'm starting to think it's just how these cars are. The new engine only has about 2000 miles on it.
When I bought my daytona. It had a noise in it, and was pretty gutless. I found some oil in the intake. You might wanna do a compression test. I did one and found a dead cylinder. The 2.5s had some piston problems, mine was broken.
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post #13 of 21 Old 03-02-2011, 05:01 PM Thread Starter
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Re: How/check flexplate for crack/bolt knock?

Quote:
Originally Posted by Zero Tolerance View Post
The lifters are noisy in my car to, I'm starting to think it's just how these cars are. The new engine only has about 2000 miles on it.
When I bought my daytona. It had a noise in it, and was pretty gutless. I found some oil in the intake. You might wanna do a compression test. I did one and found a dead cylinder. The 2.5s had some piston problems, mine was broken.
I have a compression gauge which appears to screw in to the plug port that reads 0 to 300 psi.

what numbers am i hoping for?
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post #14 of 21 Old 03-07-2011, 05:23 PM Thread Starter
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Re: How/check flexplate for crack/bolt knock?

Still tracing down a knock: flexplate apears ok
compression is 130#1 120#2 130#3 120#4

Not a dead cyl, but...

Could a dead lifter cause a sound like a knock (not a click)?
I also read the knock through the valve cover by stethascope...none in the oil pan.
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post #15 of 21 Old 03-07-2011, 09:10 PM
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Re: How/check flexplate for crack/bolt knock?

If it's a rod knock then while listening with your stethoscope pull one plug wire at a time (sliding a test light down between the plug wire and boot also works). If it's a rod knock the knock will go away when you kill the cylinder.

To really check your flex plate you've gotta take it out. Your just not gonna see everything from peeking through that lower cover. When you have it in your hands look for a redish powder in a line. The cracks can be super fine and hard to see. The plates usually crack around the crank like the picture shown, but those rusty streaks aren't aways there.

We checked everyone when we put a transmission in when I worked for a school bus company. They cracked alot. And would knock just like a rod knock.
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