Noise from flexplate while running- Stuck Starter Bendix? [FIXED]

[ratdude747]

Having some weird noises from my flexplate area when running. At low RPM it's a tapping noise. It becomes an intermittent clatter above 1000rpm or so.

Could this be a starter bendix that's not disengaging and constantly spinning the motor? Haven't pulled the starter yet. Might use this as an excuse to put in a PMGR if it's acting up. Not the first time I've had hiccups with the starter:

http://forum.garysgaragemahal.com/Screaming-Starter-Bad-Bendix-td82834.html#a82849

[Gary Lewis]

I've not heard a starter make a tapping noise.  But I have been told that flex plates can make a popping noise if they are cracked.

[ratdude747]

Oh, great. I'll shoot a video and post.

[ratdude747]

Video:



Seems to be more of a raspy squeak... but it's very noticable, more so than on camera.

The A/C is off. Noise seems to be coming from the bellhousing.

[ClayJ]

Doesn't sound like a cracked flexplate. Ask me how I know.

[ratdude747]

Good... I'll troubleshoot it more later. Good thing I have another truck to get around in.

One other note... this didn't start until I drove to pick up lunch... since it didn't go away by the time I left the drive-thru, I drove it home and swapped vehicles before returning to work.

[Rusty_S85]

ClayJ wrote

Doesn't sound like a cracked flexplate. Ask me how I know.

I dont know that sounds like it could be a cracked flexplate.  Ive seen them make come and go making noise.  Ive also seen them make different noises.  Hard to tell to be honest about the only way Ive been able to isolate is to try and lightly load the engine in gear to try and take the flex/slack out.

[ratdude747]

When I drove it to lunch/home, the noise would completely cut out under acceleration.

That said, I replaced the flexplate as part of an engine rebuild last year (original plate had chipped up teeth).

[rcarlisle]

Good luck figuring it out.  I have a tapping that sounds like valvetrain, but it has to be speedo cable.   Speed dependent and stops when the truck isn't moving.  I'll give yours a couple more listens to see if I can help more.   HAve you tried any kind of probe to see if you can isolate it anymore?  Derek on Vice Grip Garage used a bunch of 3/8" extensions put together to reach way down in the engine bay.  I never thought of something like that.

[ratdude747]

I just listened around and that led me to the bellhousing, passenger side (where the starter is).

One idea I had was to run it and measure voltage (AC and DC) between the starter side of the relay and ground... if it's backdriving, I should see something being generated? Or not because it has a field coil?

[FuzzFace2]

Rusty_S85 wrote

ClayJ wrote

Doesn't sound like a cracked flexplate. Ask me how I know.

I dont know that sounds like it could be a cracked flexplate.  Ive seen them make come and go making noise.  Ive also seen them make different noises.  Hard to tell to be honest about the only way Ive been able to isolate is to try and lightly load the engine in gear to try and take the flex/slack out.

I am kind of with Rusty as it could be a cracked flex plate.

When you changed out the flex because of bad teeth were the pins in the motor to bell housing?
If they are missing that can cause the flex plate to crack.

May want to check the converter bolts if tight.
I had them come loose, factory installed on a diesel, and it showed up sounding like a rod knock!
After freaking out and seeing the oil PSI was still good I started looking else where.
If the bolts are just starting to loosen might make a noise.
Dave ----

[ratdude747]

I had to go back to the build picks, but yet, both dowel pins never left the block the entire time.

---

Made a discovery... starter bolts are wicked loose... as in not even finger tight. Going to pull the starter once the exhaust cools down some more. Must have been one hell of a rattle to knock them loose like that!

(no they're not stripped)

[ratdude747]

Pulled starter, bendix was retracted. Reinstalled, no more noise.

Fixed. Maybe ought to check the torque in a week or go back and loctite them later. Grr...

[Gary Lewis]

Well, that's a cheap fix.  But you'd better check them like you said.

[kramttocs]

Glad to hear you found it and it didn't require any further disassembly (or cost)  

[ArdWrknTrk]

I had to helicoil the tapped hole in my Zf.
There was no way I was getting that lower screw tight enough to keep my starter from camming out of engagement.

[ratdude747]

That's the spec at work for custom Al and Cu parts. Might do that if it's convienient in the future (good access to drill and tap, or I find a self-drilling helicoil tap like my O2 helocoil kit).