Flywheel noise

[79dentside]

Hey guys, I am new here.

My 1979 GMC farm truck is clacking at idle pretty bad. I’ve had 2 mechanics look at the engine and the engine has no noise. They think that since my heat riser vacuum actuated rod to the bottom of the passenger manifold is siezed, that the flapper in there is most likely causing my idle knock.

this is a possibility, but I am looking to try to fix this one and done. I don’t like throwing parts and I could not hear a knock with my stethoscope anywhere on that exhaust bank/manifold. Do these heat riser valves “knock” if the actuated rod siezed in place? We have a definitive knock that sound like it’s from the bellhousing to me... but I’m not an expert.

**Here is a link to a video with the noise. Choke is on so it’s idling high**

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I am really thinking I got a cracked flexplate, before I do it myself, what am I getting into? Thanks!!

 

[Goldie Driver]

I think that flapper can only make noise if it is loose - know if it is frozen open, or closed ?

Flexplate = pull tranny.

Not bad on a 2wd, but not fun.

Not a mechanic and could not hear the noise all that well in the video as I am on my phone.

Good luck !
Britt

 

[79dentside]

I can’t distinguish if it’s stuck open or closed, the rod is 100% stuck though.

In idle, it clacks on and off. Fades in and fades out. You can put it in gear and sometimes it goes away. You don’t really hear it while driving. It’s usually just in idle.

I am going to pull the bottom cover tonight and see if I see cracks or if it wobbles.

how do you pull the tranny without damaging the pump seal? Or is that a relevant concern?

thanks!

 

[79dentside]

Would that flapper cause a LOUD knock???

 

[Snoots]

IMO it's not the flapper.

Pulling the inspection plate would help and also disconnect the ground cable and get a buddy to turn the engine by hand while you inspect the flexplate.

 

[Goldie Driver]

I can’t distinguish if it’s stuck open or closed, the rod is 100% stuck though.

In idle, it clacks on and off. Fades in and fades out. You can put it in gear and sometimes it goes away. You don’t really hear it while driving. It’s usually just in idle.

I am going to pull the bottom cover tonight and see if I see cracks or if it wobbles.

how do you pull the tranny without damaging the pump seal? Or is that a relevant concern?

thanks!

Hopefully it is stuck open since that is the relaxed position by default.

Been a while since I pulled a tranny, but it seems like you can just drop the tranny with the converter still on it .

But, if it is out, changing the seal is cheap insurance. I think Goldie is leaking there - $3.97 per quart of tranny fluid is cheaper than having the transfer case and tranny pulled to change it, though, so she will be leaking for a while.

 

[79dentside]

Hopefully it is stuck open since that is the relaxed position by default.

Been a while since I pulled a tranny, but it seems like you can just drop the tranny with the converter still on it .

But, if it is out, changing the seal is cheap insurance. I think Goldie is leaking there - $3.97 per quart of tranny fluid is cheaper than having the transfer case and tranny pulled to change it, though, so she will be leaking for a while.

Good tip... this is a 2wd. I have a buddy with a 90- something Silverado that gushed tranny fluid out of the pump seal, that would be wise to replace.

Any tricks for pulling they tranny without a lift??

IMO it's not the flapper.

Pulling the inspection plate would help and also disconnect the ground cable and get a buddy to turn the engine by hand while you inspect the flexplate.

I don’t think it’s the flapper either, which is why I’m here haha. She’s sitting outside and it’s raining, so checking the flexplate isn’t going to happen tonight haha.


Thanks for the help guys!

 

[Goldie Driver]

Last one I did was over twenty years ago on a 4wd Ram Charger cause a freeze plug crapped out.

IIRC we did not have to pull the flexplate to get to it.

Anyway, 3 guys on 3 floor jacks lowered the tranny and transfer case as an assembly still bolted to the transfer case cross member that had been unbolted from the frame.

Actually went smooth.

2wd one guy could do it by dropping it down on an unmounted tire (carefully) but 2 people might be able to manhandle it down.

Not sure how low a transmission Jack goes, or possibly a motorcycle jack, or if there are places that rent them, but it might be worth asking.

Bound to be someone here with better knowledge to answer you.

So, free bump.

 

[79dentside]

I have news fellas... got a little wet but I wanted to know. I was right.

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This could be rough!! Not what I wanted to fix, but it’s better than an engine!

 

[79dentside]

Here is another video of what the ol’ girl is doing...

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[Snoots]

Step one = BE SAFE
Don't ever think you can do this (pull a tranny) by yourself.

If you do pull the tranny install a new front seal ANYWAY, even if it's not leaking.
And a new rear seal wouldn't hurt either.

GOOD CATCH on the crack!

 

[79dentside]

Step one = BE SAFE
Don't ever think you can do this (pull a tranny) by yourself.

If you do pull the tranny install a new front seal ANYWAY, even if it's not leaking.
And a new rear seal wouldn't hurt either.

GOOD CATCH on the crack!

To be honest, I know some trans techs that I may just let have at it. This would take me the better part of a day at least, then if I screwed something up I would kick myself.

I think I broke it worse about a week ago. The flexplate used to knock, but knock quieter than it does now. I had to drive it on the highway for about an hour and a half and it has something like 4.11’s it 4.56’s so it creeps up to 4,000rpm on the highway, I try to keep it at 3,000 without clogging the highway.

I’m wondering if this trip really finalized her. I’m uncomfortable driving it right now, it knocks LOUD.

Will be a few weeks before she can get in, should I just let her sit? I don’t want to cause any damage.


Thanks

 

[Snoots]

Bite the bullet. Let it sit.

 

[Preston]

Remove the driveshaft, Take two pieces of all thread and pull the bolts out of transmission and pull it bacK an inch just enough to get a nut on each side of your block and then slide the transmission and torque converter slowly back swap out the flex plate and replace then slide everything back one man job. Of course use proper jack stands and be safe, usually 12” of all thread will work take it slow and easy. Might have things out of order but you can figure it out. Have fun

 

[Goldie Driver]

Remove the driveshaft, Take two pieces of all thread and pull the bolts out of transmission and pull it bacK an inch just enough to get a nut on each side of your block and then slide the transmission and torque converter slowly back swap out the flex plate and replace then slide everything back one man job. Of course use proper jack stands and be safe, usually 12” of all thread will work take it slow and easy. Might have things out of order but you can figure it out. Have fun

That's a hella good idea!