Vibration and knock retard

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pinellas50

New Guy
Re: Vibration and knock retard

Big Mike said:
Try disconnecting your torque converter and push it twords the rear then start the truck to check if it may be the converter. While your at it you may want to look for the weight on the flexplate.
Click to expand...

I'll keep this in mind if I need to delve further. I understand the test but I think this is one that I would be afraid to do.
 
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pinellas50

New Guy
Re: Vibration and knock retard

I still haven't figured this one out. No one else has ever had anything similar?

With real balance issues like bent rods, missing weights on fly wheels, bad harmonic balancers, etc wouldn't there be a significant vibration at any rpm? A cracked flex plate would be banging pretty loudly wouldn't it? Wouldn't a bent rod be visible with the heads off the motor AND show up on a compression test?

And I don't understand while the vibration would completely go away when you take the serpentine belt off if it wasn't something to do with a front accessory. All the accessories spin free and true. The A/C clutch has a weird kind of gravely noise, you would only hear it with the motor off and your ear near the pulley, to it but it spins smoothly.

Could an A/C clutch do this? Bad belt tensioner? Something with the torque converter even though that works just fine?

If it comes to throwing parts at it, it would be nice to have a logical place to start. That logic is escaping me right now. Anyone have any expierence with the above listed scenarios to say if the symptoms of them were the same as what I have?
 
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MikeMcNair

New member
Re: Vibration and knock retard

this may sound silly, but are your motor mounts tight? how about the diff mounts?

i know i had something similar and it was the front transfer case mount to the frame. the one that is virtually impossible to get too unless you are a contortionist. (driver front suspension, right behind the top of the strut)

just a thought.
 
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pinellas50

New Guy
Re: Vibration and knock retard

Motor mounts are tight.

Front diff mounts tight? As far as I know. Would loose front diff mounts cause a vibration with the truck sitting still and in Park?
 
turbodig

turbodig

Active member
Re: Vibration and knock retard

Well, if you took the belt off, and have no vibration, the answer is there, someplace - one of the belt driven accessories. Loose crank pulley?

I'd pull the balancer, just for an inspection. They're notorious for slipping and/or losing the ring.
 
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MikeMcNair

New member
Re: Vibration and knock retard

pinellas50 said:
Motor mounts are tight.

Front diff mounts tight? As far as I know. Would loose front diff mounts cause a vibration with the truck sitting still and in Park?
Click to expand...

i am shooting in the dark because i am not there to actually witness things. also, i look for the free solutions before i spend money, so i am just throwing things out there.
 
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pinellas50

New Guy
Re: Vibration and knock retard

OK. Thanks everyone. Just looking to make sure that my deductive reasoning makes sense to others aside from myself. If/when I get free time I'll start looking over the free stuff. I still need to pop the inspection cover off of the tranny and inspect.
 
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pinellas50

New Guy
Re: Vibration and knock retard

I think I am bleeding from scratching my head now!

So I pulled the balancer to have a look see. It looked OK. Of course I had to but a new one to compare to the old one. So I put the new balancer on and found that the old one had slipped 4 degrees. So instead of having timing at 0 it was at 4.

While I was in there I noticed that the power steering pump sprung a leak. So I put a new pump and pressure side hose in.

Took it out tonight. I noticed kind of a wobble/vibration around 1500. I kind of think that was there before. But it smoothed out around 2K.

So once the motor got warmed up I took it for a WOT blast. I had DM running.

The vibration was still there but was much less violent in feel. Though it seemed to come on a little earlier. I backed out of the throttle when I felt it. DM showed no knock or spark retard this time.

I tried a light power break with it to see what it was doing. At around 1500 or a little higher the sound of the motor became wierd. I don't know how to describe it. It wasn't a rod knock, I've had that in other motors. This was kind of a chugging sound. Not really a pounding sound but you could tell that something was going on. It definately didn't use to do this before!

Now the vibration seems to be more noticable in most of the rpm range. So something changed tonight with this.

What the hell am I dealing with here? A bent rod? Torque converter/flex plate issue? How do I test? I'm still very hesitant to disconnect the TQ and start reving the motor with that thing just an inch away!

I'm going to reacquaint it with the jack stands and pull the inspection cover. I fully expect to find the weight in place on the flex plate.....crystal ball speaking. I'll probably go and pull plugs and do another compression test while I'm in there.

I could use anyone's input that has dealt with such a thing. I sent PM's to the authors of those threads I posted but never heard back from them.

The main questions I have now is how do you test for a bent rod or a bad TQ?
 
sly dvl

sly dvl

Ya, it's got a Turbo
Re: Vibration and knock retard

WyoSyclone said:
bent rod should show up in a compression test...
Click to expand...

Would it though? In theory you would have the same stroke, which should net you the same compression. I'm just thinking out loud here...

What if you did a cylinder balance test? If you take the engine up to 2000 RPM (or wherever the vibration is noticeable) and then killed one cylinder at a time by pulling a plug wire and noting the RPM drop. They should obviously all be the same. That would show a weak cyl. which could be causing a vibration. Again, just thinking out loud.
 
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pinellas50

New Guy
Re: Vibration and knock retard

I forgot to add that I also intend to pull the plugs and do another compression test. I pulled the wheels off last night so I can get to the inner fenders. I'm thinking I'll be looking for traces of oil on any of the plugs.

Oil pressure is still good so something like a spun or screwed up engine bearing isn't suspect in my mind. But who knows.

I guess the 4 degrees advance on the old balancer explains the lack of all knock retard now. Now that the timing is 4 degrees retarded from before. I think I'll check the timing as well to make sure it hasn't moved for some weird reason.

With torque converters, I have only ever seen bad ones start slipping really bad or just stop working all together. Has anyone ever seen one that works fine but something inside caused an imbalance?

I guess I'll keep poking at it. Thanks for the help so far. And please throw anyother ideas my way.
 
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pinellas50

New Guy
Re: Vibration and knock retard

All the plugs looked great with no signs of being lean or any trace of oil on them. Compression test results:

1) 155
2) 150
3) 160
4) 145
5) 155
6) 150

I forgot to wire the throttle body open when doing the compression test. But the throttle plate was closed when I tested all cylinders so I think the results should be relative. These are all within 5 psi from the last time I tested the motor with the last set of "fresh" heads on it.

I'll pull the tranny inspection cover next.
 
Mtn Z

Mtn Z

Donating Member
Re: Vibration and knock retard

To touch on another idea mentioned earlier, I would suspect bad front diff mounts could cause vibration. When I had my diff out to change the mounts, I had noticed my diff was rubbing on a section of the crossmember and had a decent sized notch in it from rubbing. So there was metal touching metal. The only problem this doesn't solve is the vibration when revving in neutral as torque isn't being applied to the diff. Just throwin around ideas I guess. :dunno: Any vibration issues I have ever had were from busted motors mounts and the stock propshaft. Good luck!
 
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pinellas50

New Guy
Re: Vibration and knock retard

Here is something I came across tonight. Mabey the same type of thing?

http://www.syty.net/forums/showthread.php?t=56730&highlight=flex

I got the transmission inspection cover off and took a look see. I don't see any cracks in the flex plate but in all the stuff I have read I don't think that I necessarily would. The cracks are usually up around the mounting bolts at the crank. The weight was on the flex plate.

I did notice that I could move the flex plate with only my hand. Thumb on the oil pan and pull/push the flex plate towards the rear of the truck. I could see it move though it's only a fraction of an inch. But I wasn't expecting to be able to move it at all.

I started the motor and at idle it looks like the flex plate is wobbling to me. I don't know if it is an optical illusion because of mabey the holes or converter bolts in it or not. But it really looks like it is wobbling. Like mabey the entire flex plate is bent. At anything higher than idle you don't see it but I'm pretty sure you wouldn't with it spinning so fast.

The converter bolts are tight. I messed with them for a few minutes trying to get them undone but then went to bed. It appears obvious that I have to push that converter back to get a better look at this flex plate. There is still no noise coming from this area.

Still no one that has dealt with something similar?
 
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pinellas50

New Guy
Re: Vibration and knock retard

Here's the big question. Well, info leading to it.

I unbolted the converter and slid it back. It went back far enough to see the mounting bolts. They are all tight and I don't see any cracks in the flex plate. I also see an alignment dowel pin thing amongst the flex plate bolts.

BUT.....the converter flops all over the place when it isn't bolted to the flex plate. I can see that there is a hub or snout on the front of the converter that goes into the crank shaft itself. I can push on the converter and this snout will go up and down/left and right in the crank.

So the question is, is this normal? Or is there supposed to be some sort of busing like a pilot bearing(yeah I know a pilot bearing is for a manual tranny) in there that prevents this snout from flopping around?

My guess is that the flex plate is flexible enough that it can flex around with the converter on it if this snout is not supported somehow. And is it a problem that the converter can move around so much on the input shaft of the tranny?

INPUT PLEASE!!!
 
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pinellas50

New Guy
Re: Vibration and knock retard

Well, I just found this picture:
sytrans2.jpg


That sure looks like some kind of bushing in the center of the crank. Correct?

EDIT: http://www.syty.net/forums/showthread.php?t=24570&highlight=crank
Well, I think I may have found my problem. That either that pilot was never put in there or for some reason it came apart and the pieces are no longer in there. Or it is in there and pulling the TC out that little bit that it moves is enough to pull it out of that pilot. I would just like someone in the "know" to agree with me before I go and pull that tranny out.

If I have to go through all this, I think it would make sense to put a better flex plate in there since I am assuming that this thing has been flexing all over the place. Is there such an animal?

I haven't tried running the motor with the TC pulled back. I'm still afraid to do that with the converter still very close to the flex plate. Or is there no chance for a problem doing this?

EDIT #2: I see how it works. The TC needs to slide forward to get into the pilot. Mine has a pilot in there. With the TC fully forward I can still move it up and down a fraction of an inch. Enough to get a clunk sound when it moves. Is this nomal?

If it is I'm out of ideas.
 
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pinellas50

New Guy
Re: Vibration and knock retard

I started the motor with the converter unplugged today. The vibration is still there and the flex plate looks like it is spinning true.

I then took the serpentine belt off and again the vibration is still there.

The vibration is noticably worse now and you can feel it through the body and the motor at all rpm's in neutral. Still no noise coming from anything.

My conclusion on this seems to be a bent rod or something else inside the motor is fubar. Not the conslusion I wanted but I can't think of anything else.

Can anyone think of anything else?
 
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pinellas50

New Guy
Re: Vibration and knock retard

This just keeps getting better.

I bolted the converter back up and buttoned up the bottom end. Then I decided to take Big Mike and Sly Dvl's idea on pulling plug wires. They all effected the way it idled. BUT. I found a bad one on #6. The wire to plug connector was all pushed way up into the boot, crushed, and even looked burnt.

I swapped out that wire for a used one I had and the whole vibration at any rpm went away. I can't believe there was no sign of this on the plug itself. Took the family out to dinner in it and it drove nice just like it always used to.

BUT, the high rpm vibration is still there. When it does this vibration, it seems like power drops off. But no codes are being thrown. So now I'm wondering if mabey it is the ignition breaking up at higher rpm.

I swear to God, this is the most frustrating vehicle I have ever owned!
 
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