Vibration in cab

[skokie]

I was letting the truck run today and I noticed while the truck was in park when I revved it up to 15-1600 I felt a mild vibration at around 11-1300 then it went away and came back to 15-1600. At 1700 it was gone. I was not moving so its not the driveline. I got out and popped the hood and revved the engine by hand and could not see any noticeable vibration. When the engine was out it I replaced the flexplate on it and put on new arp bolts as well. It feels like its coming from the steering wheel area. Has anyone had this problem before?

[skokie]

Forgot to add that had the same vibration before I hooked the tranny up to the motor.

[skokie]

Ttt

[OldCreek]

It's coming from the near empty can of coors sitting on the dash. Drink the rest and replace with a full can to weight it down. It's been proven that the harmonic resonance of aluminum cans, especially coors, occurs at that precise rpm range.

Sorry, I've nothing really to add to your question.
Start grabbing items around the column/dash and see if you can make the vibration go away.

[HomerJ]

Skokie,

What is your engine setup (v8, i6, intake, carb, etc)?

[skokie]

Engine is a crate 350. Carb is a qjet, Edelbrock 2101 intake, ramhorn manifolds.

[Huck]

Vibration can come from a lot of things--harmonic balancer, motor mounts, torque converter (mounting bolts, etc.) Does the truck react to this vibration when driving?

[skokie]

Motor mounts, balancer, torque converter, bolts etc are all new. This vibration is there with the truck sitting in park. Also I separated the tranny from the engine and had the same vibration.

[WorkinLonghorn]

Before we go any further,are you saying that the idle is smooth as glass and there is a vibration unrelated to a cylinder occasionally missing,and that it is always present?

[skokie]

Yes. Idle is good. But when you rev it to 1100-1400 you have the vibration after1500-1600 it goes away.

[WorkinLonghorn]

The new flex-plate? The balancer? Engine not balanced correctly?

[skokie]

Balancer and flex plate are new. Not sure about the engine. It is a crate 350.

[WorkinLonghorn]

How bad is it?

[skokie]

On a scale of 1-5 I would give it a 2

[WorkinLonghorn]

Well,I guess all you can do is double check everything including the motor-mounts,check everything for balance including the above mentioned parts new or otherwise,plus the fan.Then if you are 100% sure it's none of these and you have put your hand over the exhaust pipe to see if there is the slightest miss going on (an engine anylizer works too but they charge $40 for that test around here).Then if you still have this vibration on a new or rebuilt motor,I would have to say that it was balanced wrong internally.

[beautimus]

ok, i'll chime in here but only guessing, and its mostly the obvious stuff.
you say that you feel it, but are you hearing a vibration noise as well?
i have seen exhaust systems that contact frame members cause a noise and noticeable vibration at just off adle like that when parked, but not get any rattle at all in gear or at hiway speed. the motor tends to lift some on the mounts just above idle, and can let that happen.

other wise i gotta think its in the motor or tranny. just my guesses.
good luck !

[Chevyholic]

I have the same issue with my truck. Look real close at your bottom pulley. I had to play around with mine for quite some time, but i finally rev'd the engine and noticed that my bottom pulley appeared slightly off balance in that RPM range. Granted, I've done nothing about it, yet, but that's where I see the problem.

I plan to get down there and remove the pulley to see if it is the pulley, or shaft and will work my way back from there.

Sound's exactly the same though, at least same RPM range and behavior.

[skokie]

Thanks for all of the suggestions. I am going to check the pulley problem tonight. One thing that keeps coming back to me is that I feel it in the steering wheel which is right next to the power steering pump. I am going to take the belt off of the power steering pump and see what happens. If that doesn't get rid of it then I will remove the alternator belt. If that doesn't do it then the pulleys are coming off. Also I will check the exhaust and see whats going on there as well.

[skokie]

Ok here is what I did. I did not get to the crank pulleys. I did remove the power steering and alternator belts and same vibration. But I noticed something tonight. Reminder this vibration is there when the truck is parked and running. The vibration felt like it started in the engine of the truck at 1100-1300 rpm and it 1500-1700 it moved to the back of the seat. Tomorrow I will try taking off the crank pulleys to see if that helps anything.

[HomerJ]

I had a vibration in my engine before I pulled it out to send it to the body shop. On the engine stand, I found 2 valve springs that had the top winding broken. The engine is still on the stand (and will be for some time), so I can't say if replacing the springs fixed the problem, but I feel confident that it will.

Just something else to check....

HomerJ

[skokie]

Ok after spending some more time looking at the torque convert and flywheel I decided to remove the tranny from the equation. Guess what. I can see a wobble in my flex plate. I made some calls and found out that some flexplates have weights and others dont. My does not. Not sure if that is the issue but I will be taking it down to a friends tranny shop to have him check it out as well. FUN FUN FUN....

[Eddie H.]

If you have a 350, there shouldn't be any weights on the flexplate since it is internally balanced ( unlike a sb 400 which is externally balanced and has a weighted flexplate)
Many engines have a normal resonance that is only noticeable at certain rpm ranges ( such as revving an unloaded engine while it is in park ) that doesn't affect the normal operation of the engine while driving under load.
If you had an actual engine out of balance problem, it would likely be much worse than what you're describing.
Unless it is noticeable whan driving, I probably wouldn't worry about it.

[skokie]

Yep I am kinda thinking that as well plus if something does happen to the 350 then it gives me the perfect excuse to built the 327 I have out back

Originally Posted by Eddie H.

If you have a 350, there shouldn't be any weights on the flexplate since it is internally balanced ( unlike a sb 400 which is externally balanced and has a weighted flexplate)
Many engines have a normal resonance that is only noticeable at certain rpm ranges ( such as revving an unloaded engine while it is in park ) that doesn't affect the normal operation of the engine while driving under load.
If you had an actual engine out of balance problem, it would likely be much worse than what you're describing.
Unless it is noticeable whan driving, I probably wouldn't worry about it.

[Boog]

If you still have the vibrations during your test drives then it might be worth getting concerned about. By the way does it have an exhaust system on it yet?
My 69 only has headers-collectors-flows. It's real loud right now and at certain rpm it makes things vibrate around in the bare cab floor. It is only temp of course so I can move it around in the shop.

[skokie]

Yes it does have dual exhaust on it. If it does vibrate when I drive then I will be taking it to a friend at his tranny shop.