Vibration 2200 - 2500 RPMs

Logan

Logan

Member
I looked around and found some similar posts but nothing really on the spot so here goes.

I am still breaking my truck in, it has about 400 miles on the new engine and I have a slight to moderate vibration at 2200-2500 RPM range. I have narrowed it down to the drivetrain (engine/tranny) because it does it at different speeds and immediately goes away if I put the truck in Neutral and coast.

I am guessing it is the flexplate. The one that was in the truck refused to come off of the old engine so I used one I had in the parts bin from another project. Same tooth count, same weights (from appearance) and all but something is telling me that is where my problem lies.

Before I go ripping the tranny back out does anyone have any other advice? Could timing cause it? Or some other odd ball thing I am not thinking of?
 
Logan

Logan

Member
Re: Vibration 2200 - 2500 RPMs

I checked the TC bolts today and no joy. Still have a little vibration but I have more issues. Since I apparently don't have the right knock sensor in (New GM one comes in on Monday or Tuesday) the computer is pulling maybe 5 or 6 degrees of timing which is giving me a pinging noise somewhere in the bottom end so I may have identified one problem but we will see once I put the new knock sensor in.

The joys (headaches) of tuning a new engine...
 
Logan

Logan

Member
Re: Vibration 2200 - 2500 RPMs

Update. So I still have this transient vibration. I am looking for ideas. It is only under throttle. If I am going above 60mph it will vibrate slightly but it goes away if I let off.
 
coupecustom

coupecustom

Member
Re: Vibration 2200 - 2500 RPMs

So if you've limited it to drivetrain, then consentrate on any joining rotating part. U-joints, drive shaft balence, torque converter, ect.
You mentioned that the old flex plate wouldn't come off, so you had to use a new/different one. Since the flex plate connects directly to the torque converter....that's my guess of where your vibration is. Not a fun task, but the way their built leads to vibration when only slightly damaged. I would also guess torque converter, since they often will stop vibrating when running at higher RPMS.
 
Logan

Logan

Member
Re: Vibration 2200 - 2500 RPMs

I did a new flex plate about a month ago and as fun as it was, no joy. V8 GT, I am gonna try that today. I also am doing u joints in the drive shaft because I can only imagine how long they have been in there.
 
Big Mike

Big Mike

New member
Re: Vibration 2200 - 2500 RPMs

What does your build consist of, did you get the crank balanced to your new rotating assembly, did you clearance for the rods if they are Eagle rods? You sure your tires are not flat spotted from sitting?
 
Don W.

Don W.

Stab it and steer it
Re: Vibration 2200 - 2500 RPMs

Couple of ideas. What frequency is the vibration? IOW does the vibration follow engine RPM or road speed? Based on your description RPM would be the answer. So, can you produce the vibration while stopped in neutral? In gear?

"I have narrowed it down to the drivetrain (engine/tranny) because it does it at different speeds and immediately goes away if I put the truck in Neutral and coast."

This statment dosen't make sense. If it was drivetrain then it would still be there when you went to neutral.

All that being said and making the assumption you can produce the vibration while parked then disconnect the torque converter, slide it back and see if the vibration is still there. If so it's the motor, If it 's gone then it's the TC.

Make sense?

HTH
 
Logan

Logan

Member
Re: Vibration 2200 - 2500 RPMs

Problem solved! Took out the prop shaft and discovered the needle bearings in 2 of 3 U joints were lubricated with rust and pretty much trashed. New U Joints and it is running like a champ!
 
Don W.

Don W.

Stab it and steer it
Re: Vibration 2200 - 2500 RPMs

Just to be honest, I was off a little. Drivelines CAN and often do produce vibration when under load and not when coasting. My bad.
 
Logan

Logan

Member
Re: Vibration 2200 - 2500 RPMs

^ it happens. Any idea was good at the time. Either way, I'm just glad I got her back on the road.
 
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