Schiavonske1013

iTrader: (1)

Here’s an interesting one, so I’ve been having a vibration issue for as long as I can remember, first noticed probably a year or so ago while driving. Didn’t give it too much thought at first. Ran through tires, rims, driveshaft etc and seemed okay but still there. Didn’t seem to cause issues. Fast forward to this past February and my old 4l60e goes boom. Now in the back of my mind I’m thinking vibration must have been the trans. Well one 4l80e swap later and it’s still there. Finally started taking time to actually diagnose.

First thing I notice is it always happens at 2300-2500 rpm. Never ever different, always the same rpm every time. Also it happens in park, neutral, drive. Again every time. In the 4l80 swap the flex plate and torque converter obviously were changed, so I’m not looking at that since it never changed after swap. Now I do have an mp112 blower, can’t remember as it’s been on more than a year, but no idea if this was around before adding it. Removed the belt, had someone hold bypass open and hold blower pulley just to eliminate any accessories or car gods help me, the blower. Vibration still there, same spot, every time.

Trans mount was done when the swap was done, motor mounts are original, but the motor is staying in place as it should. I’m leaning toward a balance issue, I’ve never seen a bad motor mount vibrates only at a specific rpm, especially at a relatively lower rpm. Have a good scanner and checked misfires, nothing. I’ve never seen a vibration at such a specific rpm like this that is unaffected by engine load etc.

Anyone have any thoughts?

Schiavonske1013

iTrader: (1)

Forgot to say it also happens whether I’m giving it has to raise rpms or letting off has to slow them down. Ether revving up or letting them fall, as soon as it passes through that range, it vibrates and then stops as soon as it’s out.

1FastBrick

iTrader: (17)

Last time you did plugs and wires?

Who tuned it?

Have you asked them to look into it?

Schiavonske1013

iTrader: (1)

I’m on the trucks 2nd set of wires right now. First set were the originals, I re-used them when I went to tr6s after the blower install, didn’t damage any pulling them off the original plugs. When I went to long tubes I was stupid and cracked a couple of the plugs by smacking the header against them, I slipped, long story. All I could get on short notice locally was tr7s and I went ahead and got an ac delco wire set and just changed them. I know the vibration has been there the whole time. Been through 2 different tuners as well, a loca guy who used efi live who became too busy to make changes in under 3 weeks and recently atomic has been doing mine with hpt. I did send him this thread so I didn’t have to type it all out twice. I put that on the back burner as well thinking what’s the likelihood it stuck around after 2 diffferent tunes, but I’m an engine guy more than tuning so i could be wrong.

ZO6Ted

I don't recall if these are internally balanced or not. Harmonic balancer? Pinned?

rennat_2006

iTrader: (10)

Hang some weight on the exhaust about where the cab and bed meet. Sandbag, leadbag for shooting, anything you can with some decent weight on it.

I dont think the 5.3 had the issues but i know the 6.0 did when i was at the dealership. They had a reasonance vibration that under the bulletin you would install a weight to the exhaust in a certain location to stop it.

Schiavonske1013

iTrader: (1)

Interesting, hadn’t heard that one about the exhaust.

If I remember correctly the are internally balanced and instead of a harmonic balancer have a dampener but I could be remembering incorrectly.

Schiavonske1013

iTrader: (1)

So did a crank relearn just for the heck of it since I have a snap on solus and checked misfire data and not a single one registering. At this point I’m leaning toward balance as it does not appear to be tune related either.

BudRacing

iTrader: (3)

From what I've read and experienced, vibrations are common on the LS platform in this RPM range.

Have you tried the weighted bag on the exhaust? A band-aid like that may be your best bet. Even Land Rovers use weights on the exhaust.

They are internally balanced, but the crank dampener pulley is there to mitigate some vibes that are inherent. Swapping my pulley out for an ATI superdamper didn't really have any noticeable affect on my engine's vibrations, but I also have poly motor mounts. My first thought, however, was motor mounts when you described the problem. Even if they look good, there's a chance they're not. If they're original, I'd recommend replacing them.

Schiavonske1013

iTrader: (1)

I plan on going through with mounts anyway, at 118k they’ve gone through enough. Thankfully they are not as bad to do on these as they are on the newer trucks. I’d rather not deal with replacing the pulley at the moment.