teesee150

iTrader: (32)

I've been stumped on this one and was hoping someone could help out. I've got a 2004 Sierra 1500 that has a bad vibration whenever the RPM is between 3000-4500 rpms. It is really bad when accelerating, but as soon as RPMs drop below 3000, the vibration goes away. It will do it in neutral/park as well, but not nearly as bad. I checked the flywheel/torque converter thru the inspection hole in the bellhousing and they are tight and there are no cracks in the flywheel. The vibration is strictly RPM related, not speed related at all.

I had HP Tuners hooked up to it and no major misfires (couple cylinders had 2-3 misfires idle, but 0 everywhere else) and 0 knock.

The engine did have extremely bad sludge when I bought it. It had low oil pressure and after taking the oil filter off, I could tell right away why. The oil filter was almost plugged and the oil that came out of it after I cut it open was almost like a caramel in consistency. I scraped out as much sludge as I could from the oil pan drain hole but I'm wondering if there could be sludge on the rotating assembly causing it to go off balance.

Any ideas on the vibration would be greatly appreciated!

Gadgetized

iTrader: (9)

So this vibration is present when the truck is sitting still at that RPM? Is the crank pulley wobbling at all? You might want to try and unbolt the torque converter and slide it back to see if the problem goes away.

teesee150

iTrader: (32)

I ran oil sludge cleaner and sea foamed the engine and it still vibrated. Dropped the oil pan and there is a film of sludge on the inside of the crank journals and all over the underside of the pistons. Any idea if that would be weight to throw the engine off balance?

The crank pulley does not wobble while the engine is running. I'll have to try and pull the torque converter back once I get the oil pan back on after cleaning the motor out.

teesee150

iTrader: (32)

I just wanted to post a followup.

Unbolted torque converter to eliminate the trans and it still vibrated. Ended up taking the crank pulley off and putting on a ASP pulley I had and the vibration was 100% gone so I'm ordering a new crank pulley and it should take care of it.