I started noticing this vibration about a month ago. It was very minor but now it's becoming much more noticeable. The closest thing that I can compare it to is - when driving a manual - having it in too high a gear. For example, you're accelerating and you're in 3rd gear but you should be in 2nd still. There's that struggling vibration present in my van when under power. I can only feel/hear this when I'm pressing the gas and making power. As soon as I take my foot off the gas it stops. The transmission is a rebuilt and only has 28k on it. It shifts up and down flawlessly. No hunting, clean, consistent, clean shifting. This noise/vibration is more towards the front of the van.

Since the van now has 195k on it, I removed the driveshaft and had the u-joints (top-tier Spicer) and center bearing (GM OEM) replaced and had the driveshaft balanced. Everything was original. The shop said the old bearings were still in good shape and the center bearing was in good shape but starting to make noise. I have some trips coming up and just had it all replaced so I don't have to worry about it again. I re-installed the driveshaft and the vibration/noise is still there. At least the driveshaft is not part of the equation anymore.

Before someone suggests tires, it's not tires. I just got brand new tires installed and balanced. The vibration was there before the new tires. Also, this vibration only happens under power.

The transmission is still under warranty so I'm going to have it looked at, just trying to see what I can come up with besides transmission. Any ideas?

 

if it's coming from the front of the van, and it feels like lugging, then it's not driveline. Maybe you have a bad cylinder, a bad engine mount, ...

 

I can see bad engine mount perhaps, this crossed my mind. The engine itself purrs, I don't think it's a cylinder issue. When I say it's coming from the front, I mean more likely engine/transmission than rear axle.

 

There's so many possibilities ... cracked flexplate , loose TC bolt, botched tranny rebuild, ...

 

Update:

Just took the van to a transmission shop. This shop is very highly rated and has been for decades. They really know transmissions and I trust them. They do not believe it's the transmission or torque converter. They checked the rear axle and do not believe it's that either. I just had my u-joints and center bearing replaced (with very high quality parts) and had the driveshaft balanced so it's not that either. He said it could possibly be engine mounts but the engine doesn't torque much under load so bad mounts aren't glaringly obvious. I want to replace the mounts simply to eliminate them from this equation but that seems to be a big and/or expensive project. The transmission shop said the best option may just be to let it progress to the point where it becomes obvious instead of just throwing money at it. Not sure what I'm going to do at this point.

 

Have you had an alignment done lately?

 

Almost sounds like you are describing an engine misfire rather than drive line vibration. With a scanner you can look at misfire count and see if it goes up when you feel it. It might not be bad enough to set a code.

 

I will check this, it's a possibility. However, what I'm experiencing is an oscillating vibration - something spinning is involved. I can feel/hear a consistent sine wave. I've dealt with misfires/ignition breakdown before and this is different.

 

find a shop with a pico scope vibration analyzer. they can test drive and determine the frequency and order of the vibration. with this information it can be isolated to engine, trans, driveshaft, axles or tires.
another company has phone app to determine vibrations...if you want to buy it $300

 

if the noise is audible enough, you may even be able to use a free spectrum analyzer app to do what tech2 says.