I didn't expect the vibration to go away as I would get a bit of the vibration while reving the engine in nuetral anyway. Regardless, I wanted the new drive shaft in. So now to hunt down the vibration.
I had discussed this before, and got a few opinions but the main one was the driveshaft. So now that is out of the picture, maybe I could figure this out a bit. I'm thinking motor mount(s), but not really sure.
Pretty much I get a vibration around 3,000-3,500RPM. Nothing before or after in the RPM range. It might be a bit wider range, but pretty much that. Here are a few facts...go at it detectives:
2000, 120K
Done in past year: Head gaskets, all gaskets, timing chain, water pump, plugs, wires, etc
All fluids new in last 2K: Diffs, Trans, Transfer, Oil, Coolant, etc
Seafoamed engine and induction recently
MPG is 14 with mixed driving and plenty of hills
Vibration happens in any gear at that RPM
Engine has a tick to it
So, any thoughts and things I could test or look for?

 

Have you checked the engine mounts? Look for cracks and damage in the rubber.

 

It is hard to tell really. They LOOK alright, but hard to tell. Are they a real pain in the butt to replace? If not, might just swap them out and see.

 

They are not so bad to change if you have lifting equipment, I'm not so sure about using jacks.
If you do replace them then remove the driver's side first, then remove and install the passenger side and finally install the driver's side. The driver's side is smaller and easier to get out, this gives you wiggle room to do the passenger side.

 

Check the tranny mounts as well.

 

Yep, will do. Sounds like a pain though. Do you really think it could be the mounts? Only in a specific RPM range? I figured it should be worst at initial acceleration if the mounts were bad. I still think it is a possibility though. I'm just wondering what inside the engine could be causing it too.
Also, it is nothing too bad and I could deal with it, but just wanted to take care of it should it be an issue!

 

Replace the Roto-Flex at the rear. you will be amazed. I know I was. and it was the last thing I would have looked for. and that only takes 10 minutes.

 

So what was it doing before you replaced? I don't much much at all about this. Any links?

 

If you are getting the vibration in neutral I have a hard time believing its the drivetrain. Any chance the motor was rebuilt? How is the compression on the cylinders? If you have a cylinder that is losing compression, or maybe a weak injector, it may cause a harmonic vibration that only shows up in certain ranges. Vibrations are tough as just about any spinning item can cause it.

 

SO THE vibrations I was getting were at speeds of 30-35 and then around 70. The vibration was subtle, if you were in the passenger seat more than likely you were unaware. But being the driver I could feel the soft shimmy, after I changed the rotoflex I was made aware just how much the shake was there at other speeds as well. Maybe it will not fix your problem especially if you are getting the shake/vibration in neutral. But in any case crawl underneath and have a look, if it is cracking or is soft to the touch( you can squish it between your fingers) then you might want to replace it anyway. Not expensive and like I said 10 minutes to change. If it works than great, if it does not then, well you have eliminated one more options while making your drive train a bit stronger.