Vibration at 1500 rpm

[GaFJC]

I have a vibration at 1500 rpm that feels almost as if is "rotational" and harmonic. While I have a similar vibration at roughly 2500 rpm when the AC is on it is very subtle and not as pronounced as the lower rpm vibration.

The 1500 rpm vibration seems to happen at roughly 30 mph (AC off) and cruising on a straightaway. I don't notice it at all when accelerating or at other speeds or rpms.

The tbelt and water pump, plugs, CV boots/axles have been replaced in the last 2k or less. Same with tires and a fresh FEA. I've also cleaned the MAF and throttle body. Trans fluid has been replaced, so has transfer case fluid.

Could it be the harmonic balancer (would this have been replaced with the tbelt and water pump?) or possibly the bearing in the AC pump, alternator or power steering getting ready to crap out? None of the three are noisy.

It idles smoothly, accelerates well, MPG seems to be within range, and no other issues. 123K miles on the clock.

Sorry for all the details, just wanted to be thorough.

 

[marshotel]

Does the vibration occur at 1500 rpm if you put the transmission in neutral and rev the engine?

Or does it only happen when you are going 30 mph?

Maybe try checking the driveshafts for damage?
balance your tires?

 

[GaFJC]

Does the vibration occur at 1500 rpm if you put the transmission in neutral and rev the engine?
Or does it only happen when you are going 30 mph?

Maybe try checking the driveshafts for damage?
balance your tires?

Have only noticed while in drive and 30 to 35 mph and the approx 1500 rpms OR so.


I've lubed my driveshafts very recently and they appear to be fine? That said, I have tried to fill the rear slip yoke to a point where the old grease pushes out past the seal but it hasn't yet. Wonder if that could be contributing to the problem.


Tires and balAnce are only 2k old and no wheeling, only DD miles. Worth checking though

 

[OregonLC]

Similar...

https://forum.ih8mud.com/100-series-cruisers/507925-engine-vibration-resonance.html

 

[GaFJC]

Wish cleaning my TB and MAF solved the problem. I also suffer from OCD and won't be happy until I figure this one out. They'll be much hushing of the kids and no radio until this is resolved.

 

[OregonLC]

Is it at all speeds at the 1500 rpm or just at 30-35 mph and 1500 rpm?

 

[GaFJC]

Good question. I was probably premature saying its a certain mph, it's definitely in the 1500 rpm range though

 

[OregonLC]

Does it happen in N when stopped? If so, might be your fan being out of balance.

If you put it in N at whatever speed seems to be the worst does it persist or go away? If it persists it's drive train. If not it's on the engine side.

Have you checked all of your mounts - engine and trans?

 

[GaFJC]

Does it happen in N when stopped? If so, might be your fan being out of balance.

If you put it in N at whatever speed seems to be the worst does it persist or go away? If it persists it's drive train. If not it's on the engine side.

Have you checked all of your mounts - engine and trans?

I'll try putting it in N versus keeping it drive, a very good point.

I hope to have ACC here in Atlanta install my DT headers in the very near future and I'll ask them to look at the mounts. I've also read where the front diff mount could be a cause also.

 

[OregonLC]

IIRC, because of the IFS, the front diff is hard mounted to the frame. So I don't believe there's anything that could be going on there. If your vehicle is lifted, you could be getting NVH issues out of the CV's, but that would be at all RPM's and speeds and would be worse when turning.

I think you really need to isolate it to a engine vs drive train thing. If she's quiet in N then it's probably either a mount or engine harmonic. The 2UZ isn't bad but all vehicles have a natural harmonic frequency and if the engine vibrations hit that they will feel amplified. In my case, I believe it was a slightly rough running engine (maintenance issue) that resulted in my vibration. I still get a little bit of weirdness right when I come to a stop when the IAC allows the RPM to drop from 1000 down to 750, but at idle it's completely smooth.