I can feel it in the accelerator pedal and the engine seems louder, kind of boomy in the cab. It happens from 1800-ish RPMs to 2100-ish RPMs. Running 2300 down the highway it's as smooth as silk, no pedal vibration. It's RPM dependant, not speed. Could it be tired injectors that aren't evenly popped? I dunno, but it's annoying. Tell me what to check, fellas

 

only under acceleration? or always?

 

motor mounts?

 

Lack of Stack?

Maybe your fuel pressure is running low in that range?

 

I can feel the vibe in the pedal pretty much all the time (in that RPM range), but it really shines over 10psi

Quite possibe...

I'll just let that slide...this time

Ahh, more gauges They're coming.

 

Harmonic balancer slipping? They do go bad sometimes.

 

Could the exhaust pipe be hitting the frame?????

 

I've looked into the exhaust, but I'll have a closer look for witness marks. Thanks for the suggestions!

 

So we know its Directly tied to engine RPM.

Can you reproduce it with the clutch pushed in? or with the tranny in Neutral?

all of the clutch and 1/2 of the transmission always spin at engine speed when the clutch is out.

 

hmmmmmm..... i just may have the same symptoms as you...... I'll keep you posted if I find it..

 

Ahhh but I wont!! Its just got to be that muffler, im tellin ya, your motor is revolting against this horrible horrible censorship. LET IT SPEAK!!

Im going to jump onto the harmonic balancer band wagon. With 440K miles I cant immagine its still in tip top shape.
Check the T-case fluid lately?

 

Just to clarify.........when you say it is "RPM Dependant", do you mean it happens at that rpm in each gear, or just in top gear? If it is the latter, I would be more suspicious of something in the drive train, whereas if the former, more like possibly the harmonic balancer on the crank.

 

It'll do it in every gear. I notice it more in 5th because that's where I do most of my driving.