I’ve always wondered, I have the 2004 4.0l v6 automatic trans, if anyone has the same do you get a weird vibration at your feet around 2500 rpm? I noticed mine, in neutral/park, revs to 3k and when I’m driving it barely goes over 3.2k rpm. But anything over 2500 has a vibration. It recently went up to 4k rpm which is a first and the vibration got pretty bad and didn’t want to shift until the rpm lowered a couple hundred. Idk if it’s normal but if anyone else has it or had it I want to make sure nothing is wrong. I’ve only got 90k miles so I don’t want something bad to happen. (Also, I have the towing package so idk if that would have anything to do with rev limiter and shifting).

 

That's very low miles for an 18 year old truck, did it sit for a few years somewhere ?

 

Have you scanned OBD2 port for TroubleCodes, especially MisFire or FuelAir related?
Slim chance but, has 5r55e Tranny had an ATF+Filter change in the last 33kMiles?
Have the Plugs+Wires+CoilPack+OxygenSensors been changed in the last 100kMiles?

 

It only had 2 owners before me. The original owner drove it till 80k miles and the last only went to 83k miles.

 

It doesn’t have any misfire trouble codes or anything related to that. I’m not sure about the trans filter/atf change. I haven’t reached 100k yet but the thing runs very smooth.

 

Not any TroubleCodes?
Should be able to drive this engine+tranny at 5000+ rpms when needed accelerating & on grades, so somethings not right.
If still running originals, consider new Plugs+Wires, Clean+OhmCheck CoilPack.

Don't think its the source of the RPM+Vibration issue, but considering mileage & notorious 5r55e & unknown history,
best do a TrannyPan Drop+Drain, retorq ValveBody bolts, Band adjust, new Filter+PanGasket & top off with fresh MerconV.
Your profile lists "4x5"? If 4WD, best to also do
a MerconLV (not MerconV) change in the 1354 TransferCase, plus 75w140 in the RearDiff & 75w90 in the FrontDiff.
Push some fresh grease into the FrontBearingHubs thru the ABSSensor holes.

 

Thank you for the tips. 4x5 was a typo. Yes it’s 4wd. My rear diff has a very very small leak so at some point I’m going to get new gasket and refill the fluid. And will most likely do front while I’m at it. I don’t know why but I’ve only seen it go up to 4k rpm once at almost full throttle so I’m not sure what’s going on. The trans fluid is full still not terribly discolored or anything; can still see the original color but is a little bit darker. Bad thing is I don’t have a maintenance history or anything for it at all.

 

Check the fan clutch when engine is off, see if there is a wobble, can you move the fan blades forward and back and see the clutch move a bit on the shaft

I had a 4.0l that had similar vibration above 2,000 and it was a bad fan clutch



Just a heads up, when trans is in Park or Neutral, or speedometer is below 5MPH, the computer activates a REV Limiter so maximum RPM is 3,000, or so, not exact, this is a safety feature
Is your speedometer working?

Exhaust blockage limits RPMs and can/will cause a vibration because of slight misfires as exhaust pressure builds up, and of course it would be RPM related
You can test for that with vacuum gauge

Fuel flow will limit RPMs of course, but would expect Lean Codes as well, so Check Engine Light(CEL) would be on

 

I’ll check the fan and clutch. Yes my speedometer works. I know about the rev limiter but when driving it doesn’t really ever go over 3k. I just got a new exhaust, but only from the cats back. Could be the cats. I don’t have any CEL. Just a passenger airbag light but that doesn’t have anything to do with it, I know why it’s on.