I have a 2009 jku rubicon with a 3” lift and 35s that I’ve had for about 10 years. For the last couple/few years I’ve had consistent vibrations in the seat mostly at 34-35, 42-44, and 47-49 mph under light acceleration. When I take my foot off the gas, it immediately stops. I don’t usually feel it under harder acceleration. I’ve removed my front driveshaft with no change. I just removed my rear driveshaft and tested in 4hi and still feel the vibrations but not as intense. The below is a bunch of maintenance I’ve done in the last couple months. Any suggestions on what I should try next? Any advice is much appreciated!

-New tires (35s) and balanced
​​​​​​-New Rancho geometry correction brackets
-New track bar
-New end links
-Replaced upper oil pan gasket
-Replaced all brake pads
-Replaced front brake hoses
-Flushed brake fluid
-Flushed power steering fluid
-Replaced all rotors
-Replaced front ball joints
-Replaced front wheel hubs & speed sensors
-Replaced drag link
-Replaced tie rod ends
-Replaced steering stabilizer
-Replaced front sway bar bushings
-Replaced front drive shaft Rzeppa CV Joint (the boot was torn)
-Replaced front axle seals
-Changed transfer case fluid
-Changed front and rear differential fluid
-Replaced all shocks
-Replaced all 5 TPMS sensors

 

You may wanna check your engine mounts. I wonder if they’re worn and causing the vibrations? The more common symptom of a bad motor mount is a thumping feel when stepping on and letting off the gas though.

Sometimes shocks can cause a harmonic vibe at certain speeds too. Does the vibration stay consistent regardless of roads/road conditions?

 

Thanks for the feedback. I’ll have to take a look at the mounts. It has 143k on it. I don’t feel any thumping. The shocks are new bilsteins. The vibration feels like rumble strips and is pretty consistent no matter the road conditions.

 

I'm thinking similar to sv_dude, but it instead of defective mounts it might be exhaust piping (or cats) that' are too close to the body/frame, or rubber exhaust hangers that are hard (or broken). The motor mounts are fairly soft by design so the engine rocks with torque changing the position of the exhaust -- The exhaust crossover and Y pipe are prime suspects.

As for motor mounts, an old trick to firm them up is to fill all or part of the hollow space with Windo-Weld (windshield adhesive). Did it years ago to my Jeep. It works well, makes the clutch feel a bit more precise. I filled one side of each mount without removing them using a caulking gun.

 

The mounts look good and the exhaust is new but the problem isn’t. I put the rear driveshaft back on and the vibration is more intense (like I expected). Any other thoughts? Could it be something in the rear end?

 

Is it the original rear drive shaft?

 

A friend of mine, after an accident, found he had damaged motor mounts, so replaced them. It did not fix the vibration problem. So, he changed the transmission mounts. Problem fixed.