Pulsating drone after lift. Go figure

[4runherpow]

So, as I deal with a separate issue with my LCAs I also have this new fun issue to solve...

After my 2.5” lift, at highway speeds I get a drone and a pulsating drone that is acceleration dependent. Goes away completely with foot off of the gas.

Here are the specifics:
- I feel a slight vibration in pedal and floorboard around 50mph and here a low hum drone that goes away with foot off gas. If I give it a bunch of gas vibration goes away and is smooth sailing as speed increases.
-At 70ish mph I again get a drone but now it is pulsating and again throttle dependent. Goes away after 82mph or so (might not pulse actually so less noticeable)

I’ve read that pinion angle can change which could create this. I also noticed that the noise will ebb and flow as I go over rolling bumps on the highway. Almost as if when the geometry changes the noise goes in and out. But again it is 100% acceleration dependent. If I take my foot off it goes away completely.

Does this sound more pinion angle related or like the front diff itself? If it’s the angle then how do I change this to bring the angle back to stock angles? My other thought was maybe engine mounts because the vibration feels less when rpms are not around 2k but instead in the higher ranges (smoothed no noise). But this theory may be stupid.

Thanks in advance for your theories

 

[jrm]

Just a thought..but it could be a change in the tires contact patch due to less camber due to the lift? Assuming you lifted the truck w/o UCAs and the tires are fairly worn..

 

[4runherpow]

Just a thought..but it could be a change in the tires contact patch due to less camber due to the lift? Assuming you lifted the truck w/o UCAs and the tires are fairly worn..

That is a good thought actually. But I think I figured it out.

I had to drive her a decent ways last night and I realized something... she doesn’t “sound” like my old 06’ rig I use to have. I realized that there is a drone (not engine noise) from exhaust. It sounds like it’s in the engine bay or directly under me. It comes on with minimal throttle and disappears based off of combination of rpm AND speed. So, when I’m half way on the gas (2.5-3.5k rpm range) the vibration and hum is gone. It pulses between 72-80mph and is just straight drone 40-55mph.

I also received a P0420 code today. So, I think there’s and exhaust leak. Which I would of thought of earlier but when I bought her I immeadiatley had a new cat back installed due to rust and rattles and the muffler guy said everything else looked ok. Now I’m thinking he didn’t REALLY look at anything else and just said that. Should of thought of this earlier but it’s been awhile since I’ve heard the engine note. So I needed to hear it a bunch to realize it wasn’t quite right.

Question is now is it the pre or post cat sensor. AND is there a hole/leak pre or post cat. Pre cat makes me annoyed. Hoping it’s the gasket that runs from the y-pipe to the center muffler. Do those go and create drones/CELs?

Thanks y’all. 4runners are fun to talk about lol