Interesting hum/rhythm/drone sound in 5th gear only

Whats going on - I have a 2016 Tacoma. Bought it with 35k, just turned 60k. I had an Icon 2.5" stage 5 installed after owning it for a few months. It has spent 20k plus on the suspension. No carrier drop was installed. Truck drove great. Nothing changed. Last week I started noticing a weird rhythm vibration drone. It does not vibrate my wheel, floor, or truck. It is more of a hum, hum, hum, hum every 1 second I feel like - sound only. It does it in 5th gear ONLY. Highway speeds the hum is much more noticeable, but at 40 chuggin in 5th I can hear it too. The ECGS bearing was done when I lifted my truck as well. I tried a carrier drop and it did nothing so I took it off. I am so lost. When I let off the gas, it stops immediately, as soon as I put on a load with the pedal, it starts immediately. If it shifts up to 4th, its smooth as can be, if it shifts down to 6th it is smooth as can be.

I am at a loss? I have been reading and searching and everything I see and read is not relevant to my exact problem. At this point I am looking for any ideas before I spend an assload chasing a problem with the dealer.

Thank you,
-G

 

Anyone? Seems to do it when my truck is warm. When I head to work in the morning and hit the highway briefly first thing I cannot replicate it. Coming home it always does it.

 

Gremlin.

 

I have a 21 off road manual transmission and I went for a longer drive yesterday and noticed mine was doing the exact same sound as yours when cruising on the highway in 5th gear. I shifted into 6th and the sound completely went away. No performance issues or anything, the truck was still driving great. I only have about 800 miles on the truck at this point.

 

My guess is it’s your rear driveshaft harmonics due to the mismatched u-joint angles from lifting. There are several threads on how to fix it with shims. However, I haven’t been successful in fixing the similar issue I have.

 

I tried doing the spacers and the shim work and couldn't get it either. I recently purchased a new icon leaf pack to upgrade my suspension for a different reason, and the truck is noticeably better now. I put option 3 in for towing on the leaf pack, but that raised my rear end a bit, in turn changing the angle. My other thought was maybe the axle wasn't completely straight behind the truck? Tranny was also flushed at the same time as well.

I still feel it from time to time, but significantly less. Down to about 3 variables here.

 

Same rpm’s and load in other gears and no issue?

 

Yup

 

You have tampered with the ride angles of the truck and now you must compensate for that by making adjustments on the undercarriage.

The fact you lifted it further and your sound got better is indicative that your carrier bearing is the issue here. You need to adjust the angle properly and if you can't do it you need to take it to someone who can.

If you ride on it like that for long enough then you will damage your carrier bearing prematurely and have to replace it in short order.

 

Honestly it could be anything. Could be as simple and harmless as the dust cover spinning at the diff. I wouldn’t worry about chasing random vibrations unless they are intolerable.