4.0 V6 making pulsating / imbalanced sound

Hello, I am a new member to this forum.

I've had a 2007 Access Cab Tacoma (4.0 V6 4x4, manual 6-speed transmission) for 3.5 years. Recently, I used my truck over the course of a month + to move to a new state, and unfortunately, this beat on my truck pretty hard as I had several heavy loads. One of my rear shocks broke, and also one of my rear leaf springs broke. Bummer ...

After having that all replaced, the truck rides smoothly and firmly again, but I've noticed another oddity ...

When on the highway between ~65mph and 80mph, and only while in 6th gear (approx 2,200-2,800 RPM), the engine makes a pulsating sound, as if something is off balance. This is not the sound of an imbalanced wheel, as when the engine is under load (steady state condition, or going up a hill) the pulsating sound is most prevalent, and while coasting or going down hill, the sound goes away. Odd thing is, around 75 mph, the sound seems to go away, and at other speeds w/i the mentioned range (65-80mph), the sound is not always present.

In looking around on some forums, similar complaints were the result of a bad U-joint or imbalanced drive shaft? In my case, it seems odd that this would only occur in 6th gear if that were the case. Could the transmission or clutch have a part to play in this?
It seemed that several people that had imbalanced drive shafts chose to not have it re-balanced for the cost and just deal with the pulsating noise. Does leaving the shaft imbalanced hurt anything?

Thanks for any thoughts and help anyone can offer!

 

I am having a similar issue on a 2013. I recently had the TSB done for the driveline issue. My problems are happening at about 30mph to about 50. And it sounds to be the same. It is a dronning or harmonic sound that pulsates until it gets faster and faster and goes away. I had it at my dealer and they said they could not recreate the issue. I am scheduled again on Wednesday to go on a drive with them. I will let you know what they have to say. To me it sounds like a drive shaft out of balance or U-joints sounding weird but really hard to say.

 

Thanks for the reply. Let me know what they say. I figure that is the best way to get it resolved if it needs to be ... call Toyota and have the mechanic go for a drive with me so he can hear it and isolate the issue.

 

This is somewhat unrelated, but may be how my truck's imbalance/pulsating sound started. I did not know this about Tacomas. Good to know ...
http://www.tacomahq.com/508/toyota-tacoma-leaf-springs-break/

 

So I got to the dealer this morning to go on a ride with the service manager and tech. Sure enough the sound was not there. I had to go on a 50 mile trip during the day and it started up towards the end of the hot day. I guess I will have to just drive in again in the next couple of days while it is happening for them to diagnose.

 

For your problem I would (on a flat straight peice of road) throw your truck in 4x4 when the sounds starts. If it goes away in 4wd you have the common driver side needle bearing issue. I had it with my 2012 after levelling it. I put the ECGS bearing replacement In the diff and my vibes went away 100%.

 

I'll try the 4x4 test and post my findings.

With that being said, I had both of my rear shocks replaced, and both of my rear leaf springs replaced (with heavier duty springs vs stock). I waited until this repair was done to make sure that my broken springs and shocks were not the source of the noise. They were not ... truck rides great now, but the noise is still there.

I went on a ride with a Toyota technician yesterday morn. I went out on the highway, and after hitting 6th gear, drove about 65-70 mph to get the pulsating noise going. He could not hear it from the passenger seat. I had him drive on the way back, and while he could hear the noise from the driver's side, he said it was subtle, and that a slight imbalance in my rear tires was more noticeable to him. He said he thought it was just from "power transfer" at higher gears, but that everything felt normal to him, and he didn't really know where to start chasing the noise.

I agree with the technician that the pulsating is subtle in nature, and mainly wanted to know if there was something I was ignoring that could turn into a bigger issue later. He said to just bring the truck back if the noise gets worse.

I'll have to look into the needle bearing more though.