Front end whine/vibration at 25-30mph while in 4hi - no lift

I've read about well documented driveline vibrations that go away when switching from 2hi to 4hi. My noise is completely opposite... It's non-existent in 2hi and only happens in 4hi. I just noticed it this last weekend in our first significant snowfall of the year and I don't use 4hi much in summer.

While driving in 4hi there is a distinct howl in the front end at 25-30 mph and sometimes it's loud enough I'd call a vibration because I can occasionally feel it in the gas pedal. It happens at the same speed every time in 4hi, never happens in 2hi. It never happens at slower speeds and always goes away over 30mph. I don't recall it ever happening last winter which was my first with the truck.

The truck is a '15 DCLB with 32k miles and completely stock, no lift. I've changed the rear diff fluid but the front diff and transfer case fluid are still from the factory. I chose not to change them because I didn't use 4hi much and was planning on doing them in spring 2017.

Any ideas what this noise can be? Should I change the front diff and transfer case fluids ASAP? As I rapidly approach my warranty expiration I want to look into this now in case there's a chance I need to get it looked at by a dealership.

Thanks in advance!

 

Bump, same here 2014 sport 42k. Haven't changed Diff fluid yet.

 

How often do you go into 4wd? It's recommended that you go into 4wd every so often to lubricate the rotating assembly.

 

Honestly I go all summer without using it. Today was the first day I've engaged it since April, roughly.

 

That could be what caused the problem. I go into 4wd at least once a month for at least 3-6 miles to lube the rotating assembly for that purpose. Hopefully you won't need carrier/pinion bearings replaced.

 

How would I go about diagnosing that?

 

Diff fluids are supposed to be changed at 30k anyways, I’d start there and report back.

 

Yep, knocking it out this weekend. Only seems to be in the 4H 25-30 mph range then disappears.

 

Drain the fluid and check it for metal shavings out of the ordinary. The driver side cv shaft needle bearing could also be a cause but that's usually a problem on lifted tacos. I'd rule out wheel bearings because you would hear and feel the vibration in 2 and 4 hi but you mentioned you only feel it in 4wd. If your fluid has an abnormal amount of shavings in it then you may need to crack open that clamshell and inspect the bearings. Hopefully it wont come to that point.

 

As stated above, some amount of shavings is definitely normal so if it's questionable to you I'd post a pic and the experts here will give you a thumbs up / down.

 

Does the needle bearing vibration go away when you switch to 4HI? Thought I read that somehwere?

 

If it does go away in 4HI just about everyone here will recommend the ECGS bearing -- it's very common on lifted trucks for the stock bearing to cause the vibrations ... but the OP has the opposite problem.

 

It's usually a worn needle bearing that howls in 2WD and goes away in 4WD but I think what he's suggesting is the opposite here. In 4WD it's making noise because by not engaging 4WD the gear oil isn't being moved around inside the differential housing so parts aren't getting lubricated and are dry.

It's also important to engage the front to warm it up, the gear oil can get contaminated with condensation and the heat from stuff spinning tends to evaporate it.

 

Yeah it usually does since the diff activated is rotating but the OP said he hears it in 4wd and since he mentioned he doesnt use it that often it leads me to believe the issue is internal.

 

Another thing you might want to check is to make sure all of your diff mounts are tight.

 

That's how I'd start here - put a wrench on every bolt you can, change the gear oil in the front diff and transfer case, grease the front driveshaft (if it's got grease fittings on the u-joints).

 

The only time your sending power through the front driveshaft is when the truck is in 4x4 .
Have you been greasing the front drive shaft universal joints at every oil change . Have the balance weights fallen off the front driveshaft ? What are the chances there is a slight bend in the front driveshaft ?

Highly suggest going through my vibration thread to help you narrow things down
https://www.tacomaworld.com/threads/vibration-diagnostics-for-all-tacomas-write-up.520607/

 

I drive this mostly highway no rough conditions except snow in winter months. So I allowed diff to go further than recommended I'm sitting at 42k now doing the change this wknd. No bend in driveshaft, Toyota has been doing oil changes and greasing allegedly I never thought to verify seemed simple enough task.

 

And to re verify the hum is 25-30 mph then goes away above 30 in 4H, In 2H perfect silence.

 

Bruh...

I change mine like every other year.