Intermittent drive train noise 2017 XLT 4x4
 

2017 XLT 4wd supercrew, 3.4 EB, 10 speed transmission, newly bought end of May -- I'm experiencing occasional episodes of a low pitched gear-like noise that sounds like something's in a lower gear and winding up faster at relatively lower speeds up to 40 mph or so, and feeling like I should not try to wind it up any or much further, yet the 10 speed transmission seems to shift normally and is in 8th gear at 40 mph, and I can accelerate fairly normally while this extra noise thing is happening. This has happened about 4 times now in the last 2 months, starting about a month after I got the truck, and I have about 4600 miles on it now. Just had its first service at the dealer last week. The first 3 times, I could make it stop by stopping and starting the truck, and one time I engaged the 4wd high and then took it back out and it stopped when I did that.

Today, it did it again. I couldn't get it to stop even when putting in and out of 4wd, although the noise went away while it was in 4wd, but resumed when I took it back out. After stopping, turning the truck off, and restarting 3 times, it finally stopped making the noise and truck operated normally again, just like after the first 3 episodes. The noise kind of reminds me of being in 4wd low with an older model truck I used to have. And the way the noise sounds faster and faster as I increase speed up to 40 mph makes me wonder if it's some weird thing happening in the 4wd system? There's no way for it to be a rear end gear box issue is there? Anyone hear of, or experience, this before?

Bump. Thanks for any insights.

It could be the IWEs. They use vacuum pressure to retract in 2WD and engage when in 4WD or when there is no vacuum. So when you are in 2WD and turn off the truck, they engage. Start the engine and they retract (assuming still in 2WD). You could have a "sticky" IWE that isn't fully retracting every time. This would explain why cycling the engine could make a difference as this also cycles the IWEs to engage and retract.

Thanks. Sure sounds like a possibility, will ask the service guys at the dealer about it.

bump (hope it's OK to bump? am new, let me know if this is a problem)
Thanks

Bringing this up top again as I've continued to have this issue intermittently. I've kept records of every occurrence for a number of months now. It was happening unpredictably, maybe once or twice a week, and then not at all for several weeks. Whenever this gear noise issue occurs, I can make it stop by stopping the truck, shifting in and back out of reverse, then driving on. This has worked every time.

Because it was occurring unpredictably, it was virtually impossible to get it in to the dealer when the noise was occurring. I was able to show the dealer service rep one time that the noise could be reproduced by shifting into 4WD high, then driving for a few yards, then shifting back to 2wd, and the noise did occur that one time. So I left the truck there for a few days while I was on travel, and told them about the hub actuators possibly being part of the problem. When I got it back, they had not been able to reproduce the noise (of course) and concluded that I should stop driving on dry pavement in 4WD!!? I only did that in order to show them what the noise sounded like, but in all other cases, the noise has occurred when starting out in 2wd, again, unpredictably.

Here lately, it has started to occur after I've started out on the road and after driving for about 5 minutes, occurring about 4 times in about a week. Before, it would only happen when pulling out from a cold start first thing in the morning, or after work and sitting in the parking lot all day. I can still stop, shift in and out of reverse, and make it stop every time, however.

Has anyone else has heard of this happening? I plan to go back to the dealer at some point, but am expecting they will just say they can't do anything unless they can verify the noise is occurring (and presumably not just when using 4wd on dry pavement . . .).

Please clear this up for an olde guy.
Noise occurs when accelerating, either lightly or more aggressive?
When noise occurs, does shifting into 4H makes it stop?
Noise sounds like gear grinding coming from either the left or right front wheel area?
Noise disappears when off throttle?
Try those things, and get back here.
You don't need to stop and restart to do those troubleshooting things.

Doesn't matter the surface you're driving on, as long as you're not turning you won't hurt anything in 4X4 for a few seconds.

Let's all hope this is another $10 check valve fix.

OP: What has the weather temperature been where you live since this started? Sub-freezing temps seem to make these bad check valves leak.

Might be. That's why I'm asking what I did.:D

Thanks, johnday. I had a big long response written and somehow lost the whole thing . . . Anyway, here are some answers:

When the noise occurs, it's just when driving normally, usually after starting up, and more recently about 5 minutes after a cold start during normal driving. Not sure if it starts during minor acceleration, but I do know it does not manifest during aggressive acceleration. It's hard to hear until speed gets up to above 20 mph, and is a bit louder and spun up to a noticeably greater frequency (not higher pitched, just sounds faster) up around 40-45 mph. So, does not appear to be related to periods of acceleration.

It does not sound like grinding, but sounds more like "growling", I guess. Does not seem to come from one side or the other, seems to be in the middle somewhere. My wife doesn't notice it, and the service rep guy had trouble hearing it when I was able to get it to do it after going in and out of 4H the one time I was able to show it to them, but he did acknowledge it and said it was out of the ordinary. So, it's not obnoxiously "loud", nor does it sound like something's getting torn up (hopefully a good thing . . .).

Shifting in and out of 4wd high while “on the fly” has caused the noise to stop on several occasions. I did this a few days ago after we had snow and so had snow covered/packed streets to do this on.

On or off throttle does not affect noise. Only speed. Seems unrelated to the transmission as the transmission seems to shift normally, goes all the way into 8th gear up at 40 – 45, and the noise just keeps on when it is occurring. Again, this happens unpredictably and only periodically, although the past 3 days it has happened once each day. Today, it happened in about 2 minutes after I started the truck and was headed up the street, and I stopped at a stop sign, shifted in and out of reverse and it stopped, as usual. I pulled a travel trailer today for about 20 miles and it never occurred again.

Regarding temps, this started happening in the summer, and I first went to the dealer about it in August, so it does not seem to be related to colder temperatures.

Thanks for any help in figuring things out with this. A $10 check valve fix would be wonderful, doubt my luck will allow for something that simple.