Howl noise in 4WD

DGREGORY70

MEMBER
2013 FORD F-150
5.0L
V8
4WD
AUTOMATIC
72,000 MILES

I don't drive my truck in 4 wd very often at all. I switched it into 4wd on the way home from work this evening as I understood this should be done every so often to keep the solenoids and things operating. It was on a straight road and when I changed it over it started to make a loud, strange noise that I can't describe very well, maybe a howl, maybe gears. I then turned it back to 2wd and the dash said it was changed but it was still making the noise until I made a turn. I did this twice more on the way home with the same results. Once home I crawled underneath to see if there was anything to see. Vacuum lines were in place and nothing else seemed out of the ordinary. I took it for another drive with the same results, but this time I left it in 4wd for awhile longer to see if it worked it self out. It then made two very loud thumps that felt as if they were coming from directly beneath me. I changed it back to 2wd and once the noise started it seems fine again.

7 Replies

STEVE W.

MECHANIC
13,577 POSTS

Welcome to 2CarPros. While it is a good idea to exercise the 4WD from time to time, Never do it on a high traction surface like pavement or concrete. Only on loose gravel or dirt or wet grass where the torque doesn't bind the system. That was one of the causes for the excess noise and why it wouldn't switch out of 4WD. It is called Torque Wrap. It can do serious damage. As you don't use 4WD much the various U-Joints and CV joints should be checked for wear or damage to the boots and bearings. To see if there is something to be very concerned about go find a gravel road or similar lower traction surface and drive it around some in 4WD. It will make a bit more noise but shouldn't make thumps or other loud noises. Then you could put it on ramps or a lift and physically check the shafts and joints.

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Thursday, October 17th, 2019 AT 5:37 PM

DGREGORY70

MEMBER
46 POSTS

Okay, that makes me feel a little better I guess. Even though I've had trucks most of my life this is my first 4 wheel drive. I always felt conflicted about trying to exercise the system so to speak while also not using it on dry surfaces. I was told by friends that if driving in a straight line it shouldn't be an issue even on dry surfaces. So I've done that in the past and this was the first time it ever made that noise. I was afraid it was the vacuum hubs not releasing or failing, but it was weird because it sounded like the noise was coming from the rear not the front. Anyway, what should I be looking for or how can I check the shafts and joints as you recommended?

Thanks

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Thursday, October 17th, 2019 AT 6:05 PM

STEVE W.

MECHANIC
13,577 POSTS

With the transmission in park you grab the drive shafts and try twisting them and moving them up and down. You want zero play in any of the joints. So if you can move the rear driveshaft 1/8 in those directions the joint is bad. Also look at the areas where the bearing caps are for and rust or leaking grease. That is also a bad sign.
https://www.2carpros.com/articles/how-u-joints-work

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Thursday, October 17th, 2019 AT 8:54 PM

DGREGORY70

MEMBER
46 POSTS

So I was not able to get on gravel or anything similar today as I'm in a fairly suburban area, but I'll see if I can find somewhere this weekend. I did however crawl under the truck and with it in park and 2wd I can't move the driveshaft in any direction and the front axles seem okay, but the front shaft from the transfer case to the I guess front differential will rotate slightly, say from 12 o'clock to 1 o'clock maybe. It's solid up and down and front to back though. So is that an issue then?

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Friday, October 18th, 2019 AT 12:19 PM

STEVE W.

MECHANIC
13,577 POSTS

That motion shouldn't be an issue as it likely is the total amount of backlash in the gearing. With the vehicle in 2WD the front axle is unlocked. That lets all of the internal parts move until all of the slop to be taken up. In your case that means the small amount of motion from the transfer case chain, the front gearing and the differential all adds up to the motion you have. That backlash is something you need to have in the system to allow all the parts to move under load.
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