Grinding in 4-wheel drive

[hilton850]

Been lurking here for a while but this is my first thread. Recently my '94 explorer started making a growling/grinding noise when the 4 wheel drive is engaged. sounds like it's coming from under the truck...maybe front driveshaft area? I suppose it could also be somewhere in the front end but sounds like it's underneath, somewhat centered. I have already converted to manual hubs, new in April. It makes the noise whenever the hubs are locked in also. Already checked the U-joints, brake pads and rotors were also new in April, wheel bearings look OK, transfer case shifts like it should and 4x4 does work, just makes noise. Just to be clear, when I put the transfer case in 2wd and unlock the hubs there is NO noise.

Just wondering if anyone else has had this problem and any ideas on what may be causing it.

P.S. This board is an excellent source of information, I'd like to thank the moderators for their hard work and everyone who contributes information.

 

[DeRocha]

What kind of terrain are you driving on? Does the grinding start immediately after engaging 4x4 or does it take a while? Does the grinding noise feel/sound different when taking corners? You indicate the grinding exists when 4x4 if off, but the hubs are locked. Try locking just one hub, drive around, and then unlock it and repeat with the other hub (just trying to eliminate left/right drivetrain issues).

When were the U-joints last changed? They normally last 100K miles on-road, but less when driven off-road.

Based on the no noise issue when in 2x4 you can eliminate brake pads and wheel bearings as the problem.

Common areas of grinding noises:
Brake pads and rotors {noise would occur in both 2x4 and 4x4}
Wheel bearings {noise would occur in both 2x4 and 4x4}
HUBS
U-joints
Spindle/axle shaft bearings
Low diff fluid
low T-Case fluid

 

[MrShorty]

First thing I'd probably do would be to get under the truck (2H, hubs unlocked) with a stethoscope (maybe an assistant). Rotate the driveshaft/axleshafts and see if I can hear the grinding. Then hopefully pin down where it's coming from.

 

[hilton850]

I do a lot of off roading with the explorer...dirt trails/mud/stumps/logs etc. The grinding starts as soon as the front drivetrain starts turning (either the hubs are locked or transfer case put in 4wd or both) and stops when the front drivetrain stops turning (back in 2wd with hubs unlocked). Good idea to try one hub at a time. Not sure about when U-joints were changed...I haven't done any since I've had it but they're all tight. I suppose they could still make noise even though they're tight. The noise is fairly loud...makes me think of a driveshaft rubbing on a big rock. My first thought was a bearing. maybe a spindle bearing?? I may have a chance to tinker on it tomorrow. I'll know more then.

 

[DeRocha]

I do a lot of off roading with the explorer...dirt trails/mud/stumps/logs etc. The grinding starts as soon as the front drivetrain starts turning (either the hubs are locked or transfer case put in 4wd or both) and stops when the front drivetrain stops turning (back in 2wd with hubs unlocked). Good idea to try one hub at a time. Not sure about when U-joints were changed...I haven't done any since I've had it but they're all tight. I suppose they could still make noise even though they're tight. The noise is fairly loud...makes me think of a driveshaft rubbing on a big rock. My first thought was a bearing. maybe a spindle bearing?? I may have a chance to tinker on it tomorrow. I'll know more then.

The 1 hub locked at a time test will eliminate U-joints, and spindle bearings as the unlocked side will not be rotating. The U-joint seal will become brittle over time and allow the lube to escape and moisture to enter.. On the Rear drive shaft this present itself as a looser and looser U-joint as the needle bearings are constantly being worn. On the front drive shaft the looseness is often masked because of in-frequent 4x4 use. This can cause the needle bearings to become fused together and appear tight, but are a time bomb waiting to explode..

 

[hilton850]

that's a big 10-4 on the U-joints geting dry. That actually happened on an old GMC truck I have. That one sounded different....more of a squeaking noise that wasn't a constant noise...it'd squeak like twice per axleshaft revolution (the bad one was out at the knuckle). I finally figured that one out when I broke the u-joint while I was plowing snow. Found the rusty needles after the fact. I'll let everyone know what I find tomorrow. Thanks for all the responses!

 

[hilton850]

Today I tried locking one hub in at a time and heard no noise with either hub. The only time I heard anything was when I locked the transfer case into 4wd and made the front driveshaft spin. When I got done that test I unlocked both hubs and put the transfer case in 2wd so I could spin the front driveshaft by hand. I crawled underneath and the shaft spun easily but I think the bearing on the output of the transfer case might be going away...it felt a little rough on that end of the shaft...like there was a little sand in the bearing. Anyone have trouble with the bearings on these transfer cases?? This one has probably been abused a little more than most but from what I've heard they can take abuse much better than the transmission(mine is an automatic). If I can get to the parts store tonight I'm going to change the oil in the transfer case and the front and rear ends tomorrow. I have some other stuff I need to do to it for fall maintenance too.

 

[eXploring aussie]

Fantastic stuff guys !!!
Now some more places to looks investigate...
I have all similar noises but with auto 4X4.
First thing is to check fluids, I wouldn't expect it have been taken cars of at my regular services through the workshop ???
I'm sure it's more than that, so I'll definatly be back...

 

[hilton850]

I think I found the source of my front end noise. While I was changing out the fluid in the front diff, I found that there is a slight amount of play in the pinion. I vaguely remember the previous owner telling me that the front pinion seal had been replaced shortly before I bought it. I'm hoping the nut backed off a bit since I've been using the 4wd more than the previous owner. I'm sure the bearings are probably on their way out but I'm going to pull the driveshaft and tighten the nut a little to take the play out of the pinion and put the preload back on the bearings. Hopefully it will last through the winter and I'll plan on replacing pinion bearings and seal next spring.

 

[hilton850]

Well, in case anyone was wondering, I tried tightening the pinion a bit to take up the play in the pinion bearings. I went as far as a 3/4" IR impact with 110 psi going to it and no dice. I couldn't get the pinion nut to move. I guess it didn't back itself off if the 3/4" impact couldn't budge it so I guess new bearings are in order. It will probably be sometime after christmas before I get to it. Thanks again everyone for the suggestions on how to narrow it down.

 

[paulleon1965]

1991 Ford ranger 4.0 loud noise in 4 wheel drive

i have the same problem but sound got worse after I replaced the front driver side tire the truck pulls hard right

 

[hilton850]

Sounds like you may have a wheel bearing problem....or a sticky caliper with a worn out brake pad...

Just to keep everyone interested up to date, I think I've found a whole new center section to put in from a junk yard. I was sort of forced into running in 4 wheel drive for a while because of a couple bad snow storms here and I'm afraid I've worn a funny pattern in the gears due to the bearings being bad. Plus I think it'll be just as cheap to buy a used but good center section as it will be to put all new bearings in the center section that I have. Hope everyone had a merry christmas and a happy new year

 

[CobraSix]

I'm afraid I'm at the same point on my 91 Exploder.

I have the same symptoms...loud grinding/humming noise (not quite either noise, but a combo of both) that only happens when the front hubs are locked (I still have auto that will be replaced this spring). Doesn't matter if the 4wd is engaged in the transfer case or not. I check my fluid and it looked grey, so I'm afraid the gear is toast.

4wd works....just sounds like I'm driving an old UPS truck.

I hate the fact I love this truck...