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Clunk in 4WD and clunk in 2WD


September 5, 2010
Reaction score
City, State
Defiance, Ohio
Year, Model & Trim Level
1994 Explorer Sport
I have clunking going on everywhere. Its 2 different clunks though and I think they're completely unrelated. I'm new to 4WD, as this is my first 4WD vehicle.

I've seen people mention 4WD should not bind in gravel and I would think dry grass would be alright too although I'm not sure. I get tons of binding and clunking no matter what if I turn in 4WD at all. Obviously the more I turn the more clunking I get, but even if I turn slightly it'll usually go "clunk ... clunk ... clunk" I'm guessing its u-joints because the previous owner never used 4WD and its got 155k on it. I'm not sure though.

Also, when I'm in 2WD I get a loud clunk that sounds a lot like a binding clunk you'd get in 4wd when I hit a bump in front of a store or something. Can u-joints sound really nasty when not turning in 2wd? Sometimes the 2wd noise does get made while turning but it does happen when driving straight. I'm guessing radius arm bushings but I have no clue.

Thanks a lot guys.

when you're in 4w turning the most likely cause is the U-joints in the half shafts.

When in 2w, the parking lot bump thing, likely cause is radius arm bushings.

Also, you NEVER want to engage 4WD on high traction surfaces. A little 4WD primer for you:

When you engage 4WD, you're powering the front wheels through the transfer case / driveshaft / front differential and when you turn, the outside tire will turn faster than the inside tire. For example, if you make a right turn, the driver side tire is the "outside" tire and will rotate faster than the passenger tire which is the "inside" tire. The wheels rotating at different speeds cause driveline bind which needs to be released vis something slipping. On low traction surfaces (ice, mud, loose sand), the tires slip easily to release the excess energy of the driveline bind - that's what's supposed to happen.

On high traction surfaces the tires can't slip as easily so instead of releasing energy quickly, you let it build up. The bind cause cause the locking hubs, u-joints, axle shafts, or even the transfer case to break apart due to the build up energy.

Dry grass would be considered "high traction" and gravel can be hit or miss. If the gravel is hard packed, then you should refrain from engaging 4WD. If it's pretty loose, then you can use 4WD for testing purposes, but you probably wouldn't need it to actually drive.

Shaggy is right on - check the u-joints on the front axle shafts for excessive play. If they're loose, you'll need to replace them. The joints themselves are pretty cheap, but there is a fair amount of labor needed to pull the shafts out so you can replace them.

In regards to the radius arm bushings, you can find those by looking for a triangular piece of metal that connects the front axle to the frame. Easiest way to find it is to look directly behind the front tires and you'll see the actual radius arm. At the end of the arm opposite the axle, it goes through a bracket that is riveted/bolted to the frame. You should see a bushing at that bracket. If there is a huge gap around the rear of the bushing then it should also be replaced.