Hi there, im trying to track down where exactly a clunk is coming from on a 2003 Explorer 4x4(auto, hi, low). My buddy brought it by my house yesterday and i cannot pin point it. If you put the truck in reverse, once you hit the gas, it clunks pretty loud. If you just put it in reverse, let off the brake, it will not do it until you hit the gas.

I got the explorer up in the air and crawled under it. I had my buddy switch from forward to reverse, and back again. Every time he let off the brake in forward or reverse, it would clunk. The reverse clunk was definitely louder.

It does the clunks in all settings, -auto,hi,low. No flashing dash lights. The dash lights do come on accordingly. One thing he pointed out was the Auto,HI,Low Buttons themselves are not backlit anymore. Not sure if that has anything to do with it?

I cannot narrow it down as the whole transfer case, front driveshaft and front diff, shake with the clunk. U joints dont seem to have play (prying with small prybar)

I then went ahead and unplugged the big wire connector at the transfer case and the clunk went away.

I have read thread after thread and found alot of clunks. I was hoping one of you may have experienced, or know what the cause might be.

Thanx a million - Adam

 

My 2004 Aviator with 86k miles on it wasn't making a clunk, but I decided to change out the u-joints anyway since I tow a camper with it during the spring, summer, and fall. There was no play in the u-joints, but they were pitted and rough once I got them out. I definitely didn't replace them too soon. I'm not saying this is the cause of his clunk, but if he has more than 86k miles on his u-joints, his may be in similar condition as mine were.

You'll also want to carefully inspect transmission and transfer case mounts to see if they are showing signs of being worn out. Another thing to suggest he do is drain the fluid from the transfer case and front and rear differentials, looking for any signs of abnormal wear. These are often neglected and only changed once there is an issue rather than to prevent issues. Transmission fluid and filter is generally less ignored, but often not changed regularly enough. Old transmission fluid could cause the harsh engagement as well.

There's a TSB for harsh reverse engagement, but I don't think it also covers forward engagement, due to issues with the valve body. That might be worth looking in to as well.

-Rod

 

First off thank you for responding.

Being that the clunks go away when the transfer case is unplugged, would that mean transmission and rear driveshaft would not be involved in problem?

 

That's probably the case, but I'm not clear what happens when unplugging the electrical connector at the transfer case. If it puts the transfer case in neutral, then it may not rule out the rear driveshaft. If it defaults to 2WD, then it would seem the issue is with the transfer case. I did help a co-worker diagnose a bad transfer case in his Explorer, but his was either a 1996 or 1997. I'm not sure if basically the same case was still in use in 2003. I do remember him mentioning a difference between one with an aluminum case and one with a magnesium case, and he had to be sure to get the correct one.

-Rod