1998 Explorer "Thump" Noise While Driving Up Hills

I have a 1998 Ford Explorer 4.0L that is making a "thumping" noise while driving when you hit any kind of incline in the road. I just replaced the u-joints so I know the noise is not coming from them. Could this be a transfer case issue? Has anyone experienced this same kind of noise? When you go up a hill of any size it goes "thunk" and sometimes does it multiples times but stops on flat ground or when going down hill. It doesn't make this noise all of the time.and there isnt any slipping like a tranny slip no power issues almost sounds like something is trying to engage and dosent all the way or something any ideas

Make sure the spare tire is secure and that the jack in the rear compartment is not moving around. Check the simple stuff first like for cans of stuff rolling around under the front seats, coils in the center console, items in the glove box, etc.

-Rod

Make sure the spare tire is secure and that the jack in the rear compartment is not moving around. Check the simple stuff first like for cans of stuff rolling around under the front seats, coils in the center console, items in the glove box, etc.

-Rod no its nothing like that it kinda sounds like someone is hitting underneath with a hammer . my first thought besides u joint was maybe the 4 wheel drive moter was trying to engage and then unengaged right away and made a thump but not sure if that is possiable or not its comming someplace from the transfer case or mabe even infront of that .

Make sure you don't have a broken anti-sway bar end link or a broken torsion bar/spring. The torsion bars are attached just under the front seats, near the transfer case.

-Rod

Make sure you don't have a broken anti-sway bar end link or a broken torsion bar/spring. The torsion bars are attached just under the front seats, near the transfer case.

-Rod ok ill check that out cause thats the area its comming from you can feel it in your feet when it slams thanks for the info

ok ill check that out cause thats the area its comming from you can feel it in your feet when it slams thanks for the info nope not that quess ill take it to a tranny shop and see if its the transfer case going bad

Did you find the source of the thump? I get a thump in my '99 Ranger when trying to accelerate or go up hills, but, it is the heater control flap slamming, presumably from a vacuum leak. I have not been able to find the leak though.

I have a 2001 Explorer Sport 4X4 4.0 I have this same type of issue where if im coming off of a easement / driveway i hear/ feel a Thump coming from the rear. Seems to me like was a rear sway bar link cluncking, but i can't find and obvious wear or movement. Anyone solved their mystery, Maybe can kick me in the right direction?

Mine was doing something similar. On mine, the plastic gas tank shield slid over and rubed on a U-joint making a terible thumping noise, usually in left turns.

I also hear a thumping noise in a 2002 Explorer. My brother bought a very clean 2002 with leather seats and a lot of options. It has the 4.6L V8, it runs great, rides very smooth, handles great, and so we were wondering why someone got rid of it? The answer is probably the noise he found when going up hills. Here in Pittsburgh, we have plenty of hills. When going up a hill, on a straight hill, so turning can't be a factor, it sounds like there is a big hunk of rubber fastened to the drive shaft and you hear a loud thunk everytime it rotates, as though it was hitting the frame or something else solid. As you know this kind of thing is hard to describe. It must be something common to 4 wheel drive Explorers. As it has been mentioned in this thread, there is no noise when traveling on the level, and there is no noise when making turns. The steering feels fine, his Explorer handles great on the level, it accelerates great, except that the fuel gauge mimicks the speedometer in reverse! We haven't had a lot of time to investigate this problem because of other projects but it sounds as though something serious could develop. Transfer cases is one item I have no experience with, but I suspect it could be something in the transfer case also. The first thing I want to do is see if a manual on Explorers will help shed some light on this problem. I just heard this noise myself this week. Now that I have heard it, I think I will ask a mechanic we have in this area. He rebuilt an Astro transmission for us, he did it right, when he gives a transmission back, you put it in and it will work with no nonsense. I just thought about him so I will ask him. I haven't even had a chance to look at the underside of this Explorer, but now that I heard it, I am getting real curious. The noise is pretty loud and hard to ignore.

This is a reply and we think the answer, that we can't explain for the loud thumping noise on the 2002 Explorer I used as an example. My brother did buy a warranty when he bought the car. He was goinjg to see if the warranty would cover the problem. The shop owner and mechanic found that there was 3 different brands of tires on the vehicle. The tires were all in good condition. The mechanic said that is the first thing the warranty rep would use to refuse service. The tires on the front were Dakota brand and the tires on the rear were a Firestone and a BF Goodrich, both of which looked fine, even after removing them and inspecting them. To get to the point, two more Dakotas were installed on the rear before calling the warranty company, but the thumping noise is gone, so the call for warranty service was not made. Its been a few weeks and the thumping has not returned. Is this a tire design incompatibility problem or what? Has anyone run into this before?

Were all three tires the same size and inflated to the same pressure? That's an interesting find, and something to add to the memory bank.... Thank you for the followup.

-Rod

Yes, the tires were the same size, the inflation pressure was the same, and the style of the tread was even fairly close. All of the tires had about 80% or their tread left also. My brother bought this 02 Explorer from a used car dealer because it was so clean for an 02 in this area. We have no idea how this mix up of tires got on there. Either the dealer or the owner put them on. As an added point, the Explorer came from a Ford dealership to the used car dealer, so who knows maybe the owner put the tires on, discovered the thumping, had no idea if the vehicle was ready to self distruct and traded it in. Then maybe the dealership didn't want to waste time on an 02 and just got rrid of it. It is a strange story, but now my brother loves it, the paint is in great shape, and the leather interior is beautiful. We don't have an answer, but someone knows about this, because the mechanic knew the warranty company would pick up on it.

Had a similar issue with my '97 Explorer. Bought new tires for the front but left the old ones on the back and the noise started. Thought it was a transfer case problem and took it back to my tire shop. They worked for hours and finally discovered that by putting two new tires (exactly like the front) on the truck the noise disappeared. They explained that it was something in the "on-demand" 4 wheel drive that caused the problem. Have had no other problems since the change.

Thanks for the reply Grundelwalken, its interesting that this sort of thing has been happening for a long time. It makes sense that it is because of the 4 whel drive. My brothyers 2002 is an AWD version. It is always in 4 wheel drive, (and thas probably why it is not the best on gas milage). If it was possible to drive his 2002 in 2 wheel drive, then we could have learned that the thumping had to do with the 4 wheel drive system. Its been amonh now and there is no more thumping. It definitely was the tire misatching.