I've got a 1998 4Runner and it's making a noise that I'm not really familiar with. When I depress the gas (pretty much at all) while driving, it generates a relatively subtle clicking sound. To my untrained ear, it sounds like its exhaust related, but I can't seem to recreate the sound while in park.

I'm hoping it's not transmission related, but when I stop there is often a little "thud" that comes immediately after the truck comes to a complete stop. The thud seems distinct from the little lurch associated with coming to a complete stop. I feel a little thud in the tranny sometimes when I accelerate from a stop in a somewhat less than gentle way.

Do either of these problems sound familiar? Do you think they're related?

Thanks for all of your help, guys.

 

The thud is probably the slip joint. Grease it real good to make it happy. If you have an exhaust leak, sometimes you can find it by idling the engine have a friend hold a rag over the tailpipe. Just dont burn yourself

 

So I'm mostly useless. Is greasing the slip joint something I can do myself? Do I need to have the truck jacked up, or is it easier than it sounds?

With the car idling, I put my hand over the tail pipe, it felt pretty tight and the engine reacted, but it didn't generate the sound that I seem to hear while driving.

 

There should be a zerk fitting on the driveshaft near the slip joint. With the rear suspension un-loaded(lifted from the frame), lube it with a grease gun until you see the joint push apart a little bit. If its been neglected, it may take a lot of grease. You can do it on the ground also, just need to use your best judgement as to how much to use.
Do you hear the noise if you rev it a little bit while in park, or only while driving? really tough to even know a general direction without actually hearing it myself. Could be exhaust leak, could be pinging, could be a rod knock, broken flex plate(assuming automatic), etc...

 

It seems to me that I can't hear the sound revving the engine in park, but I probably need to do some more tests.

It is an automatic transmission. Is a broken flex plate going to cause additional damage? How much do you suspect it costs to have that replaced?

I don't hear the sound while coasting in drive, only when I give it a little bit of gas.

 

A broken flex plate can cause the torque converter to crack as well. Don't know about cost, i would think $800-1000 or so. I think you would also hear that while stopped in gear so maybe not your issue. Maybe you were on the right track suspecting an exhaust leak. A rod knock should be noticeable while stopped and lightly revving the engine to 3k or so in neutral or park, so hopefully not your issue either

 

You know, the sound sometimes sounds like a bad CV joint and sometimes sounds a little more gutteral. It may just be in my head, but I think I might be starting to hear the little click while coasting now.

 

So the click seems to be getting worse, and it seems to go faster as I go faster, but it still goes away when I let off the gas, and it doesn't appear that I can recreate the noise in neutral or park. Could it be a bad U-joint or something else in the drive-train?

Any thoughts?

 

Some have suggested this could be a waterpump or the fake waterpump (fan bracket) going bad. The clicking your hearing could be the bearings in one of these failing.

 

Does the replacing the "fake water pump" involve as much labor as replacing the actual water pump?

Would a bad bearing in the fan bracket or water pump make the noise when revving the engine in park?

 

I hate to interject, but do not just fill the slip with grease. 1-2 pumps from a grease gun are more than enough. If its been a while, maybe 3-4. More than that can partially hydraulically lock it, making it unable to slip apart and press together to compensate for suspension movement, and ultimately damage the shaft.

Also, when exactly are you hearing the sound? You said that you can't recreate it parked, so what speeds are you hearing it at? Are you turning to the right or left? Does it happen all the time, engine warmed up or only when the engine is cold?

 

It's possible that the sound is somewhat lesser when the car is cold, but it comes back very quickly. I'm hearing the click at almost all speeds, whether the car is going straight or turning. The click goes away when I let off the gas (although I've noticed that its now making a couple clicks as I ease into a gentle stop). The clicking isn't noticeable at highway speeds, likely because the increased frequency of clicks has become something of a buzz that is inaudible over the road/engine noise. It is most noticeable at low speeds with gentle acceleration.

I moved a futon yesterday and drove across town with tailgate open a little bit, and the sound was, predictably, much more prominent.

 

That was going to be my next question, as in do you hear it more from the rear or front. As said above, check the ujoints. Jack the rear of the truck up, and move the joint up and down, and side to side. Any slop or play indicates a bad joint.

 

If I presume its the U-joint or something similar, any guesses as to how much its going to cost for me to repair? Any guesses as to how great my risk is for catastrophic failure?

 

Any chance your front brake rattle clips are missing or installed backwards? Those pads make a lot of noise if they aren't installed properly. Easy way to know is if the noise goes away when lightly applying the brakes.

 

A u joint is easy to do. Search for a write up here or on google. As for the failure possibility, it depends on how bad the joint is. Considering your not complaining of a vibration along with it, it still could be something else. One way or another, when you get under there to check them, grease them. If it goes away, you found it. If it doesn't, at least their grease now.

 

I recently had a similar clicking noise. It was very difficult to isolate and only seemed to occur under load. (no noise at all parked in idle) In the end, it turned out to be a noisy fuel injector. I used some injector cleaner/lubricator and it has virtually disappeared.

 

Update: The clicking got worse and I got busy so I took my car into the shop. They inspected the drive-line and found no damage. They gave the joints a good greasing and that seemed to cure the problem. It also fixed the vast majority of the transmission thunk at stop and start as one poster suggested. Hooray for lubricant! And thanks for all of the responses.