ASU4runner

Last night while driving home I noticed a rattling noise coming from underneath the center of the vehicle. I looked today and there were 2 pebbles stuck inside the catalytic converter shield. After these were removed, it still made the same noise.. esp. when I slightly tap the gas or when I'm pulling up to a stop light it's mostly heard between 10 and 30 mph in the 2000-3000 RPM range. It's almost too uniform of a noise to be a loose skid plate. The sound is like something metal is hitting while it is spinning. The u-joints could probably use a little grease but I don't see any signs of damage to them or the driveshaft. Has anyone else has heard this from their 3rd gen or know any possible fix for it??

blink

once in awhile my exhaust would fall off the rubber mounts and would produce a similiar sound that you are describing. I would just check to make sure that all the exhaust hangers are properly mounted. hope this helps

ASU4runner

All exhaust hangers are fine.. tapping around underneath, i heard the skid plate rattle slightly and the catalytic converter has another loose pebble in the shield. I'll try taking off the skid plate and removing the other pebble and see if that fixes it. Thanks!

Ranski

I have heard other people suggest checking all the heat shields under the body. They have a tendancy to work themselves loose.

I'm currently chaing down a rattle as well...still no luck...

ASU4runner

I decided to let it roll in neutral , then put it in drive and see if i noticed the noise go away. Well, it did. The noise is only heard when its in gear. This means it's got to be the driveline. Most likely bad u-joint ( I HOPE!!!). So i'm gonna get it to a shop to see if they can tell if i need a new u-joint. Thanks for the help guys.. even though I ended up figuring it out on my own.

Ranski

Make sure you report back on the diagnosis...

4rnr

dont be so sure on the driveline. I have had rattles that are dependent on the airflow through the exaust, which changes when you are in neutral. It ends up being pieces of my catalytic converter rattling in my cat or muffler. I drilled out my cat (and yes I still pass emissions) and whatever pieces i left in there break loose. Even if you didnt touch your cat maybe the PO did. Its worth a check. Just disconnect the cat at the back, and see if there is anything in there.

rimpainter.com

You guys would be very surprised the things you can diagnose using a rubber mallet. Take one under there and lightly tap various "sources" of the rattle; the exhaust, the skid plate, heat shields, etc.

It works really well. Give it a shot.

ASU4runner

Trusted tire place up the road determined it to be a bad u-joint on the front end of the rear driveshaft I went back there and saw/heard the exact source of the noise myself. My 4runner happens to have 2 u-joints right beside eachother just behind the transfer case to make a total of 3 u-joints for the rear drive shaft. Is this a normal setup or is this only with rear diff. lock options only? Just wondering b/c the dealership printed me out a diagram of the rear driveshaft based on my production date and he only could see one on the diagram when I have 2 on the front end of the rear driveshaft. Hmmm... I guess i'll try to figure out which one is bad out of the 2 and hope that it fixes the noise. It's definetly not anything outside of the driveshaft/u-joints.

As soon as I get the new u-joint(s) on i'll let ya know if this fixed the problem.

yotaluver

y don't you just replace um all they should not be that spendy and if 1 is bad they could probably all use it

ASU4runner

Yeah, I realized that and since i'm not sure which of the 2 is bad, i'm goin to replace them both (and the 3rd in the back as well). NAPA is $21 each, Toyota OEM $50/each.. I really hate unexpected expenses!!! :cry:

Jonathan

I think I have the same sound. I thought it was a heat shield rattle, but I've looked at them and there is no reason it should be that. I've checked everything and can't figure out what it is. Let me know if you find what it is and if it's really a bad u-joint. I have a 5speed and it even does it occasionally when i'm in neutral, but it seems to happen most when i'm accelerating.

ASU4runner

Just for kicks, I decided to pump some grease into the u-joints and what'dya know.. it took care of the noise!!! It's all fixed. Thanks again for the help.

Ranski

After reading the above, I said "that is exactly what mine does"

So when you said a little grease in the u-joint took care of it, I decided to crawl underneath and do the same.

Guess what I found...

Visit: https://www.yotatech.com/forums/show...601#post453601

Hyperlite

It sounds like the center bearing in the double cardan joint. It is a bearing that is between the 2 u-joints. It got one for $45 but I can't reasemble my driveshaft cause every u-joint I try is slightly too big for the double cardan. The napa u-joint fits the driveshaft diff side. Toyota told me it was not servicesable and they want $800+ for a new shaft. I will been driving around town in fwd till after the hollidays when I can find the u-joints.
I would suggest pressing the factory joints out and reusing them and buy a new center bearing.

My99

Just wanted to say thanks fellas! I was pulling my hair out all afternoon/night over this thing. I was like what happened to the toyota reliability I had last week!!?? I noticed last night as I was slowly driving through a neighborhood looking at christmas lights with my lady friend (who owns a JEEP!! ack!) that there was an odd ticking kind of noise coming from below. I didn't hear anything else of it until today. And it got seriously annoying. I had all the wheels off, inspecting brakes and hubs, looking for rattles anywhere underneath the truck. Finally I came in and ran a search. I saw where someone just greased up the U-Joints and all was well. I didn't suspect the U joints because I was having no issues as far as driveline slack. Well, a trip to Wal-Mart and 17 dollars later all the noises have stopped thanks to some grease-gun action. I'm sure glad, because I'm looking at putting a few thousand miles on her over these next few weeks including some snowy mountain traversing. I hadn't expected any breakdowns along the way either

dgold

Great advice. For the last week I've had a terrible buzzing / rattling / noise / vibration under my '99. Went under there with a rubber mallet and it only took 15 seconds of tapping around to see that the two heat sheilds around my front cat were loose. A bolt that sandwiches them around the cat had worked its way out or rusted off. It was all in plain sight, but I would have looked forever without the mallet - it helped a ton! Went to the local hardware store, dropped 15¢ on a bolt and nut and watta ya know... No more noise! I love quick fixes like that. Thanks for the great advice.

Some advice the hardware store owner gave me... I was going to buy a stainless bolt & nut, (I live near the harbor, so there's lots of stainless hardware around) but he suggested plain old steel. Once a little water and heat get together, the only way it's coming off, is if it's cut off. I had never before thought to equate a little rust with locktight. (please don't flame me for that - just something to consider)

[ For those searching yotatech trying to diagnose their noises, mine was a rattle / buzzing sound that I mostly heard while either under accelleration, or when I was in neutral if I really revved up the engine. The noise was worse when cold, and got a little bit better with drive time / heating up. ]