I know this will be very hard to diagnose but I thought I’d ask any way…maybe somebody come across that in the past.

There is very annoying screeching (sounds like metal to metal) noise that I have under my 1996 4Runner (auto, 4x4, 3.4L, truck has 96 k on it). With windows down it appears to be coming from the middle of truck: right around transfer case or maybe trany. From the driver seat (windows up) it sounds like it is coming more from the right but the same general area.
Here is a kicker: I can only hear that noise when the outside temperature below 40 degrees and I am coasting above 25-30 miles per hour, if I apply even slight acceleration or speed drops below 25 miles an hour the noise goes away. Putting 4x4 “on” makes no difference
My first thought was drive shaft: U joints (even I serviced them regularly) so I greased all of them very well but the noise still there..
I just can’t understand what else it can be..??? I hope it is not a trany…???
Other than that truck in the perfect shape and drives great.
Thank you in advance.

 

U-Joints problems can be deceptive. For instance, my RX-7 slowly developed a noise which sounded exactly like pinging.. Happened only under acceleration. Thing is, Rx7's don't ping.

The clues that eventually led to the u-joint, were, when it got bad enough, was that it did not happen in reverse. That led me to check the u-joints, which indeed had slop in them.

Also, my '85 Toyota PU developed a slight metal-to-metal noise. I traced it to the front of the drive shaft. I had not noticed a zerk fitting there. After lubing the problem didn't go away immediately, but after several days. Of course I then added another round of lube. No problems since then.

Had another problem once, on the 4Runner. Sounded like a disk brake telling me it needed changing. Except it happened all the time, not just when applying brakes. And it was coming from the right rear drum. But once I was sure where it was coming from, I noticed differential oil dripping from the drum onto the tire. Replaced the seals and bearings, replaced the shoes. Problem fixed.

Not sure any of that helps, but just to give you an idea of my experience with noises in those related areas.

 

Rdharper,

Thank you for response and thank you for sharing your experiences. That is exactly what I am looking for so I can pint point the source of my “noise”.
I am hopping that it is one of the u-joints and nothing else.
I do not think I missed any zerk fittings, but I will see if I can lube it more.
Although, one thing for sure, the all undercarriage area around my u-joints will never rust, with all the grease I have there :-))

 

hehe, sure they do, once as a warning, and the second time, ka-pow... hello broken apex seal

 

i have they same thing going on but i think it sounds more like a heat shield to me

 

Thing is, this is not the place to argue this. But just for the record, I've had one Rx7, still have, still runs as well as the day I bought it. Been the cheapest most reliable vehicle I've *ever* owned. Oh, and it sill passes the infamous California SmogII with the lowest numbers of all my vehicles. And it has the original apex seals, thank you very much.

Only downside is, my wife hates it. So I have the Toyotas as well. I think the low to the ground skateboard cornering, and a ton of power just isn't her thing.

Then again, I love the Toyota's well.

 

hehe yeah i know they are great cars. the turbos however have issues when pushed to the limits.

 

Thanks for replays.
I will let you know if more lubing will do the trick, after outside temperature will drop below 40 degrees again and I can verify that noise is gone (hopefully).
I am in Fort Worth, Texas and it will be in lower 70’s for a whole week. :-))

 

Another way of getting a better idea, would be speed of the noise. Since the u-joints rotate what, 4 times for every wheel rotation you should listen for that as well. If it happens once ever wheel roatation it's not your driveshaft, it could be the rear axle bearing(s)....

If you can lift your truck "safely", you could get in there and play around. I narrowed my issue down to a passenger side rear axle bearing by tugging the e-brake with my hand and listening. You would also be able to hear exactly where the sound is coming from since everything in the rear of the truck sounds like it's from the middle while driving it.

 

Just want to let everyone know the noise that I had was gone in about a week of driving after I greased U-joints. So I guess it took that long for grease to get through all places in U-joints?
Thanks to all!

 

turned out my problem was just the intake...i guess the deckplate mod does work..haha

 

That fits with my experience. I'd go back and add another round as the delay suggests it was dry and would benefit from more lube.

Hopefully no damage was done... you might try to see if there is any play. If you can't move the key parts, you are probably in good shape.

Did you find a zerk you'd missed, or did you just add more lube. If you'd lubed all the fittings before, this suggests you are underlubing, probably being overcautious. As others have said, on parts that don't have rubber, it seems to be safe to put as much as it takes to visibly see the lube start to push out of the joint.

And by the way, thanks for finishing up this thread. Too many people don't... I think I'm guilty of this a few times myself.

 

Yep, I will do that.

No damage: there is no play at all.:-)))

I did not missed zerk, I just added more lube.

You are probably correct, because I had lubed before at least twice a year.


Thanks!