quicksilvr

I did a quick search, but turned up mostly howling coming from the rear.

Truck is a '97 SR5 4runner, 3.4 auto, 4wd.

Anywhere above about 50mph, there is a noticeable "howl" coming from the front end. It sounds like it's coming from the center....it doesn't seem louder on one side or the other.

The CV boots are all good, everything looks great underneath. There is no clicking, popping or grinding at slow speed. The transfer case does seem a bit rough in and out of 4Hi. I actually used 4hi quite a bit driving on I-35 in southern Oklahoma last week....that road was a disaster. Fastest I ever went was like 40 mph. I didn't notice any difference whether in 2hi or 4hi....and since I never drove faster than about 40 in 4hi, I never really heard anything. But as soon as I got up to speed, it's definitely there.

When I let off the throttle, it changes pitch and tone slightly for a second, and then goes back to sounding the same way it would if I had the throttle open. Its not engine speed related. Only wheel speed related.

Thoughts? I was thinking t-case, front diff or cv's. Besides those, I don't really know what it could be.

J2F42C

Big hungry wolf in the engine bay......

May want to look at the fan clutch. How does it sound at startup? Can you move the fan by hand?

BTW, did you ever get those codes cleared from the other week?

quicksilvr

hahaha.

I don't hear it at startup, I'll check it out though. I'm about 98% sure it's something drivetrain related. Also, I can hear it very quietly at slow speeds. A normal person wouldn't notice it, but I can hear because i know what to listen for.


(Yes, I got the codes cleared on my friends '99. However, the P0505 is still coming on when it's really cold. Not even every day, but probably 60% of the time. It stays stored....but the CEL will go off later in the day after a couple more startups. So it's not a serious issue...but it bugs me, because the IAC "should" be fine. I know it tested good, and it's nice and clean.)

J2F42C

When is the last time you have looked at or changed the fluids in the front diff, t-case, A340? It really does not sound like the fan clutch but it would not hurt to see if you can manually turn it.

Maybe try coasting down a decline in N while the engine is not under load and see if you hear it. Just make sure there aren't many people around, the brakes work well, and snow is not on the ground.

JWaldz

iTrader: (1)

I'm having the same issue.. Sounds bout the same as your describing it. However, I've also noticed if I rev up my engine then let off (when im in drive) it will make it louder and then fade out. When I step on the gas it goes back to being loud again. The faster I go the louder it gets. Best way I can describe the sound is as if a hum from mud tires, except louder. This only happens in drive, It wont make the sound if i rev the truck up in neutral or park.

Another thing I have noticed is when I'm coming to a stop, a couple seconds before I completely stop (being off the throttle and on the brake) it makes the noise and whines down. Again, kinda like a mud tire humming when coming to a stop except coming from the front middle area and not from my tires. I've been baffled cus I know my cv's are pretty much brand new. My 4wheel works flawlessly in all gears.

I'm gonna give this a shot tomorrow leaving my neighborhood and see if I get that whining down sound when I come to a stop in Neutral. If it still does it then what would be a conclusion?

quicksilvr

I have no idea when they were changed last. I just purchased the rig. I'm cleaning it up, getting it mechanically sound, and selling it. All those fluids are on the "to-do" list...so hopefully it will be solved with some fresh fluid.


Yep, sounds identical. However, I didn't notice the whine down before stopping...at least not as noticeable as you say. It really does sound like bad tire hum. I actually thought it might be the tires, cause they only had 20psi in them at first. But then I aired them up....and it still did the same thing.

Let me know if you figure it out. I'm going to try to get all the fluids changed within the next 2-3 days, and then I'll drive it and see what I get.

aviator

might be the wheel bearings... does it feel like its pulling a little to one side when it howls?

quicksilvr

That's the stumper. It doesn't exhibit ANY bad wheel bearing tendencies. Tracks straight, sound doesn't change when you turn left or right, wheel is tight when doing the shake test, etc....

JWaldz

iTrader: (1)

I tried going down a small gradual hill in my neighborhood today and stuck it in N after I picked up some speed and when I came to a stop, sure enough.. I heard the same noise.

As far as it being a wheel bearing.. I wanna say I don't think it is. I just did my passenger cv here recently and driver bout 6 months ago with no problems. I checked the bearings and they were fine. I do however have small wobbling and bump steer, but that's prob from my spacers. Which isn't probably helping anything. I just got a new wheel and tire setup so the spacers are coming off tomorrow. I'll let you know what happens after that.

I've also developed a ticking sound. Best way I can describe it is like a exhaust leak sound or a plastic sack in the wind at high speeds (random, I know). I believe it is rotational noise because well, it sounds rotational. It does not make the noise when I rev the engine in N or P. The faster I go the faster the rotation ticking is and the slower I go is just vice versa. If I let off the acceleration it stops and the heavier I apply acceleration the faster it make the sound. I don't know if it is in relation to the howling noise. The noise also sounds like it's coming from the center of the front.

Thinking of taking it in to a shop or having a mechanic take a ride and have a listen with me driving it somewhere.

Swimmerboy2112

iTrader: (2)

What about your alternator? They tend to whine when they are getting old or in cold weather.

JWaldz

iTrader: (1)

wouldn't the alt. whine even if you revved the engine? It's more of a howl than it is a whine anyways, but it only appears when driving.

Swimmerboy2112

iTrader: (2)

My alternator makes noise only when i've let off the gas with the car in gear otherwise the engine & exhaust are too loud to hear it.

And without actually hearing the noise its hard to say what sounds like what although i wouldn't describe the alternator as a howl but to some it may be a howl.

Just an idea.

Lysmachia

As far as the ticking sound goes, could that be valve tap? Did the ticking noise start when the howling started?

brian2sun

Sounds like the tires, a wheel bearing, or the diff to me. I would change the fluid in the diff like J2F42C said and see if there are any big metal shaving or chunks. Have you jacked the front end up and spun the tires by hand? You might be able to hear something that way and better pinpoint it.

quicksilvr

I drained the t-case fluid yesterday, and although it looked pretty golden and clear, there were some noticeable flakes/chunks coming out in it.

I'm picking up 5 qts of Redline 75w90 tomorrow, and will drain and fill both diffs tomorrow night, along with refilling the t-case.


Also: I greased the driveshaft's today, and they needed it bad. All the u-joints took 3 pumps before they crackled, and the slip yokes both looked very dry. You can pump the slip yokes till the cows come home and not hear anything though, so I just put 8 pumps into both, and we'll see what she does when I get it back out on the road. I have my fingers crossed that with the Redline in the boxes, and new grease everywhere...maybe the howl will be gone.

quicksilvr

Sorry, missed the second half of your question. No, I have not spun the front tires, because it's sitting on ramps still. Thursday I need to have it road ready, because it's going in for new valve cover gaskets. (I just don't have the time for that job, and there is a local small shop that specializes in Toyotas...he's only charging me $200, I figured it's worth it)

After I get it back, and I can jack it up again, I'll spin and listen. That is, if the howl is still there. I hope it's not!

aviator

The ticking is almost certainly valves... I had that and I started putting in a can of Engine Restorer about once every 4 changes and no more ticking.... also got back some power and mpg...

JWaldz

iTrader: (1)

I took my truck in to a shop that I know the guys there pretty well. They took it for a drive. Said the howling was coming from the rear, most likely the rear diff. Said the fluids looked fine but nothing out of the ordinary. They can't diagnose it more without taking things apart. As for the ticking noise, it's clearly coming from up front and I still dunno what it is. They couldn't hear it either, even though I can, so I'm stumped!?

Aviator, is this the stuff you're talking about >> http://www.autobarn.net/ch00015.html?site=google_base

wormhole

I had a similar noise on my 4runner and it turned out to be the ac compressor/clutch apparentmly took a dump on me. At least that was the diagnostic from today. They left the belt off the compressor and the sound went away.

Something maybe too check into.

aviator

Yep that's the stuff... works really well... brings back some pep in a high mile engine and quiets things right down... going to put a can in when I do my oil in about 2 weeks (due now but no free time til then at best... lol)
just shake it really well before you put it in...
fwiw I run CT motomaster 10w30 full synthetic (Mobil1 10w30 in house brand packaging same stuff but half the price)