Desert Camper

My 1988 Toyota 4wd pickup (22RE, 180K miles) has a very intermittent noise that is driving me crazy.

I posted a Youtube of the noise (please let me know if you have trouble listening) at

https://www.youtube.com/watch?v=L655...ature=youtu.be

The noise happens 10 seconds into the video. The noise happens very occasionally, but at its worst, it scares me like "don't drive, pull over and call a tow". It has two parts: a mild low grumbling/grating/grinding noise, that sometimes turns into a loud grinding noise. The louder sound reminds me of rotating splines not engaging, or stripped gear sounds, but I'm no expert. I think it's coming from underneath the drivers side front, can't be sure.

I can't bring the noise out in a test drive unless I drive for 50 miles or more, often longer. Its just not that frequent. So far, 100 miles will always do it.

It has only happened in 2wd high with the manual hubs unlocked. Not clear if it would happen in 4wd and/or with locked hubs - I haven't yet been able to put on enough 4wd miles to be sure. It almost always stops when I pull over, even after I just coast to a stop without using the brake pedal. Then, usually, not always, it's gone when I start going again.

The milder noise occasionally seems briefly triggered by a bump, or going over a cattle guard. But driving on rough roads won't cause it to happen. It can happen on highway, freeway, paved or dirt roads. I'm pretty sure it's a rotational noise, but it can happen at any speed 5-80 mph, continues when speeding up or slowing down or shifting between any gears.

Things I've checked:

Looked underneath for anything loose, cat muffler and tailpipe are OK, wiggled tires for wheel bearing play, visually inspected front brakes and backing plates, taken apart and examined driver's side Aisin hub, oil levels in diffs, T/C and tranny are OK.

A main clue is how infrequent it is, but how loud it is when it happens. I can drive the truck, but can't rely on it for long trips. I'm hoping someone can take a listen and know what the sound is. Any ideas?

OldBlueMidnight

If one or more of the spot welds holding the heat shield onto the cat breaks, the heat shield can make quite a racket vibrating. Usually happens in specific rpm ranges. Seems like that's a maybe for your sound.

akwheeler

I also vote for exhaust related, hence effected by temperature so you have to drive around for a while before it will happen.
Loose media in the catalytic converter can make quite a racket also. Check for loose brackets, cracks etc on the whole system, tapping with a rubber mallet will often help find exhaust rattles.

Desert Camper

Thanks for the quick replies! I would be glad to find out that the noise is just vibrating sheet metal.

It's not the catalytic converter. I convinced myself awhile back the cat was causing the noise, replaced it with a new MagnaFlow cat, figured the problem was solved, but Oops, the noise came back unchanged. The new cat has no attached heat shield. Also, the muffler and tail pipe are relatively new, and they and all their brackets seem rock solid.

The truck has three bolted on sheet metal heat shields, one above the muffler, one above the cat, and one above the front exhaust pipe that curls up a little bit around the floorboards. The 10mm screws are all tight -- I snugged them up today to make sure. I had tried to check for anything loose that could vibrate before, but I went out today with a rubber mallet (good idea!) and did a once-over. With the handle of the mallet I did manage to get a resonance or mild vibration by tapping in one certain place on the front heat shield, It was just the sheet metal vibrating a little, not hitting against anything. It didn't sound at all related to "the noise", though. Just too small of a vibration.

I still can't find anything under there broken or loose.

My best idea at the moment (only for lack of other guesses) is that one of the AISIN hubs is partially engaging when unlocked. That might account for the "spliney-slipping" sound. But could that happen on-again-off-again as I am driving along? Is that even a possible explanation, given the observations?

When I took the hub apart before, I was checking that the spring was OK and properly installed, which it was. I did notice that the grease was a bit thin and sticky-dry. I didn't have any grease, so I just put it back together. But now I'm thinking the next relatively easy thing to try would be to take it apart again and clean it up and re-grease it, and exercising it manually a bit more to see that it's working smoothly.

moto809

My 93 is experiencing a similar noise in the passenger front hub area. I've yet to figure it out as it is VERY intermittent, but absolutely horrible when it happens. I feel a vibration when it happens with mine as well. And I have the straight splined ADD hubs.

Paul22RE

Does the pitch of the sound change with the speed you're going?

akwheeler

A front hub can make similar noises if it's not fully disengaged. They can also be assembled incorrectly and do just that. But it is more likely that it would make noise right away, not after driving 50 miles.
It's worth a check though.

dbittle

Another thing that can make that kind of sound is if the speedometer head is going bad. I actually have it going on right now, but it is intermittent as you describe and occasionally so loud that it is hard to have a conversation. I thought it was something rubbing a tire, then I thought it was something in the hub, but it is the speedometer.

Killemall

Not sure if your truck is manual but that sounds reminds me of when my clutch throw-out bearing was about to eat it.

Desert Camper

Very good question and I'm not sure of the answer. I'll have to wait until I hear the noise again, then I'll speed up and slow down, and report back.

Desert Camper

Yes it is manual. Did the sound come and go, and was it unaffected by depressing the clutch pedal and shifting?

Desert Camper

I thought of that but ruled it out because I can never see the speedometer needle waver when the noise happens, like I saw when the speedometer went on another vehicle. But maybe that's not enough evidence to rule it out, I don't know.

Desert Camper

I need this part

Bent tabs on pawl
What's possibly making the noise: The tabs on the pawl in the driver's side AISIN hub were twisted so the pawl could not grip the hub dial cover (passenger side is fine). It could grip a little bit but then popped loose.

I tried bending the tabs straight but a tab broke off due to metal fatigue.

Now I need the pawl. After internet searching, I found the following options on Ebay:

Pawl, spring and clutch from 82 p/u for $34.50

Unbranded entire hub for $26 which is supposed to fit my 88 truck

Rockauto sells an AISIN FHT-018 hub (should be a match) for $105 including tax and shipping. There are no junk yards convenient to my area.

Any suggestions as to the best way to find a replacement pawl?

Desert Camper

The problem was the pawl. I should have noticed it the first time I took apart the hub, but I guess I was in too much of a hurry.

I test drove 100 miles with no clutch assembly in either hub - no noise.

I replaced the dial and clutch assembly on the driver's side, using parts from a hub I bought through Ebay. I cleaned and regreased the passenger side hub, using a new gasket from Yotamasters. Drove another 100 miles - no noise, and no noise since.

Here's another note for anyone finding this thread when trying to diagnose an intermittent noise:

An intermittent noise I had before, that sounded like going over a rumble strip, and took awhile to figure out, was the result of a broken leaf in the right rear spring set.

Many thanks to all who responded!

87-4runner

So weird that you posted this...
my 1987 sr5 turbo A340h staffed started doing the same thing last night and I tried to make it do it today.
It will only do it when it feels like it VERY random. Haven't had time to do much investigating yet, but I will find it

87-4runner

I recently changed out my nice Aisin hubs for some Mile Marker hubs I restored... they look cool but, I'm pretty sure the little needle bearings are binding, which is causing the grinding/ chirping noise I'm hearing. Haven't put the Aisin hubs back on yet to prove that theory but, I'll report the results when I do.
it makes total sense and I remember those freaking little buggers being an issue when I was putting them back together. If they are worn or IF I was missing one ( I don't think I was) they could be a real problem. Fortunately all it should destroy is the needle bearings and possibly the inside race of the MM locking hubs. No great loss there lol

87-4runner

It was the locking hubs on my rig that were chirping( Mile Markers) ... it was random and loud.
swapping hubs back to the Aisin and now it's all good. 👍👊

dodored

Had the same issue on my '87. The hubs were out of adjustment and not fully engaging.