Ok, that almost imperceptable grinding sound has made its' self pretty prominant now. It definitely keeps cadence with the rpm and continues even after the clutch is disingaged. Before I described it as a grinding/scraping but since I have had a chance to listen again it is more of a metal to metal scraping/rattling. I am thinking distributor. Maybe starter, but I am not sure how yet. It seems worse when cold and clears after about 2500 rpm. If it is the distributer that might explain the choppy idle when at temp. The biggest problem I am having, of course, is when I get under neath it just decides to take a hiatus and wont make the noise . Figures. This makes it hard to pinpoint. The sound seems to come from nowhere and everywhere. I have, however, been able to narrow it down to the rear of the engine and when I can hear it, it sounds deep . Oh, and under load it will "click" (Something like a bad axle, but a little different). If anyone has an idea, I am willing to spend one more weekend trying to fix (Find) it. The fly wheel looks fine. I thought of the starter today, I will check it out tomorrow. The only way I can think of to check the distributor is to pull it. I have been avoiding that..... I guess procrastination time is over.

 

Manual 5 speed overdrive? if it is does the noise sound like rotating bucket half full of gravel?

If this is what you have then it is the input shaft bearing for the trans.

I had two of them fixed, if you bring Ford just the trans, they will replace the bearing for about 100 bucks.

 

"does the noise sound like rotating bucket half full of gravel?"


I love your description but... I don't know. Honestly it might a little but maybe more of a rattle. You know, like a fast rotating bucket with...7 rocks in it. When it happened to yours did it continue after 2500 rpm or so? Thanks for the advise on the tranny. $100 doesn't sound bad at all. I just need to pin point the noise. I was going to try again today but I had my 2 year old daughter who doesn't like sharing attention with the truck! I will let you know tomorrow....

 

Well it hard to say, trying to remember, this was a while back.

If the car is in neutral and idling it makes the noise, if you hold the clutch in with it in gear the noise is not heard because the input shaft is not spinning. (car not moving for both)

Try that and see if it "fits"

And yea the price from ford ain't bad, they will also look it over inside and make sure the rest of the trans is in good shape. One of the two I had fixed needed something else too, I don't recall what it was but it didn't add much to the cost at all, 20 bucks I think.

Don't bring them the car, just the trans!

 

Have you tried pulling the belts off and rotating pullies to find a potential bad accessory pully bearing? Our company truck had a horrible pulsating rumbling growl, turned out to be a water pump bearing! Any ball bearing can click if the retainer comes apart, in fact that is fairly common. Just a couple suggestions.

 

I think have the same problem on my 88 with an auto trans. It only happens when it is cold. After it warms up, or the rpm's increase, it stops. I sounds like a sort of muffled, metallic gargling noise.
If it is the input bearing, how bad can it get? Mine has been doing it for quite some time now. If I keep putting it off, what might happen?
Thanks!

 

BRONC-OH,

I had manual transmissions in all the broncos I had/have but one, I never had any trouble with that auto trans.


The manuals are the only ones I know of that the input shaft bearing goes out in and that’s only in the 5 speed OD behind the 2.9 V6 (86 and 88) models in my case. The manuals will last for thousands of miles after the very first signs of trouble, starts out with a very light grind and slowly gets louder as the miles rack up. Both of the two broncos were driven daily right up to the day I took them apart to fix’em.

I did have a car (not a bronco), that made a noise similar to what you state. I found the torque converter to flex plate nuts came lose. (auto trans). I tightened the nuts and the noise was gone. Its easy to check for and making sure all the hardware is tight is a good place to start when looking for the source of a noise anyway.

Dan

 

OK, after much head scratching, help from a friend and finally hearing the noise under the truck.... The cat! Well, both, actually, as it turns out.... $450 to get it fixed. Of all the stupid things.....

 

Are you sure the problem is with the actual cats? Mine rattled as well but it turned out that the two small welds that hold eachheat shield in place were corroded through and the shields rattled until the other weld broke as well. I just yanked them off when they worked loose. The cats are still in place so no emisions hang ups. Cheapest fix yet.