Can anybody tell me what this noise is?

[Fixnstuff]

It sounds like something thwacking against the bottom of my bus.

Some of the comments have given good suggestions and advice but that is A LOT of stuff to try to remember and check.

1) As loud as that noise is, the problem is likely to be very obvious upon a visual 'hands on' inspection by someone who knows what they are looking at. (Hands on meaning that they are going to have to grab on to some components and forcefully try to move them by hand to find something that is loose and shouldn't be) and that could lead them directly to the problem..
In any case it should be quite obvious and should not take much time to locate it- just a routine inspection to find where the noise is coming from.

I really should stop at that so you don't get more confused, but actually you are learning a lot so I'll throw in a few more cents worth.
Transmission mount(s)/Engine mounts. As with some of the other parts you've seen, they are metal and rubber.
The rubber acts as a flexible cushion between the metal parts which allows for some movement when under use as he vehicle is being driven. The rubber can be considered as a vibration dampener as well and it serves that function in the motor/transmission mounts AND the easiest place to see this is in the carrier bearing which is approximately in he center of the drive shaft assembly between the transmission and rear differential (the 'pumpkin' shaped thing in the middle of the rear axle which contains the differential gears (ring gear and pinion gear) which produce the rear end gear ratio between the drive shaft and rear drive wheel(s) It is a set ratio but those internal gears can be changed from a lower gear ratio to a higher gear ratio. Low gear ratio is for pulling power such as in a construction pickup that needs to haul heavy equipment on a trailer (like a bull dozer or end loader) to a to a construction site. Low gear ratio will run higher engine RPM for a given speed (also depending upon the transmission) so they are not very fuel efficient at highway speeds. HIGH gear rations are for vehicles that don't need that low end low speed pulling power and at highway speed they run less engine RPM and are more fuel efficient.
A common LOW gear ratio in these vehicles is 4:10 and a common high gear ratio is 3:55. You'll see people mention those particular gear ratios in various topics.

I like to teach but I'll stop there. Some people don't like long posts which is a difficult to break habit with me.

AN ALIGNMENT SHOP COULD MOST LIKELY IDENTIFY THIS PROBLEM DURING A FREE PRE-ALLIGNMENT INSPECTION. I use Les Schwab Tire company because there are only a couple of choices in this little town. They have excellent equipment, really good warranties on the work they do and some free services like free tire rotations.... BUT THERE IS SOME OTHER ADVICE THAT YOU NEED TO KNOW and I'll give you that advice in a reply to david85 after I post this and make some coffee. and a couple of other quick chores (start a load of laundry and I forgot what else)


2) The noise is muffled in your video, it's muffled by the body and insulation of your bus and thus distorted quite a bit from inside of the bus. If someone knowledgeable had been outside on the curb or sidewalk as you drove by the noise would be clearer and probably much easier to identify. Is it possible to to get a video like that? OR if you had a way to attach a camera under the vehicle from somewhere like the middle (side) of the bus pointed forward that would do it. It's more the SOUND that would be helpful rather than the camera lens which by luck might be pointed at the actual problem.

BUT YOU KNOW WHAT? I am going to recommend this: DON'T EVEN DRIVE THAT BUS unless it is to an inspection or to have work done on it, or unless you really must drive it for other purposes and there are two reasons: #1 SAFETY, your own and for others on the road. Something could possibly break and affect the steering or brakes. Since we don't know what the problem is yet, it's better to play it safe. #2: and this is the far more likely scenario than a safety failure: When problems like this occur, they need to be diagnosed and fixed as soon as possible before this problem results in damage to OTHER parts which then becomes more expensive.

Like I've said, I don't think you need to worry because the problem will be easy to identify as soon as it is inspected. See my reply to david85 after it gets posted.

1991 Ford E350 7.3 IDI short bus. I am also getting a front end wobble. It's not a wheel bearing or stuck caliper. This is not constant, happens sporadically.

 

[Fixnstuff]

OOOPS, sorry a post was so long, I had to edit out a couple of things that I missed because I'm starting to be in a hurry this morning, but I forgot to address the last part of your original post which was:

1991 Ford E350 7.3 IDI short bus. I am also getting a front end wobble. It's not a wheel bearing or stuck caliper. This is not constant, happens sporadically.

THAT is something for the Alignment Shop and something that needs to be THOROUGHLY INSPECTED AND PROPERLY FIXED. That does not always happen a alignment shops, they CAN miss some important things and that is what I want to advise you about so you can be sure that the inspection is thorough and everything is fixed right the first time. That's what will be in my reply to david85.

There are probably a number of worn parts in your steering assembly that will need replacement. HOW MANY MILES ARE ON THAT BUS if you don't mind me asking?

 

[Fixnstuff]

When your steering is completely fixed with proper alignment you are going to be very happy. When mine was finally fixed properly after bringing it in 3 times in about 8 months I WAS REALLY HAPPY. It drove like a brand new truck! So don't fear getting this done right! And hopefully the first time.

 

[Fixnstuff]

Max Mini,
I just now watched your longer video where 'the crew' got under it to look. They checked the wheel bearings, ball joints, brake calipers and rotors SO THE GOOD NEWS IS: IT WASN'T THOSE!

So you should be HAPPY, not sad.
I can tell you THIS MUCH, the vehicle needs to be raised up on a rack in order to properly inspect it and that is why the wonderful crew you had looking at it didn't find the problem (and I am sincere by calling them a wonderful crew because THEY TRIED and what they did inspect appears to have been done properly.
They weren't prepared for looking further than that.

I noticed that the noise started after you drove over some railroad tracks and I'm going to guess-ti-fy that something in the steering assembly and/or parts associated with it is badly worn out.
Is it safe to drive? What would a professional shop tell you? Lets assume they had not driven it to feel and hear what the problem is and had not put it on a rack and inspected it to find the problem.

Due to heavy liabilities if they tell you something and then the vehicle gets in a wreck they could be held liable and sued so they would probably tell you to drive carefully, take it home and park it until you can bring it in for inspection and repair.

It looks like your next stop is going to be an alignment shop. AND I want to give you my personal advice and instructions on pretty much exactly how to handle this. It's important so make sure you get the advice before proceeding. If you have already called for an appointment let me know right way because I'll have to run this to you fast. If you haven't called yet, DON'T until you've read the advice. The first part of it will be in my reply to david85 and the second, maybe a third half of it will be directly to you.

I got very little sleep last night which is why my posts are too long... lack of concentration.

I hope I can get this done in time because I am swamped here. I have a very important doctors clinic appointment in a few hours and lots to do to get ready for that. The chore that I forgot was taking the garbage and recycle bins out to the curb and while I was writing this the garbage truck passed by. I ran outside and flagged him down and he said he would come up the other side of the street in awhile and pick it up. I wanted to be out there for that so I could throw it in myself and I did. So now another load of laundry to start and other stuff and I might just get this all done in time.
I feel like a dummy for typing all this stuff but they don't have to read it and even if it is long winded the advice (which I think will be good) is free.

 

[Fixnstuff]

I forgot to mention. As far as driving it, I would suggest that it's probably safe for in town driving at city speeds but keep it at a minimum. Leave extra following distance ALWAYS not just in this instance. These are big heavy vehicles and they don't stop on a dime like modern little cars. More distance will give you MORE TIME to slow down for an emergency stop and THIS will give the people behind you more time to stop, preventing you from being hit from behind. Most accidents are caused by people following too close (rear end collisions) and when you leave more distance in front of you that gives everyone behind you more time to slow down and stop in an emergency situation and you just saved everyone behind you from getting in a wreck (or many of them).

I would suggest keeping it off of the highway if you can. You want to have that problem identified and fixed before it gets worse and possibly causes damage to another part which could have been avoided.

 

[Fixnstuff]

-

>snip

- Different elements of it were noticed at different times. I have noticed an occasional sort of a "bang" or "pop" that seems like it's coming from under the driver's side, but very sporadically, for a few months.

Do you remember if this happened while making a very sharp turn at very low speed? Happens when the wheel is turned sharply like you are making a 3 point turn to change your direction on a street? Mine was doing that on a very sharp left turn at very low speed (I never turn sharp going fast). This turned out to be caused by: The steering gearbox was very worn out, well beyond any hope of an adjustment helping. It needed to be replaced.

That is something that an alignment shop SHOULD INSPECT BUT SOMETIMES the alignment techs are too young and don't have enough, IF ANY experience with the big old Ford IDI diesels and they miss things. Even the older guys can miss some details and that will usually show up with an alignment that did not fix all of the problems. For example a steering wheel that pulls to one side or another after everything else has been fixed can be caused by worn caster or camber bushings and it seems that is discovered by ruling out everything else. ALL OF THIS WORK, 3 DIFFERENT TRIPS to two different Les Schwab alignment shops was completed for the cost of the first alignment. Everything else was FOR FREE under the Warranty for the original alignment. The last trip to the alignment center was for the bushings and that diagnosis, work, and half of the work from the previous visit was done by the shop manager. He was DETERMINED to get everything right and he did!

These young guys are used to working on Hondas and Nissans and Toyotas and the NEWER American made cars and trucks.

- Yes, big vibration in the steering wheel, however, NOT with the noise. Separately.

I am going to guess-ti-fy that they are in fact related

 

[Fixnstuff]

Some unexpected things came up, including a long long call from a medical insurance company about changing a policy with lots of questions and hoops to jump through leading to more phone calls I had to make. Being really tired today from lack of sleep I'm burnt out with only enough time left to get ready to go to an important doctor appointment so I won't be able to get back here to make my last comments and advice until about 10:00 PM Eastern Time.
I'll have to close this out for now.

 

[Scotty4]

Some unexpected things came up, including a long long call from a medical insurance company about changing a policy with lots of questions and hoops to jump through leading to more phone calls I had to make. Being really tired today from lack of sleep I'm burnt out with only enough time left to get ready to go to an important doctor appointment so I won't be able to get back here to make my last comments and advice until about 10:00 PM Eastern Time.
I'll have to close this out for now.

Too bad we just moved or I would have been able to come help take a look. Just left Bremerton!

 

[Max Mini]

Some of the comments have given good suggestions and advice but that is A LOT of stuff to try to remember and check.


AN ALIGNMENT SHOP COULD MOST LIKELY IDENTIFY THIS PROBLEM DURING A FREE PRE-ALLIGNMENT INSPECTION. I use Les Schwab Tire company because there are only a couple of choices in this little town. They have excellent equipment, really good warranties on the work they do and some free services like free tire rotations.... BUT THERE IS SOME OTHER ADVICE THAT YOU NEED TO KNOW and I'll give you that advice in a reply to david85 after I post this and make some coffee. and a couple of other quick chores (start a load of laundry and I forgot what else)


BUT YOU KNOW WHAT? I am going to recommend this: DON'T EVEN DRIVE THAT BUS unless it is to an inspection or to have work done on it, or unless you really must drive it for other purposes and there are two reasons: #1 SAFETY, your own and for others on the road. Something could possibly break and affect the steering or brakes. Since we don't know what the problem is yet, it's better to play it safe. #2: and this is the far more likely scenario than a safety failure: When problems like this occur, they need to be diagnosed and fixed as soon as possible before this problem results in damage to OTHER parts which then becomes more expensive.

Like I've said, I don't think you need to worry because the problem will be easy to identify as soon as it is inspected. See my reply to david85 after it gets posted.

Hey there! I took your advice before I even had it and stopped driving right after I made this post, though I did take it to the only alignment shop I trust that can handle the vehicle size, and they were even more jammed up than my mechanic.

Do you remember if this happened while making a very sharp turn at very low speed? Happens when the wheel is turned sharply like you are making a 3 point turn to change your direction on a street? Mine was doing that on a very sharp left turn at very low speed (I never turn sharp going fast). This turned out to be caused by: The steering gearbox was very worn out, well beyond any hope of an adjustment helping. It needed to be replaced.

I finally got in to the mechanic today, and I just got the call -THIS IS THE WINNING ANSWER! Steering gearbox is being replaced today!

I'm sorry it took me so. long to respond but I finally just decided to leave the bus on their doorstep in the assumption that they would fix it sooner if it was in the way, and once it was out of the driveway, I kind of went into denial. They JUST got to it today. In fact I didnt even know you had responded and I was coming back to say what the diagnosis was, and there you were, with the right answer!