92, F150, 351W, 4x4, 148K miles.

When I put the truck under a good load, like putting the accellerator half way down or more from a stop, I get, what sounds like, a rumbling nise coming from the passenger side of the truck. It only lasts a few seconds and doesn't seem to make the truck shake. The only thing it does is create vibrations I can feel through the floor and the noise. I am having a helluva time pin pointing it. It happens more when I turn to the right and go uphill. From what I can tell it sounds like it is where the exhaust collects. The most common thing I can find is it happens under more than normal accelleration.

On the highway if I step on it I don't see any loss of power. About a year ago I had the catalytic converters tested by an exhause shop, they were OK. Not sure if they could go bad in a year.

I have removed the wheels and looked for any loose parts, there were none. The rotors and calilers have recently been replaced by a shop that I know does good work. I have also replaced my u joints (front and back) on the main drive shaft.

I really can't figure this out and that is the only reason why I haven't fixed it.

Could this type of noise come from my belt slipping? I really don't know, stabbing in the dark at this point.

Any suggestions or tests I could do to find out what this is?

 

Are you sure its not the fan kicking in? Thats the only thing I could think of that would create a roaring noise..... but I really don't know. I'd have to listen to it to be honest.

 

my air pump is the noisiest thing in my truck.

 

That could very well be it quicklook. If the tube came off the "silencer" from his air pump, it will make that noise. I know mine does!

 

all the snow on my truck will guiet the engine down some tomorrow morning.

 

How much do you got up there? I've got about 4-5 inches down here! Time to get out the snowmobiles!

 

only an inch so far but it will be snowing all night. all the idiots will be out on the road in the morning.

 

Dont worry, its a comin. We got an inch and a half in about 45 minutes. It came down in a hurry! I hope I dont have school!

 

I've never heard of an air pump, what is it and where is it located?

 

look at the fan, bottom left of the motor is the a.i.r. pump. definetly look at your clutch fan.Make sure there isnt any play side2side,and the fan should turn smoothly without fetchin up. also you didnt mention wether you had a standaqrd or automatic. could be a slight case of clutch shudder either way. check your motor mounts too(and trani mount).

 

OK, I have always been told that is the smog pump...neither here nor there, I will check it.

The fan for my radiator doesn't have a clutch but I will check all things in that area. And I have an automatic (E4OD) transmission.

Thanks.

Joe

 

I would go along with the air pump / smog pump as the possible problem. I just replaced mine - after it seized - before it did it was making variable noises. I would check it and change it before it does seize. I was close to home when mine seized so I was lucky to make it home. Just my opinion.

 

air pump or a.i.r. pump or smog pump all the same terms for the pump on the engine.

 

Do I just test if the pulley will spin freely without the belt attached? Or do I just check for a loose pulley? Any other tests I can do?

As far as I know, this is the stock pump.

Joe

 

Take the belt off and test all the pulleys. Spin them by hand. They shouldn't really spin freely. Some pulleys like on the smog pump or alternator ride on a shaft with sealed bearings at the front and back of the unit. The will keep it from spinning freely but it should spin smoothly. The grease in the sealed bearings won't allow it to spin freely but they should spin smoothly and not make a grinding noise and there shouldn't be any play in them. There may be bushings instead of bearings so they may spin more freely but again, no noise or play. Also check the idler and tensioner pulleys. Same thing there.

I had a similar problem with an old Volvo I had. But the noise was the bearing that split the two halves of the drive shaft. I can't remember what that bearing is called. It had just lost all it's grease and dried out.