As some of you might know, I've been chasing a rubbing/grinding/whooshing sound for the past few months and nobody can figure it out. It seems like it first started when I towed a heavy load a few months ago. It became much louder and more obvious when I took a trip to the mountains a couple weeks ago.

The noise seems to be coming from right under the cab (transmission area). It can be felt in the floorboards and is reminiscent to the sound of air whooooossssshhing under the truck mixed with a rubbing/grinding sound. When it got really bad in Tahoe it started to make the noise around my transmission shift points althought that could have been a coincidence, because the transmission still shifts GREAT, never slips or hunts for gears. It also seems to only make the noise when the truck has been driven for 30 minutes or so (meaning it is heat related).

I have taken apart my transfer case and the internals looked good. The u-joints are new and still move very freely. All the fluids (tranny, t-case, differentials, engine oil) are very new.

I'm at a loss here, nobody can figure out where this is coming from, including a professional at a transmission shop.

Last night the sound came back. When I let off the throttle at 30 or 40mph it would coast, but the RPMs did not drop and I could hear the rubbing sound coming from under the truck again. It would continue to make the noise until I accelerate again or until I depress the brakes, at which point the RPMs would start to drop as normal. It was almost as if the truck was trying to ride the gear down like a manual transmission would. I'm thinking it is the torque converter but I have no clue. Maybe gear howl from the rear diff? Any ideas are appreciated. Sorry for the long post.

 

Could it possibly be a water pump going bad?

 

What makes you think that?

 

Does it have a locking torque converter? And if so is there any way to disconnect it to see if the problem goes away?

 

I'm not sure I've ever heard of a locking torque converter... And how could any car remain operable after "disconnecting" the torque converter?

Anyhow, I don't believe I have a locking torque converter. This is the stock converter...

 

when your on the highway nd u let off the gas do you get the same sound until you hit the gas again?

 

Not sure, haven't tried that yet. It's really hard to produce the noise when I want to, it just comes and goes as it pleases... Why do you ask?

 

Many vehicles with automatic transmissions have an electronic clutch added to the torque converter. When this clutch is engaged it locks the converter to deliver power to the trans with no loss due to slippage, when unlocked the converter will work the same as a normal one. The converter staying locked when it's not supposed to be will cause the trans to drive the engine RPM up when coasting just as you have described in your original post. When I said disconect it I meant disconnect the locking mechanism (on the ones I have seen just removing a wire will disable it, but my experience with these things wasn't with a ford so yours could be different). Many vehicles started using locking converters in the late 80s to early 90s, I'm not sure when Ford started using them though since my truck has a manual.

Added on edit: The reason I suggested this is because a friend of mine had a Chevy where the lockup converter stuck. The RPM stayed up with the vehicle speed just as a manual would, and when coming to a stop the car started bucking and making sounds/vibrations similar to a slipping clutch until the trans finaly stalled the engine. You wouldn't have gotten the bucking because you weren't coming to a stop, but if the sounds and vibrations seemed similar to that of a manual trans with a slipping clutch then the converter may be the culprit.

 

because when i was on the highway and if i let off the gas i got that rubbing/grinding noise i think your describing. But when i was on the gas again, it went away. I just replaced my universal joint at the rear end and now it doesnt make that noise anymore.. im wondering if you put too much stress on the U joint and now the u joint is shot mayb? Mine as REALLL bad... check it out

 

Yeah I think I saw your u-joint, and mine are brand new so I don't think that's the problem. Not to mention the fact that I just had my driveshaft off when I dissembled my transfer case and I rechecked the u-joints and they were fine. I WISH WISH WISH I could fix this problem with a simple u-joint

And as far as I know, these E4ODs do not use an electronic locking clutch... But I've been wrong before...

 

Did you check the rear end? The differential could be passing that sound transfer through the driveshaft. Aren't there bearings in the housing of the diff case? I'm just trying help you think of what wrong. Put it seems that it's harmonic, which could mean that the problem isn't where you hear it...Make sense? I know I 've had trucks that made the exact same noise when I let up off the gas...It ended up being an axle being worn, and when the torque was released off the driveshaft and it could basically just coast, I would hear it, but under acceleration it would go away...

 

Shot in the dark here, I know some f150's have them not sure if yours does. Hanger bearing on the rear driveshaft possibly. Those have been known to make some darn near impossible to diagnose noises/vibrations, especially at certain speeds or rpms.

 

Good point...! I call it a saddle or carrier bearing, don't know what it's actually called.....

 

He's got a carrier bearing under his truck, but I think it's been replaced recently as well.

He's also got an E4OD, which does have a locking torque converter. I really don't know that much about automatics, so I don't know if it's the torque converter or not. I can't really imagine how a converter would make a whooshing noise though.

Personally, I am leaning towards it being the rear axle. Possibly a carrier or pinion bearing, or maybe the gears themselves. I think it just *sounds* like it's coming from further up under the truck.

 

Andy's right, I just replaced the driveshaft center support bearing.

But the sound is coming from more near the FRONT of the transmission near the TC. If the sound really is originating in the rear end I'm not sure how it could get all the way up to the front of the transmission, but what the heck do I know. How much does it usually cost to have a differential rebuilt?