99 100 high mileage mystery noise... transmission?

[REZARF]

I have a '99 100 series with 385k and it is awesome.

After my most recent 1500 mile road (montana to colorado and back) trip this month I have noticed a noise that is RPM related, only when in gear, usually as the RPMs are above 2500. Only thing I noticed was my charcoal canister burping at 10,000 feet in the Colorado high country, but that is pretty normal.

The truck pulls, shifts and is as smooth as it has been for the last 385k miles but there is a NOTICABLY intermittent louder noise now.

I have had three friends listen to it, here is their description (I agree with their descriptions).

• It sounds like water slamming into the inner fender wells when you hit a big rain puddle.
• It sounds like a large volume of rushing air (but very loud).
• It sounds like its coming from the drivers side area vs. the center or passenger side of the vehicle.
• Not screeching, squealing, or grinding like a bad bearing, but in volume it is similar that you can tell something isn't right.

It is happening pretty regularly now like 20% of every drive. I drained and filled the fluid, only got about 2.5 quarts to come out (I do this part of my regular oil changes and have for a long time). I cannot get it to make this noise in neutral, it is only when in gear. It happens in L, 2, D the same.

Again, the truck is shifting fine, not slipping, not grinding... seems to be driving the same. There are zero leaks on this truck. But DANG, something is wrong. I am at a loss as to what to try to look for. Going to do some pleasure reading in my factory manual tonight. Any ideas of what to check or what this could be would be a real help.

 

[89BIGBLUE]

Fan clutch?
Exhaust leak or loose shield!
I dunno man, just thinking at it.

 

[SteveH]

If it happens at reasonably slow speeds, can someone else drive past you as you stand at the side of the road and listen/watch as the truck goes by?

It's not a plastic fender liner rubbing on the tire at higher speeds/wind levels?

 

[REZARF]

If it happens at reasonably slow speeds, can someone else drive past you as you stand at the side of the road and listen/watch as the truck goes by?

It's not a plastic fender liner rubbing on the tire at higher speeds/wind levels?

Steve, thanks man.

I don't think so, but I will try. It is pretty consistent now. However, the car is running exactly as before... just MUCH louder. Sounds like rushing wind.

I know its not the fan as it only happens in gear. I can rev the engine all day and nothing. It's only happening while moving.

 

[REZARF]

Fan clutch?
Exhaust leak or loose shield!
I dunno man, just thinking at it.

Thanks, it isn't the fan as it happens only when in gear.

Exhaust leaks in my experience have more of a ticking sound, this sounds like a large volume of air is rushing. Going to crawl under it tonight for a closer inspection of everything.

 

[89BIGBLUE]

Doe

Steve, thanks man.

I don't think so, but I will try. It is pretty consistent now. However, the car is running exactly as before... just MUCH louder. Sounds like rushing wind.

I know it’s not the fan as it only happens in gear. I can rev the engine all day and nothing. It's only happening while moving.

Does it make the same sound in neutral or reverse?

 

[89BIGBLUE]

Steve, thanks man.

I don't think so, but I will try. It is pretty consistent now. However, the car is running exactly as before... just MUCH louder. Sounds like rushing wind.

I know its not the fan as it only happens in gear. I can rev the engine all day and nothing. It's only happening while moving.

Not wheel bearing related?