Airplane under my hood

[rhsub]

I have a noise when driving at highway speeds that I am having trouble locating. This noise sounds like a cross between a airplane propellar and the coolant fan under full load. I have removed the coolant fan and clutch assembly and the noise is still there. Here are all the symptons; engine must be at full operating temperature, speed 55 mph +, worse the faster you drive, changes pitch when you hit a bump or dip, does not appear in other gears (4 th lock up only),worse under load going up hills, this noise is there most of the time but sometimes will disappear for a few minutes. My wife doesn't like it:). Noise is loud enough that you have to talk loudly. Any imput would be greatly appreciated
Thanks Ron

[Warren96]

First of all,let me be the first to welcome you to the ''Page''. What are the RPM's on yours at 55 with 4.10 gears? On mine with 3.42 gears it has to be around 16 or 17 hundred.

[DennisG01]

At first, it was sounding to me like an exhaust leak -- it might get worst when you go over a bump since your right foot may bounce on the throttle a little. However, an exhaust leak would be there all the time. The "must be warmed up" and "only does it in 4th gear" is confusing. Are you sure? Maybe you're only hearing it when you're in 4th/locked because the engine noise settles down? Besides, if you went slow at lower speeds to try and hear better, you may not be making enough exhaust pressure for the noise to be noticeable. I had a leak in my crossover that sounded like that - actually it was a few small holes starting to appear/rust through.

[TAG]

U - joints or a front wheel bearing.

[simon]

rearend, transfercase? tranny,driveshaft steady bearing.

[rameye]

torque converter??? pretty darn loud when they go.

[garre1tt]

Does it sound like a turbo prop propeller, more of a wine? Could be the turbo.
If it sounds more like a fan blade hitting the shrowed it could be the harmonic dampener.
looks like we all have our guesses, let us know what you find.

[DaveNY]

Sounds like something grounding out on the fender well or floorpan at certain torque output (maybe loose mtr mount or escaped socket or wrench wedged somewhere?) Downpipe touching frame? Had this kind of thing happen on big truck @ work.
Dave

[joe bleaux]

White or red?


Joe



Does it sound like a turbo prop propeller, more of a wine? Could be the turbo.
If it sounds more like a fan blade hitting the shrowed it could be the harmonic dampener.
looks like we all have our guesses, let us know what you find.

[DennisG01]

White or red?


Joe

maybe a rose, instead?

[Robyn]

Hmmmm
Unfortunately this sort of item can be very hard to diagnose on a text only forum.
Everyones perception of sound is so different in how they describe it.

Now can you make the rig do it while its standing still?
Will the noise remain if you hold the RPM and shift the trans into neutral?
Will the noise remain with the rig going at speed but the trans in neutral and the engine at idle?

There are several items that can make attrocious amounts of noise.
A torque converter can make noise when its not locked due to the failure of the thrust bearings.
When locked up they will generally not make any noise as there is nothing moving inside the converter itself.

Will the noise remain with the trans in 3rd gear and the converter locked?

3rd gear is straight through with no gear train running.

If the noise is only in 4th with power on, the overdrive planetary set my be on its way down the toilet.

Do you get excessive noise in any other gear range as the rig is accelerating?


You might also try checking the accessories on the front of the engine.
A failing water pump bearing can make a lot of noise but it will present itself even with the vehicle standing still.
Power steering pumps and alternators can make noise too but also they will do so without the vehicle moving.

Other items in the drive train such as wheel bearings and differentials can make noise but will usually do so no matter what the gear range.

If you have a badly leaking turbo connector hose (Turbo to air hat) it could make a screaming sound under load. Also if the boot that connects the air filter to the inlet of the turbo is broken you could hear a loud whine

Check it out and see what you get. If its only 4th gear Im betting the OD is on the way out the door.

Let us know

Robyn

[N9Phil]

When my right front wheel bearing went bad I first noticed it when I was going 50 to 55 mph and it acted the same way as yours. It is an easy thing to check. Jack up the front end and put a bar under the tire and lift up. If the bearing is bad you will be able to feel the play in the bearing. Do both front wheels and if one is bad you will defiantly be able to tell.
N9Phil

[More Power]

To add to what Phil and others have posted, I'd look at the front wheel bearings. I had this same problem some years ago. I swore it was engine related because the annoying sound resonated with the engine. Not till I noticed it would get worse/go away when cornering did I suspect a wheel bearing.

In my case, I had driven through deep water a few months earlier, which eventually resulted in a front wheel bearing problem.

Jim

[rhsub]

Did a lot of checking and road testing, I think I have two sources of noises which can really screw up the diagnosis.
1st noise sounds like a non turbo diesel with the air cleaner removed, happens between 1900 and 2200 rpm, it is there in lower gears but not as loud, goes away when you put it in neutral and let engine idle at 65 mph, this may be a normal noise but it seems to be to loud, I have checked all the accessories for bearing noise at idle and they are quiet, I checked the timing with a tech 2 and it is a tiny bit advanced, bounces around 4' and the GM spec is 3.5' don't know if this might be a problem. I have the wrench to turn the pump but if i remember right the nuts are a real pain to get at. I fixed a small exhaust leak at the turbo outlet but that didnt help any.
2nd noise. when I was coasting at 65 mph I could hear a hum that I suspect is a wheel bearing, my only problem now is figuring out which one because it isn't loud enough yet to hear with a stehascope on the hoist, and those bearings are two expensive to change unnecessarly, anyway going to see if I can borrow/steal a pair of chassis ears for a couple of hours
Thanks for all the imput and wish me luck
Ron:cool:

[94bluehd]

If your TC is a New Process 241...I had the same problem until the front input bearing finally went out.. Found a good place in NV to supply a rebuild kit and great cust service.

[JTodd]

Wheel bearings are easy enough to check. While driving, if you hear the noise, grinding, moaning, clicking, while turning to the right, it is the right side bearing or vice versa. They tend to make more noise when weight is shifted away from them.

If that does not work, lift one or both of the front wheels off the ground. Grab the top of the tire and try to wiggle in and out. If it moves at all, you need to either repack the bearing (for a shorter term fix) or replace the hub. Note: wiggling while grabbing the tire at the 3o'clock and 9o'clock position might be deceiving as you will be including the tie-rod play.

You may want to check your drive shaft as well. They can make some strange noises as they loosen up.