Engine scream/whine noise starting around 39 or 40 mph

[TexAndy]

Picked up another deuce today at Ft. Sam It's a whistler. It's got that distinctive whhrl just like my pampered deuce.

However... I noticed another noise that started around 38 - 40 mph. A sort of high pitched jet engine scream noise that increased in pitch the faster I went.

Take the foot off the accelerator and no jet engine scream. Put foot back on the accelerator and the scream comes back.

Any ideas? It's been awhile since I drove my other whistler, so maybe that's just a normal noise but I can't really recall hearing it before...

 

[Flyingvan911]

I think your newest whisler is louder than you're used to. How about on the highway at 50-55? My whistler likes to make jet sounds too.

 

[TexAndy]

I didn't get it up to 55. I kept around 45 mph the whole way back since it was a recovery trip.

50 MPH it had the jet engine scream, slightly higher pitch than at 45.

 

[nk14zp]

You might want to check for boost leaks.

 

[yamabro]

Are you sure its in the turbo, could be in the chunk

 

[TexAndy]

How do I check for a boost leak...

chunk of wha?

 

[yamabro]

The differential, a buddy of mine had one do the same thing till it final grenaded

 

[TexAndy]

oh.

Yeah, I felt the hubs after I got back. The rears were kinda hot. Couldn't hold a hand to them for more than a second. 110 mile trip.

The fronts were only warmish.

 

[yamabro]

I would at least give it a good look over. Hate to see you shell that out

 

[TexAndy]

Well, I do have one complete rear axle leftover from a truck I parted out awhile back.

What should I look for? Should I take the axle shafts out and check the splines?

 

[yamabro]

I would start simple first to rule out any other alternative. check the oil, Black, dirty, metal shavings???
Do any of the axles look Old, New, Rebuilt?
Any visible leaks?

 

[TexAndy]

okay, just went out and checked the two rear axles.

both had dark green gear oil in them to the proper levels. both appeared to have lot of little bubbles in the fluid. At first I thought it was metal shavings, but on closer inspection, I think it's just bubbles.

However, the middle one did have some dark powdery grey sludge in the fluid. Felt gritty on my finger. I think that might be metal shavings.

The axles appear to be arsenal rebuilt. They had tags on them, but they'd been painted over. Everything on the truck has a nice paint job on it, actually.

The middle axle had some old grimy leakage around the plug. I'm assuming because the relief vent was plugged (like they always get).

 

[TexAndy]

Ok, checked again in daylight. Used a metal magnet wand.

No appreciable amount of shavings in either axle. Checked the transmission case too with same result.

There's a diesel mechanic down the road about 30 miles who said he might be able to listen to it and look at it on saturday.

Would it be best to keep the speed under 40 mph when I do that? I'm assuming so.

 

[goldwing2000]

You were under the truck for a long time... did you check the t-case, too? Making a noise under load but not unloaded can sometimes be t-case. Something in my drivetrain screams like a banshee above 50mph but all the fluids are good so I'm just gonne drive it until something lets go.

Also, turbo noise won't steadily change with vehicle speed. It will vary based on throttle (which controls turbine speed) and is generally much slower to react to driveline load changes. It has to spool up and spin down.

 

[TexAndy]

I did not check the T-case yet. Will do that before I head over to the mech.

The thing that makes me think it's something in the axles is that the hubs were kind of hot. Not SUPER hot, but hotter than they should have been.

I did not think to feel the center/pumpkins tho. If that part is significantly hotter than the hubs, I'm going to guess that means it's the actual differential gear.

If it's not, then I'm going to guess that it might be some of those bearings inside the axle housing.

Or the hot wheel hubs might just be a separate problem, completely unrelated to the noise.

 

[goldwing2000]

You're right about the hubs. My fronts are almost always warmer than the rears, due to more side-loading from turns and such. I drove 4 hrs down to WPAFB and my rear hubs never got above "room temperature". Definitely check for temp differentials between center sections and hubs. If the middle is cool, it could just be wheel bearings or dragging brakes.

 

[TexAndy]

Oh, I didn't even think about the brakes. And I did do some brake work on the truck before I headed off the lot.

Bled the brakes and and took the breather vent out of the MC cap because it was plugged. If it was sitting for a long time, I guess some of the WCs could have been stuck.