Hi guys, I'm experiencing a woo-woo-woo noise. It seems it's coming only while the engine is under load, or it gets louder, with the more load. So..if I'm driving on the highway, and I go up a hill, it gets louder when the engine works harder. If I let off, it goes away instantly. 

 

It sounds like something is off balance to me, I'm just not sure what could be making the noise, only while the engine is under load. I pulled the front drive shaft. The wheel balancing weights are still on tires. Tires, brakes, rotors, hubs new in the last 15k or less..and this is a new development. 

 

Any ideas to look at? Here's a video..you can hear it pretty clear at 15 sec in. 

 

How many miles on the truck?

 

Are these stock injectors? 

 

You might consider having the injectors pop tested. Then you might do a valve lash make sure the valves are not too tight or too loose. Worn injectors can do some weird things. 

1 minute ago, Mopar1973Man said:

How many miles on the truck?

 

Are these stock injectors? 

 

You might consider having the injectors pop tested. Then you might do a valve lash make sure the valves are not too tight or too loose. Worn injectors can do some weird things. 

I think she's at around 215k 

Stock as far as I know..only smoke I get is a puff when it starts up. Stock hy35. 

 

I've actually been wanting to do a valve lash..but truth be told, I'm not entirely sure how to get the front cap off. I guess truck vents out back and has a "12v" cap up front. Not sure if it screws in or I pry it off..didn't want to break it, and it didn't seem to budge budge. 

 

Pop test involves removing them I'm sure? Big money? Heh.

6 minutes ago, Exalted85 said:

I think she's at around 215k 

 

215k those injectors are done. 

 

6 minutes ago, Exalted85 said:

I've actually been wanting to do a valve lash..but truth be told, I'm not entirely sure how to get the front cap off. I guess truck vents out back and has a "12v" cap up front

 

Unscrews. Normal thread.

 

6 minutes ago, Exalted85 said:

Pop test involves removing them I'm sure? Big money? Heh.

 

The average price is about 9 to 15 dollars per injector. This just pressure testing and no adjustment,

Does it appear to be engine related or drive train? The video didn't help me.

 So many things could cause this, it does sound like something is out of harmonics. So I would check harmonic balancer first, definitely need to make sure your valve lash is set right. With time as valves stretch you lose your clearance, and when the motor is under load and it gets hot, you may have some valves that are not fully closed, this is just a wild guess. Since you have automatic it could be something to do with your transmission, it could be a rear driveshaft also. It could possibly be excessive AC noise coming from alternator affecting your electronics when it's under the load. 

Start at one place and work your way around the only thing you can really do. Have you checked for any codes just in case.

How much load are you under?

 

Do you have a boost gauge?

 

3 hours ago, NIsaacs said:

Does it appear to be engine related or drive train? The video didn't help me.

 

Honestly not sure..it sounds like it's coming from the front to me, which makes me think engine. 

 

2 hours ago, Dieselfuture said:

 So many things could cause this, it does sound like something is out of harmonics. So I would check harmonic balancer first

 

Short of looking at it while running, anything I should do? This reminds me..my alternator housing came loose a little bit, and I had a clicking up front..solved by tightening it down..could this have damaged something? 

 

I'll try to do valves this weekend..I think it's raining tho, of course :/ provided I can get the cap off. 

 

when you say transmission..I was trying to reproduce it, and I almost think it's only happening in OD. I remember reading something about imbalanced drive shaft causing od housing to break, could this be happening? Would I just take it to a trans shop to dx?

 

Did the wt mod, ac noise at all time low.

 

I do get a random speed sensor code. Just replaced rear..replaced trans maybe 5k ago. Back plug feels a little loose to me, and it did have metal shavings..I'm assuming because I had the rear diff rebuilt recently..but the code still comes back.

 

49 minutes ago, AH64ID said:

How much load are you under?

 

Do you have a boost gauge?

 

 

Generally not much..20pct load, maybe 5psi..I can't detect any boost leaks, but I'll try to take another look. I did note it was getting worse with higher load, which is also more boost..I think 45pct load / 15psi was going up hill. I have to drive a grade this morning..I'll try to video or take note

Is it speed based or rpm based? Meaning if you maintain speed and downshift does the frequency change?

7 minutes ago, Exalted85 said:

 

Honestly not sure..it sounds like it's coming from the front to me, which makes me think engine. .

 

I do get a random speed sensor code. Just replaced rear..replaced trans maybe 5k ago. Back plug feels a little loose to me, and it did have metal shavings..I'm assuming because I had the rear diff rebuilt recently..but the code still comes back.

 

 

 

That's a bad sign, I would pull the cover and at least change the oil and take a good look. Drive train noise can be hard to pin point, the sound can telegraph itself almost anywhere.

4 hours ago, AH64ID said:

Is it speed based or rpm based? Meaning if you maintain speed and downshift does the frequency change?

Seemingly not speed based..I can be cruising at 80 with 20pct load and no problem. Doesn't seem to be rpm based either.

 

I took it up a pretty big grade today..dropped od, I think I was going about 26 load, 13psi, 2100 rpm..no noise. I'm really starting to suspect od. 

 

It seems to come in randomly too, though..but only when I'm in the throttle. The rear drive shaft is spinning full time, right? If it was that, it should do it not just under load?

@Exalted85 the front cap is normally hand tight but if it's too tight to loosen by hand you can use an appropriate sized oil filter wrench. Another way to adjust valves is to watch the valve rockers on cylinders 1&6. Bar the engine over until you either see the valves in overlap on either cylinders 1 or 6, by overlap I mean you will see both the intake and exhaust valves being slightly open and there will be zero clearance between the rockers and cross heads on the cylinder in overlap on both intake valves and exhaust valves. If cylinder 6 is in overlap both rockers on cylinder 1 will have lash and vice versa if cylinder 1 is in overlap.

 

If cylinder 6 is in overlap you adjust 1I, 1E, 2I, 3E, 4I, 5E then bar the crank shaft over 360° where cylinder 1 is in overlap and adjust 2E, 3I, 4E, 5I, 6I, 6E. I=intake E=exhaust. I've set valve lash many times by watching valve rockers like this when timing marks are impossible to see.

 

Nominal valve lash for a 6BT and CM550 (CM551) ISB is 0.010 for intake and 0.020 for exhaust with engine temperature less than 140° Fahrenheit.