Might be Exaust and NOT Rear end??

[roperteacher]

Just had an idea... the whine/ drone I get at 68-70 might not be the rear end... I was reading a post that another person believes it might be the exaust! It does have a resonating, pulsating , kind of noise... but like I said, not loud enough to really raise a sting about. How would I test this??? Could I take a piece of wood and wedge it in somewhere and go for a test drive??? THanks!

 

[timjones]

easiest way to check would be get going 70ish or were ever your grown is at and put it in neutral if the grown goes away then its engine not drive train.

 

[DPelletier]

Take a HD piece of angle iron and firmly fasten it to the exhaust system with a bunch of hose clamps. Try maybe 2x2x3/16" or larger on a straight section of pipe. If the noise goes away or changes, its the exhaust.



Dave

 

[bighammer]

I have a howling noise at certain RPMs that seems to come from the rear. It seems to be related to the turbo and not the axle speed though.

 

[roperteacher]

I have a 6 speed. If I went 70, then pushed in the clutch or went to neutral and it stopped would that really show it was engine related? I thought when you disengaged the drive train it disengaged the rear end also??? Wouldn't the noise stop anyway... . the weird thing is, it only does it on level road, not up or down hill!

 

[Johnstra]

Hey, that's interesting, bighammer.



My dealer actually replaced my turbo (before he replaced my R&P) cause he swore it was the turbo making the noise. New turbo... same noise. New R&P after the turbo swap... same noise, gradually less noticeable over 2000 miles or so.



Sigh...



I've changed my diff fluid twice since the new R&P went in. First change (500 miles on new R&P) I found LOTS of metal flakes (little curls of metal) stuck to magnet and in the bottom of the pan I drained the fluid into. Second change (about 1500 miles later), I found a few flakes but they were actually hard to find. So I think it ran in a little and the noise has decreased noticeably at low speeds. I still have a quiet howl at about 60 only on coast side.



-john

 

[timjones]

Ok going uphill you would have a high load on the engine, so more boost= more air flow



The opposite going down low load= less air flow



An engine is just a big air pump, For what ever reason at just the right air speed, pressure and temperature it sets up a harmonic imbalance which gives you a grown or growl or whatever.



As far as the rear end goes when you disengage the transmission all you have done is take the everything forward of the clutch/valve body out of the equation, the engine/fly wheel-clutch/torque converter is idling so it's not setting up any vibrations, there by giving you a "clean" sound for the drive shafts, transfer case and front and rear ends.



Just a process of elimination if its not 1,2,3,4 it might be 5 unless it interacts with 2 then its 3



Clear as mud I hope.

 

[Vaughn MacKenzie]

roperteacher, I had a whine sound in my truck for awhile. If I hauled off and kicked my tailpipe it would go away for a couple days. It did it between 45-60 and always nearly the same pitch and only when the engine was loaded somewhat.



New exhaust cured the noise. I have posted this on most threads I see discussing rear end noise but no one seems to clue in to my suggestions as if I hadn't posted anything. You're the first one I've seen even entertain the possibility.



Vaughn

 

[NSperduto]

I saw the suggestion, but haven't kicked the pipe yet. I'm not 100% sure it's the rear yet, I also think it may be the exhaust. Also because I notice it now at lower speeds intermittently. sounds like the same noise.

Also going 70 and putting it in neutral won't tell what the problem is. At least on my truck, it's between 65-70 mph and a light acceleration.



Nick

 

[roperteacher]

NSperduto, I am with you there. Mine ONLY does it between 68-70. Only on flat ground. If it were the rear wouldn't it do it EVERYTIME the wheels were moving at that speed? Shouldn't matter if it was up or down hill. THe gears still move right???

 

[roperteacher]

Oh, if I EASE my truck to the ZONE (68-70) I can reduce the noise by 80%. . barely notice it... If I heavily accelerate to the zone it kicks in right away... . would this indicate an exaust issue???

 

[NSperduto]

Originally posted by roperteacher

NSperduto, I am with you there. Mine ONLY does it between 68-70. Only on flat ground. If it were the rear wouldn't it do it EVERYTIME the wheels were moving at that speed? Shouldn't matter if it was up or down hill. THe gears still move right???

I'm not sure. I'd like to go drive some of the same trucks with a gas engine and see if they make the same noise.



I'll have to go surf around for a ram/gas engine forum

 

[bighammer]

Mine only does it up hills or accelerating when the turbo is working a bit more. I won't try to take it up with the dealer because I'm sure they would say it's the big X I took out of the intake pipe.