6 spd klacking 3rd & 4th loaded

[WCrovo]

While towing within weight limits 18,500 lbs. my trans made a klacking sound under load up hill 6% or greater, in 3rd and 4th gear. I searched the threads and found a bunch are doing it but no answer or resoultion to problem. shifter felt smooth just a noise no vibes felt. What the F is up. Mine is a SWB so no carrier on drive shaft. I've got over 20,000 towing miles on her and never noticed this before. Usally I've got the cd player rocking but my wife was with me and I was enjoying the company. Other than a minor intermitent 3rd gear clash when cold it works perfectly. The noise dose not sound correct to me and the dealer will never duplicate it. Any ideas guys I'll be out of warrenty and I don't want a pile of gears on some mountain pass somewhere where Moses lost the tablets.

 

[klenger]

I usually notice the noise pulling a steep grade with full load in 5th gear (out of 6). Sounds like a tire going flat. I've thought that it was the transmission, but last time the wife was with me and she says the noise sounds like it's comming from the right side (front axle?), not the center where the transmission is. Could it be something with the front axle vibrating?



ken

 

[GDouglas]

As for the noise coming from your right front fender, a lot of people of TDR have had concerns with the snorkel that feeds the air filter housing collapsing with the higher levels of boost on bombed trucks. It seems that one can get a few more pounds of boost when really pushing the truck loaded versus empty when bombed. Seems that some folks have removed the snorkel all together and the "flat tire" sound has gone away. HTH.

 

[RustyJC]

Torsional Gear "Rattle"

WCrovo,



Is there any particular RPM where the noise is worse? I've noticed the same thing in the higher gears when we're pulling our 5ver, especially if RPM's drop below 2000 on a grade where I'm "leaning" on the Cummins. It sounds like torsional gear "rattle" to me, and if that's the case, there's not much that can be done short of changing the torsional characteristics of the ISB - not something I'd want to play with without a torsional analysis in hand! Hopefully, New Venture took this into account when the NV5600 was designed and gave the gears the safety margin to handle it.



Rusty

 

[WCrovo]

My rpms are over 2,000 probably closer to 2,500. I'm not floored but am at about 3/4 throttle. It is a flapping sound. Weird. I thought it was the hwy at first. What I heard was not the snorkle bobling around, mine is secure. I ck it because my 99 was falling off when I got it. It dose sound like a flat tire.

 

[klenger]

GDouglas



Interesting thought. My truck is totally stock, and I am operating at altitudes above 7000 feet when it happens, so I would expect that the boost is not as high under those conditions. I don't have guages so I can't tell actual numbers. I think I might try removing the snorkel next time and see (hear) what happens.



Thanks

 

[RustyJC]

Originally posted by WCrovo

My rpms are over 2,000 probably closer to 2,500. I'm not floored but am at about 3/4 throttle. It is a flapping sound. Weird. I thought it was the hwy at first. What I heard was not the snorkle bobling around, mine is secure. I ck it because my 99 was falling off when I got it. It dose sound like a flat tire.

Sorry, please ignore my earlier "gear rattle" reply. I guess we're talking about two different noises.



I had the snorkle "flap" noise under high RPM load before going to the BHAF (it'll do it even if it looks to be securely mounted - it flexes). With the BHAF, I can still get some "whoop-whoop" type intake noise under the same conditions. I'm convinced that it's turbulence in the rubber intake hose due to its curved design leading into the turbo inlet (not a good thing) - we require an absolute minimum of five (5) pipe diameters of straight pipe going into the blower or turbocharger intake on our engines.



Rusty

 

[Fuzz]

Compressor Stall????

I have had this noise,at least I think it's the same. Noticed it more

when towing,relatively high RPM,and then shifting either to lower or higher gear. In discussing this with Kevin Arts,he thought that the Turbo was cavitating. Kinda like a compressor stall on a Jet engine.

This makes sense to me,as it didn't happen everytime and since I have switched to the BHAF. I haven't had it happen.

More and better airflow,or maybe I 'm shifting better,letting the turbo airflow keep up???

This a thought to ponder,or not.

Fuzz

 

[RustyJC]

Compressor Surge

Yes, the noise I'm hearing sounds like compressor surge (or stall) caused by the vortices in the incoming air. This would be expected with the 180* turn the air has to make immediately prior to the turbocharger compressor inlet. Obviously, Cummins/Holset has provided one beefy impeller, because one would normally expect to see fatigue-driven fractures of the compressor blades on the impeller if operated in this mode for extended periods of time - I haven't heard of any compressor impeller failures to date.



Rusty