I've learned a lot from this site Thank You. This is my first post. I have a 99 3500 4x4 that makes a metalic sound almost like a bearing going bad. It only does it at full throttle pedal to the metal, let off 1/4" noise goes away. It doesn't matter load or engine speed. It's an automatic but the noise sounds like it's coming from the engine compartment. I have 43000 miles on it. Any ideas? Thanks

 

Gregor:<br>I think that you should check the backflow valve. Mine was noisy.<br>george

 

Smokey - I couldn't find any thing on backflow valve what and where is it? Is it also called the overflow valve? Again the noise is only at full throttle with kick down switch engaged. No other time. Thanks

 

Noises are the worst thing to try to diagnose without hearing the rig run. This is a shot in the dark, but my suggestion is that you take it to a really good transmission shop, not a dealer unless you are still under warranty, but someone that has a top notch reputation for knowing their way around transmissions. Have them check the torque converter to be sure it is not working loose from the flexplate, or that the lockup solenoid is operating properly and the lockup clutch is releasing like it should.

 

Gregor,<br><br>I'm new here too, but I wanted to give my 2 cents worth. I've got a '99 3500 also and it makes the same noise that you explained. Like my Dad always told me, &quot;Son...If it aint broke, don't fix it...&quot; <br><br>I believe it's coming from the turbo somewhere. Maybe someone can reply and let us know if there is a turbo &quot;overflow&quot; for pressure, or a wastegate in there somewhere. In otherwords, I believe that it's normal, nothing to worry about. I've got 55k on my truck and it sounds &quot;metallic&quot; also when you stomp the pedal down to it, let off and it goes away. <br><br>Just FYI,<br><br>See Ya..

 

Nother 3500 here, makes a slight noise. I'm coming up on 113000 and runs better every day.

 

Gregor:<br>The backflow/overflow valve on my truck had a broken spring. At WOT, the spring CLICKED. I diagnosed for almost a year.<br>Just worth checking.<br>george

 

Took it to the dealer today. They had all their top mechanics take it for a ride. Conclusion? They said there was a discontinued TSB for the throttle cable rattle where it goes thru the firewall.They didn't fix it. So I'll check it out tomorrow. Anybody know of this TSB? -Gregor

 

AFAIK this TSB is about a rattle when using cruise control. <br>The TSB reroutes the throttle cable .<br><br>2c<br><br>AlpineRAM