Resonance is back,need help

[Tom W]

I have done the exhaust modifications, clamps and angle iron, and each step seemed to show some improvement but now the drone seems to be louder than ever. It starts about 2000 rpm when accelerating and gets worse about 2200.
My wife has to wear earplugs at anything over 70 mph unloaded. I just recently had the lift pump replaced and adding Standyne. I disconnected the Ottomind, less power but still resonates. I am wondering if there is anything in the ECM that could cause this. The truck runs great, 36lbs boost, 21mpg on a trip from Austin to Huntsville Ala. @ 70 mph unloaded. I'll be in Huntsville for about 6 weeks, does anyone know of a Cummins shop near here? Thanks for any help. Tom

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Tom W in Austin Tx 98 24v 2500 Quadcab, auto, 3. 54, lsd, Rhino, white/driftwood, Banks Stinger Plus, Manix grill, nerf bars , DTT's TC, valvebody, cooler, Mag-hytec trans & diff, Pac brake.

 

[HEMI®Dart]

Tom,

I would double check to make sure your exhaust system is insulated from the body & frame. Use those rubber OE type hangers. Make sure the piping is not contacting the frame anywhere. Also check to make sure there is no 'strain' anywhere in the system. If a hanger looks and feels like is under alot of tension, this can & will transmit engine vibration thoughout the truck. Could this be the drone you are talking about?

I have read where flex type exhaust piping will really quiet down the droning noise. I'm not sure where in the system It would help the most. I think the guys replaced the downpipe w/ the flex pipe.

Maybe it's just the muffler causing the noise. You could try another type.

You could possibly try wrapping the exhaust with header wrap. I would do just the downpipe and see if that makes a difference. I did this and it seems to have minor sound insulating properties.

Have you done the TSB on the coolant supply hose connector?. This will cause engine howl also:
See Here: http://www.ecpe.vt.edu/~dfritz/technical/DIESEL/troubleshooting/isb_noise.htm

& here: http://www.ecpe.vt.edu/~dfritz/technical/TSB99/09-04-99.htm


Let us know what you find. #ad


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Bill R
94 2500 SLT 4x4 5 Speed, 3. 54 LS, JRE 4" exhaust, Autometer Pyro, Boost & Water temp gauges, Bosch 215 HP injectors, Timing @ 14. 7 º, JRE Stage III #4 plate 270/675, AFC spring kit, Scotty Air, Bully Dog Propane Injection, Roadmaster Active Suspension, Optima Red Tops, Geno`s Exhaust Blanket,Espar Heater (won it!), Synthetic lubes throughout.



[This message has been edited by HEMI®Dart (edited 01-10-2001). ]

 

[RamminRick]

Tom,
You could be on the right track with the ECM. I just had the dealer reflash my ECM with some new improved programing and I have noticed that my truck sounds different around the same rpm's ???

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99 2500HD Dodge Ram SLT Quad-Cab, 8'Bed, 4x4 Cummins 24V, 5 speed, Anti-Spin 410's, 4-wheel antilock, BLACK, all other options except leather and cab lights. 285 75R D Mud tires. Better Built diamond-plate toolbox, K&N RE-0880 Cone Air Filter w/pre-filter, Turbo Silencer removed, Cobra 70-LDT Remote CB, RickBuilt (removable) hitch mounted trailering flaps.

Purchased 1/18/99
16,500 miles 1/14/00
29,750 miles 1/09/01

 

[Tom W]

Bill, I'll try removing the hose restrictor. At this point I'll try anything. My noise occurs only when Rpm is over 2000 and boost is increasing, more boost,more drone. This is a resonance that is deep and penetrating, you can feel it. My exhaust isn't touching anywhere but it could be under strain. I'll check that tomorrow.
Rick, I used to work for IBM servicing typewriters many years ago. My territory was Greensburg, Latrobe, and Ligonier. I wore out several VW's on RT 31. Thanks for the tips.
Tom

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Tom W in Austin Tx 98 24v 2500 Quadcab, auto, 3. 54, lsd, Rhino, white/driftwood, Banks Stinger Plus, Manix grill, nerf bars , DTT's TC, valvebody, cooler, Mag-hytec trans & diff, Pac brake.