Relative motion between engine and frame?

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pstrang

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May 4, 2006
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Some of you may recall that I've been struggling with the 1800-2000 rpm droan/vibration ever since I got a MBRP 4" turbo back exhaust. I've had the TSB done on the turbo pedestal, aligned and re-aligned the exhaust dozens of times both hot and cold, added weights, clamps, tried w/ and w/o the cat and/or muffler, and most recently had my driveline precision balanced. It sucks, can't kill it. Truck is so smooth at 55-60 and then again at 80+ mph, but in between is getting on my nerves (where I spend most of my time).

What if I attached the downpipe to the frame with a custom aluminum bracket? Hopefully that'll reduce any vibrations coupling into the body. But then I'd be worried about some relative movement between the engine and the frame when I rev the engine. I don't want to break anything with the downpipe and frame hard-mounted together.

Obviously the truck rocks when I rev the engine, but the frame does too. Do you think the engine twists on its mounts like the old hot rods?
 
DO NOT ATTACH THE EXHAUST TO THE FRAME. I did and it about drove me nuts. It resonates terribly!
 
Thanks guys.

Can you think of *any* other way to dampen the droan?

BTW, since I balanced the driveline, the droan seems to peek at 1700-1750 now. But still hangs around 'till 2000 rpms.
 
Take the muffler out, droan solved. LOL Actually, I saw someone made a resonator to fit inline, but I went with a Grand Rock, QP muffler, Much quieter, not droan, (until I put the intectors and turbo on), and picked up .6 MPG over 3 tanks of fuel. Its big, but it works very well.
 
If its that big of a deal just put the stock exhaust back on. There are alot of possible outcomes to the mods we put on are trucks and sometimes we have to suffer for something annoying to get better performance or what not.
 
Dalpilot said:
Take the muffler out, droan solved. LOL Actually, I saw someone made a resonator to fit inline, but I went with a Grand Rock, QP muffler, Much quieter, not droan, (until I put the intectors and turbo on), and picked up .6 MPG over 3 tanks of fuel. Its big, but it works very well.
Click to expand...

Thanks I'll research that part.

BTW, I did try without the MBRP highflow muffler (installed the delete pipe). I don't recall if it lessened the 1700 rpm droan or not. But it did introduce a more violent moan/droan at 1500 rpm. I put the MBRP muffler back on...solved the 1500 rpm problem, but the 1800-2000 rpm droan remains. :(
 
I have the same problem with my 4" Magnaflow, well not that bad but it is noticeable at the same rpm level. I believe it is the down pipe causing the noise. I just live with it, I mean, it was worth 20 hp or so, what's a little noise
 
Yea, but I focus in on it now. You'd think I could just turn up the radio, but it vibrates my foot on the go pedal and I feel it in the steering wheel too.

There's got to be some way to squash it.
 
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