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06-15-2017, 01:03 PM
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700 HP Mach
 
Join Date: Nov 2003
Location: Orlando, FL
Posts: 8,384
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"Thumping" sound on decel?
any thoughts on what to look at? Im not sure if its just a byproduct of tolerances in the aftermarket parts or what
Truetrac 31 spline diff Moser 31 spline axles (with c-clips) FRPP 4.10s MT ET streets in case that somehow matters. Also has Steed upper and lower control arms (might be transmitting more noise?) on decel I'll get a rotational thumping type noise from the rear of the car. If I put moderate pressure on the brake pedal it will stop. When originally chasing this I found that my rotor pros rotors had a little wobble to them (we'rent true). Those have been replaced, did not check the new ones before installing them. I also saw that the driver side rear rotor was very close to the caliper bracket, I spaced the bracket out with washers and now both sides the rotor appears to be pretty well centered in the caliper. Apparently thats not uncommon with aftermarket axles.
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03 dsg mach1 - MPR built 9.5:1 motor, D1, cams, ported intake, full exhaust, magnum t56, built rear, E85 etc... '12 F150 FX2 Supercrew with Ecoboost daily beater |
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06-15-2017, 01:52 PM
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#2 |
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Can't be bridled
Join Date: Sep 2007
Location: Texas
Posts: 7,006
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Re: "Thumping" sound on decel?
Did this come out of nowhere or did it happen after a launch? Does it have a drive-line feel to it or a suspension feel?
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2004 Mach 1 #6956 5spd w/IUP Eaton swap, longtubes, built 3.73 SRA 452hp/409tq dynojet🏁 |
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06-15-2017, 02:19 PM
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#3 |
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Registered User
 
Join Date: Aug 2011
Location: Rogers, AR
Posts: 1,070
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Re: "Thumping" sound on decel?
http://www.mach1registry.org/forums/...t=gear+install
Check this out. Maybe it is the problem, maybe it isn't. Worth a shot!
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2003 AB Mach 1 Build date: June 19, 2003 -P1-SC kit -Magnaflow Catted X w/ Borla Stingers -MGW Shifter -H&R SS springs -18" AFS reps -Treated better than my wife |
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06-15-2017, 02:39 PM
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#4 |
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700 HP Mach
Join Date: Nov 2003
Location: Orlando, FL
Posts: 8,384
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Re: "Thumping" sound on decel?
I looked at that link, theres no noise while accelerating or cruising. Im going to do some better trouble shooting this weekend if itll stop raining for a bit.
this setup has made the noise from the beginning and it doesnt always do it. This rear end setup came out of the MM&FF project car, it did it on that car when I had it and does it on mine too. I just havent been able to drive the car much until recently so now Im noticing/chasing gremlins like these
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03 dsg mach1 - MPR built 9.5:1 motor, D1, cams, ported intake, full exhaust, magnum t56, built rear, E85 etc... '12 F150 FX2 Supercrew with Ecoboost daily beater |
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06-19-2017, 01:39 PM
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#5 |
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Registered User
 
Join Date: Jun 2011
Location: Midland, Texas
Posts: 787
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Re: "Thumping" sound on decel?
Is the noise in sync with the speed from which you decelerate? I.e. is it faster when slowing down from 70mph versus slowing from 40mph?
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No accident that my birthday is March 1st. Take out the 'r' and you end up with.... 2003 Torch Red Mach 1 ★ Rebuilt 3650 & MGW ★ Spec 2 & Fidanza flywheel ★ H&R Super Sports & Maximum Motorsports struts/shocks ★ Maximum Motorsports rear lowers, MM panhard, MM caster camber plates ★ Mosers + ARPs ★ Brembo slotted rotors, braided lines ★ Catless X and SLP LM2s ★ 18X9/10.5 - Toyo R888R |
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06-19-2017, 02:17 PM
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#6 |
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700 HP Mach
Join Date: Nov 2003
Location: Orlando, FL
Posts: 8,384
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Re: "Thumping" sound on decel?
yes, it decreases as speed decreases, its in line with wheel speed. Unfortunately I didnt get a chance to play around with it this weekend to see if it matters being in neutral vs in gear or trying to figure out if some sequence of events triggers it
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03 dsg mach1 - MPR built 9.5:1 motor, D1, cams, ported intake, full exhaust, magnum t56, built rear, E85 etc... '12 F150 FX2 Supercrew with Ecoboost daily beater |
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06-19-2017, 04:46 PM
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#7 |
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Registered User
Join Date: Jan 2013
Location: San Diego, CA
Posts: 1,104
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Re: "Thumping" sound on decel?
My guess would be the diff. Those worm gear diffs are known for making more noise than others. When you press on the brake you're probably applying just enough force to take up whatever slack is in there.
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New Ride: 2004 Mystichrome Cobra-Accufab SBTB and plenum, Steeda 2.8" upper, Bassani X, Borla Stingers, Mcleod RXT, MGW shifter, Level 5 halfshafts, chrome FR500's, Stiffler's FIT system and DS safety loop, GT pumps, BA3000, tuned by owner |
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06-19-2017, 06:54 PM
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#8 |
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700 HP Mach
Join Date: Nov 2003
Location: Orlando, FL
Posts: 8,384
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Re: "Thumping" sound on decel?
If that's the case I can live with it just trying to narrow it down
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03 dsg mach1 - MPR built 9.5:1 motor, D1, cams, ported intake, full exhaust, magnum t56, built rear, E85 etc... '12 F150 FX2 Supercrew with Ecoboost daily beater |
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07-01-2017, 06:34 PM
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#9 |
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Registered User
Join Date: Jun 2007
Location: Las Vegas
Posts: 1,086
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Re: "Thumping" sound on decel?
True tracs are a bit more noisy than a clutch pack diff.
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