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Thread: Physical clunk from somewhere on driveline

  1. #1
    Join Date
    May 2020
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    Georgia
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    Post Physical clunk from somewhere on driveline

    Hi all, as of recent I've been experiencing a strange clunk with my car. This only happens going highway speeds, and most noticeably around 65mph. What happens is that if I'm coasting down the road and press the gas, I can feel a fairly strong clunk as if something is physically moving. Once the clunk happens the car accelerates normally, but it definitely feels like a delay in power delivery. This only seems to happen in overdrive. If I hit the gas hard enough to force it to drop down to second (of which I rarely do - I usually just turn off O/D to kick down to third) it doesn't clunk.
    I have yet to check the driveshaft U-joints, but I do plan on doing so when I get around to doing the transmission fluid soon (of which is bright red but smells a bit burnt - it was last changed a bit over 20k miles from the PO but that was back in 2007) and differential oil. The car is currently almost stock, the only thing that would affect driving would be the Marty tune I have installed, although I can't recall if it did the clunking prior. I've tested the engine mounts too and they appear to be in fairly good shape given its age and low miles (43k). The transmission is not J-Modded (yet)

    A buddy of mine has a 2002 Grand Marquis LSE and he seems to experience the same issue as I do - perhaps it is related to the age of our vehicles since they're within a year of age. Fingers crossed it isn't related to the transmission.

    If I have time I may try and get a video for y'all to better describe my issue.

    Thanks.
    2003 300B Mercury Marauder
    Built 01/22/03
    Purchased 01/29/20
    ~40k Miles

    Electric water pump
    Underdrive pulley
    Back and rear window tint
    Marty tune

  2. #2
    Join Date
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    Most likely, you're feeling gear backlash in the rear differential.


    2016 Ford Mustang GT PP - Lund nGauge, BMR vertical links

    2004 Mercury Marauder - Eaton M112, Billetflow 3.4, Accufab SBTB + Plenum, T-56 Magnum, 4.10s, Stainless Works LTs, 2.5" Exhaust, Borla Stingers, Ridetech Coilovers + Adj rear shocks, FX-R projectors, Wilwood 13" BNSL6 + FNSL4 BBKs, S55 Gauge Cluster
    440rwhp & 406rwtq Tuned by Adam @ Revolution Automotive
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    (Sold) 2003 Mercury Marauder - Stainless Works LT's, Stainless Works 2.5" Catback, JLT Intake, Mo's Xcal4 Tune
    5377/7839

    2000 BMW M5 - Evolve Intake, Evolve Alpha-N tune, Stoptech ST-40 BBK, UUC SSK, Dinan front STB, Dinan RSB

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  3. #3
    Join Date
    Jun 2008
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    Waukesha, WI
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    I'm wondering if the clunk is present in overdrive because the torque converter is probably in full lock up?
    You "feel" the difference because you want to "feel" the difference. Since you just spent money on the upgrade you "have" to feel the difference

    I'm looking to eliminate the double pump process I have to follow right now to get the pedal hard

    2004 300A Procharger #0010 D1SC
    2003 300A Procharger #0017 D1SC (SOLD. Last I heard, it was in Washington State)

  4. #4
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    Possibly a bad u-joint. Also check for a loose or broken suspension part.

  5. #5
    Join Date
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    Rear upper control arm bushing??
    2003 DBP # 153 Whipple 3.4 in coming soon
    2004 Black Trilogy #43

  6. #6
    Join Date
    Aug 2011
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    Quote Originally Posted by Comin' in Hot View Post
    Rear upper control arm bushing??
    That's what I'd look at closely.

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  7. #7
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    Quote Originally Posted by Comin' in Hot View Post
    Rear upper control arm bushing??
    Iíve annihilated 2 complete sets and never heard any clunking. Just a seriously unstable dog walk feel..


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    Cobra short block / ProCharger F1-A / Cog drive upgrade / Manley valves / Brian Tooley Racing valve springs / 80# inj. / -8 fuel line / -6 return / Aeromotive 340 pumps and regulator / 2012 GT500 TR6060 six speed / twin disc clutch / Driveshaft Shop GT500 upgraded CV joint shaft / BA5000 blow thru MAF/ 4.10's / Ford Racing 31 spline set up and Girdle / Metco D.S. safety loop / Stainless Works headers, cats, and everything else out back / ClassGlass hood / Bob's hood strut mod / Hurst line lock / Metco control arms / Addco front and rear sway bars / Monroe severe duty shocks all around / Race concepts rotors / Badgeless grille / 35% tint / FBM's interior LED kit and ambient lighting kit / Pioneer FB700 deck / kenwood speaker 4 Ch. / Rockford Fosgate 10" sub and amp / Kicker 6 X 8's all around / back up cam / bluetooth / Pioneer Xm / 704 RWHP 603 RWTQ tuned by Mo's Speedshop.

  8. #8
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    Quote Originally Posted by Mr. Man View Post
    Possibly a bad u-joint. Also check for a loose or broken suspension part.
    I wiggled on the driveshaft when I had the car on ramps; it's solid. Didn't wiggle at all.

    I've gotten the parts I need to do the tranny fluid and rear diff fluid in so I'll be doing those this weekend. I can inspect the rear end and see how everything looks.
    2003 300B Mercury Marauder
    Built 01/22/03
    Purchased 01/29/20
    ~40k Miles

    Electric water pump
    Underdrive pulley
    Back and rear window tint
    Marty tune

  9. #9
    Join Date
    Apr 2020
    Location
    Spokane WA
    Age
    24
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    22
    I think that's a feature of the 4R70/75, it's happens on both my 08 vic and less so on my 03 marauder. Same exact conditions you describe, cruising at 65ish and you lightly get back on throttle

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