RPM Based Vibration Engine or Torque Converter/Flexplate? - TCCoA Forums
 
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post #1 of 9 (permalink) Old 11-01-2015, 09:46 AM Thread Starter
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RPM Based Vibration Engine or Torque Converter/Flexplate?

Hi All,

I have a 2000 Mustang 3.8 auto with 112K miles. I bought this car last year off the original owner and have been dealing with an engine/drivetrain? vibration ever since. To date, I've replaced:
-battery & terminals
-air filter
-plugs/wires/coilpack
-DPFE + EGR valve (car had CEL when purchased for P0401/402 codes)
-Harmonic balancer(no change)
-Fuel pump assy (had hard start condition in the mornings, had to cycle key to build pressure) starts up fine now
-***Trans fluid changed shortly after purchase at 103k, car appeared to have original fill, fluid was dark there was good amount of sediment bottom of pan but no chunks. Magnet had nice caked on goop.
-Filled with Castrol Mercon V after draining TC and pan.

What I experience seems to be a shudder like vibration which is RPM based from about 1200 RPM to 2000 RPM. I can replicate this sitting still in P or N. I can also replicate it to an extent if I hold gears - 1st, 2nd, 3rd, etc.

It is most pronounced in 3rd gear if I switch O/D off and cruise around 35-45MPH. It will shudder excessively here, on the throttle, cruise, AND coast down.

It is also felt in O/D on the highway under light throttle and steadY cruise around 55-70MPH.

Trans shifts fine otherwise, no slippage. Does this sound like a TC issue or maybe even flexplate issue? I have tried the brake tap test and there is no change in behavior. Would this completely eliminate the TC out of the equation?

Sorry for long post, and thanks for any help!
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post #2 of 9 (permalink) Old 11-01-2015, 10:22 AM
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Originally Posted by SilverSixer View Post
Hi All,

I have a 2000 Mustang 3.8 auto with 112K miles. I bought this car last year off the original owner and have been dealing with an engine/drivetrain? vibration ever since. To date, I've replaced:
-battery & terminals
-air filter
-plugs/wires/coilpack
-DPFE + EGR valve (car had CEL when purchased for P0401/402 codes)
-Harmonic balancer(no change)
-Fuel pump assy (had hard start condition in the mornings, had to cycle key to build pressure) starts up fine now
-***Trans fluid changed shortly after purchase at 103k, car appeared to have original fill, fluid was dark there was good amount of sediment bottom of pan but no chunks. Magnet had nice caked on goop.
-Filled with Castrol Mercon V after draining TC and pan.

What I experience seems to be a shudder like vibration which is RPM based from about 1200 RPM to 2000 RPM. I can replicate this sitting still in P or N. I can also replicate it to an extent if I hold gears - 1st, 2nd, 3rd, etc.

It is most pronounced in 3rd gear if I switch O/D off and cruise around 35-45MPH. It will shudder excessively here, on the throttle, cruise, AND coast down.

It is also felt in O/D on the highway under light throttle and steadY cruise around 55-70MPH.

Trans shifts fine otherwise, no slippage. Does this sound like a TC issue or maybe even flexplate issue? I have tried the brake tap test and there is no change in behavior. Would this completely eliminate the TC out of the equation?

Sorry for long post, and thanks for any help!
If it's doing it in part and neutral and occurs at a fixed RPM range my guess is going to be flex plate or converter. As in out of balance or cracked. Not as in fried clutch shudder. Another possibly would be something out of balance on the front of the motor. EG a PS pump issue, belt misalignment some AC clutch related. Sloppy tensioner etc. although something in the accessory drives usually makes its self known by squealing. Still it a area to check. Not sure about the 3.8 but if they are using hydra kicky damped motor mounts one or both could be bad and letting a vibration through that would normally be damped out. V6s are know to shake some and it's often more prevalent at a certain RPM. You've done the plug wires which is good. It's possible to have wires bad enough to give a misfire shudder but not set a CEL misfire code. I had a intermittent shudder that was load and and RPM sensitive on a relatively new set of wires. It wasn't enough to be bothersome just annoying and since the wires were newish that was the last place you'd look. Finally at about the three year mark on the wires it started throwing a misfire code and a new set of wires cured that.

Regarding the wires. My buddy whose a 40+ year mechanic pointed out that in the old days of oscilscope tune up machines the misfire would have shown up immediately on the scope. But on new cars we tend to lean on OBDII data almost exclusively. If you know some one with a old fashioned tune up machine or scope and can have them look at the ignition pattern it may show something up. Just throwing that out there.

I'd have as friend run the car at the vibration range and take a look at the accessory drives on the front of the motor. Also see what's happening with the motor mounts at that RPM. Think about getting it scoped to see if there any weirdness in the ignition
pattern. And pull the inspection plate on the trans and give it a good look for a cracked flex plate.

Im sure others will have some good advice too.
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post #3 of 9 (permalink) Old 11-01-2015, 12:09 PM
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You can rule out accessory drive vibrations by just removing the belt entirely to see if the vibrations persist.

Motor mount or FP/TC vibrations are my thoughts since it doesn't appear to be related to a specific RPM range vs load relationship, or a condition where it only happens in drive (in which case I would have suggested having a look at the MAF sensor).

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post #4 of 9 (permalink) Old 11-01-2015, 05:02 PM
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You can rule out accessory drive vibrations by just removing the belt entirely to see if the vibrations persist.

Motor mount or FP/TC vibrations are my thoughts since it doesn't appear to be related to a specific RPM range vs load relationship, or a condition where it only happens in drive (in which case I would have suggested having a look at the MAF sensor).
Excellent point on just pulling the belt. Should be noted that since your not going to be turning the water pump with the belt off you would want to make this a fairly short test. Possibly with a cool motor if the vibe is present regardless of operating temperature.

I've seen both hydraulic and solid rubber motor mounts listed for MN12s. I don't have any idea which applications used which. But I wouldn't be surprised if the hydraulic ones were used on the V6 to absorb the extra roughness. If that's the case you may see some signs of leaking fluid.

I'd also check to see if having the AC compressor running makes any difference. While unlikely it could be some sort of rumble or resonance going on in the lines. Fairly far fetched but I've seen lines shudder.
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post #5 of 9 (permalink) Old 11-01-2015, 08:34 PM Thread Starter
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Thanks for suggestions everyone.

Prior to changing out the harmonic balancer, I had run the motor without the drivebelt and vibration was still present. This led me to change the balancer which made no change.

With regards to how it runs with the A/C: I noticed a few times this summer that the car shuddered/vibrated a bit more with the A/C running a few times while cruising on the highway. If I'm not mistaken from some research there is some programming or correlation between the A/C clutch/switch and TCC/solenoid and lockup?
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post #6 of 9 (permalink) Old 11-01-2015, 10:02 PM
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Originally Posted by SilverSixer View Post
Thanks for suggestions everyone.

Prior to changing out the harmonic balancer, I had run the motor without the drivebelt and vibration was still present. This led me to change the balancer which made no change.

With regards to how it runs with the A/C: I noticed a few times this summer that the car shuddered/vibrated a bit more with the A/C running a few times while cruising on the highway. If I'm not mistaken from some research there is some programming or correlation between the A/C clutch/switch and TCC/solenoid and lockup?
I can't say. I do know at least on the 4.6 the AC Clutch disengages at WOT. I presume the 6 is the same. But unless you've changed something via tuning the PCM it think it's unlikely. Otherwise it would be a common issue more people would have with the stock tune. Changing the balancer had no effect? So we can assume that it wasn't damaged during the install process?
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post #7 of 9 (permalink) Old 11-01-2015, 10:21 PM Thread Starter
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Originally Posted by 97CatMan View Post
I can't say. I do know at least on the 4.6 the AC Clutch disengages at WOT. I presume the 6 is the same. But unless you've changed something via tuning the PCM it think it's unlikely. Otherwise it would be a common issue more people would have with the stock tune. Changing the balancer had no effect? So we can assume that it wasn't damaged during the install process?
Correct, balancer has been eliminated from equation as changing it didn't change anything. Balancer is new OEM Ford and I used the proper HB removal and installation tools.

2000 Mustang 3.8, auto, 112k mi.
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post #8 of 9 (permalink) Old 11-02-2015, 06:40 AM
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One quick check would be the converter to flex plate mounting hardware. Make sure they are all tight.
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post #9 of 9 (permalink) Old 01-20-2016, 12:51 PM Thread Starter
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Update:

I ended up dropping the car off at a Ford dealer for full diagnosis and had a tech road test it. Spoke with the tech and he believes it is indeed a vibration due to an imbalance. He noticed the HB looked newer which I confirmed was replaced which led him to believe it could be either in the flywheel or possibly the balance shaft in the motor. I asked about the converter and he said it's a rare but possible if the converter threw a weight internally causing an imbalance. Either way, to further diagnose the flexplate/converter would be to pull the trans ($833+t) and of course "no guarantee" if it turns out to be inside the motor.

The vibration is felt in P/N and any gear pretty much first appearing around 1300 RPM, then smooths out, then re-emerges at 18/1900 RPM, then smooths out above that. He stated that otherwise the engine is in healthy running condition. Not what I wanted to hear, but at least closer on to something.

2000 Mustang 3.8, auto, 112k mi.
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