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jenser
New User
Mar 26, 2009, 7:55 AM
Post #1 of 9
(1898 views)
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2004 Ford Crown Victoria, base model, 4.6liter, 81k miles.
I just had the exhaust changed from single to dual as well as replaced the struts/shocks, 2 new front rotors and tires all the way around. Since getting the car back from the shop I've noticed a vibration mostly when lightly on the gas around 40-45 mph. It seems to shudder, but will go away when accelerating or letting off the gas. Overall the car shifts fine and has no other obvious issues that I can tell. Wasn't sure if a speed sensor is off since messing with the brakes and wheels, I do think I have some play in my driveshaft as there is a half second delay when putting the car in reverse and hitting the gas and the car going, but i would think that would not cause vibration at certain speed would it?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 26, 2009, 8:12 AM
Post #2 of 9
(1895 views)
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If you can see any play in driveshaft u-joints that's enough to replace one or both as seen fit. They can bind without evidence until shaft is removed also and could cause the issue you have. I doubt the work just done would.
The slight delay for reverse would suggest a wildly worn u-joint that couldn't be missed with it in place so I don't think that's related by itself at the moment,
T
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jenser
New User
Mar 26, 2009, 9:46 AM
Post #3 of 9
(1886 views)
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I'm not sure what you mean on your last comment "being related by itself". I also feel that the vibration would be coming from the back of the car, after mentioning this to a friend he suggested that maybe the rear end has a gear wearing out and is not catching at certain speeds and could be slowly wearing away each time it tries to grap it.
Jens
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 26, 2009, 11:02 AM
Post #4 of 9
(1881 views)
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What I was thinking is if a u-joint was so worn that the shaft could turn that far before making contact to make a delay for reverse it would probably give you a wild "crack" sound and wouldn't last long.
Your description smacks of u-joint type vibrations common to me. If you never saw one apart they are greased needle bearings in caps (four each) and get used to one spot and make a indent there and won't vibrate. If under load of acceleration or deceleration the shaft needs to adjust the angle at the joints a bit and then you notice the bind as a vibration. Kinda need to remove shaft to know for sure on those - not a hard job.
If the driveshaft was bent somehow that can cause strange vibrations as well that may come as go with assorted conditions.
You mentioned you just switched to duals which were available OE and I've done that on older ones. Ford used counter weights to offset what I'll call a "resonance" frequency that can be transmitted thru exhaust parts. If you suspect that I could dream up some tricks to verify that but overall I think that's unlikely so far??
T
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jenser
New User
Mar 26, 2009, 1:51 PM
Post #5 of 9
(1872 views)
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Thanks T,
I'll check out the U-joints tonite and let you know what I find. I know what you mean by the exhaust, the tubed weights have been removed as I have aftermarket exhaust in place. There is vibration from that but I can deal with that, its mild.
Thanks for all you help.
J
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way2old
Veteran
/ Moderator
Mar 26, 2009, 3:09 PM
Post #6 of 9
(1868 views)
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Sorry to jump in here, but if it only does it under light acceleration from 42 to 45 mph, more than likely you have a torque converter shudder. Does it resemble running over rumble strips in the roadway? If it does, have the transmission fluid completely changed, or go to the parts house and get a bottle of trans medic anti shudder(or shudder guard). If the additive stops the problem, then have all the fluid and the transmission filter changed.
Being way2old is why I need help from younger minds
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 26, 2009, 8:03 PM
Post #7 of 9
(1863 views)
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Right on way2old. Bet it's that and not u-joint issues at all at just that speed too,
T
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jenser
New User
Mar 27, 2009, 9:59 AM
Post #8 of 9
(1857 views)
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Well, guys....first off I want to thank you for all your thoughts. Its much appreciated.
I turned my U-joints and they were good, I looked them over, so then I thought since my shocks were replaced maybe they put the wrong ones on and it was causing the driveshaft issues. Hey ya never know these days! Not the case, this time. So I drained the pan and looked at the filter, no metal pieces, hmm, well thats good I told myself. proceeded with the oil change and replaced the filter and presto it worked. I'll give it a few days and see what happens, so far so good at least better than it was.
Thanks again!
Jens
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 27, 2009, 11:03 AM
Post #9 of 9
(1855 views)
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Jen,
I have a bunch of these type cars myself and I'm fussy as all get out with shocks. The better ones or so they say don't always deliver the ride you expect from one of these. If you want it to handle like a Mustang the better and stiffer ones would probably win out on a pylon course.
I've been to hell and back getting ones that are about as good as OE and even OE doesn't always give you the exact ones used when new. Literally the $14.99 plain shock from Gabriel seems to work out great. On some you'll find the bushings aren't the OE size new in box - so reuse origs or find the right ones.
This is certainly subject to personal taste in the ride character and I'm talking about regular shocks not any air strut/spring types that might be used in this,
T
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