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Discussion Starter #1
Hello and thank you for your time. I know this has been talked about and I have done lots of reading but just to make sure I am understood here is the details.

this what is going on.

2005 Mustang V6 Auto

Added a posi lock rear and changed gears from stock to 3.73. Purchased all from American Muscle. Also changed rear bearings all new seals etc. Complete kit. Used royal purple oil and then put in some anti lube to help the rear end.

Now the problem started about 20 miles in it started to hummm. Low speed mid speed has a humm. Now I am at about 250 miles on the new rear end i decided to see what it will do on top end. At 100mph it vibrated so much it dam near shook me off the road. At 106 i backed off thought it was going to let go. The humming sucks but I can live with it (rather not but.....) now the vibration I can't live with.

I have been reading to see what may be done. Your advice would be greatly appreciated. I live in a small town with great mechanics but none really familiar with rear end works. Closes major center is 5 hours away.

Thanks again.
 

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i know some ppl say their new gears make noise. you might need an alignment to fix the shaking
 

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i`m kinda thinking the gears have nothing to do with the vibration. i guess it could but i would suspect other things, like driveshaft not seated properly, or bent or not balanced, a bad u joint(s), a bent or damaged axle, a bad wheel or even a real bad tire balance issue. its a pretty serious issue if its that bad.

a mechanic should be able to check all that stuff, check the runout on the wheels, remove the rear wheels, bolt the rotors down, run the car in gear to eliminate wheels and tires, runout with a indicator on the axle ends to check the flanges ect. my motive gears and t lok hit around 100 quite often and its as smooth as silk.

just to dbl check, when you get this vibration, its in the body or feeling it in the seat? and not in the steering wheel at all?
 

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Discussion Starter #4
vibration

The vibration is in the car from front to back. Tires are good. I am going to turn the drive shaft 180 and see if that makes a difference.
 

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The vibration is in the car from front to back. Tires are good. I am going to turn the drive shaft 180 and see if that makes a difference.
thats a good idea just to make sure its properly installed. generally if theres vibration in the steering wheel, its something in the frt end. if its in the seat its from the rear.

dbl check the torque on your lugnuts too.

i know its time consuming and frustrating, but the process of elimination should find the issue
 

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just so you know, my friend used royal purple in his gears and it ate away at his gears and internals. He switched back to motorcraft and flushed the whole thing and had to replace the parts.
 

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Discussion Starter #7
really and they say royal purple is the best HMMMMMMMMMMMMMM.

Ok so i rotated the drive shaft 180 and it is better but not like it was. The hummmm is still there but not enough to worry about I can be happy but at 100 mph vibration is still there. Not like it was but bad enough. The old gears I could pull about 130 mph without vibration bit thee new ones no way.

HELP if any one can
 

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really and they say royal purple is the best HMMMMMMMMMMMMMM.

Ok so i rotated the drive shaft 180 and it is better but not like it was. The hummmm is still there but not enough to worry about I can be happy but at 100 mph vibration is still there. Not like it was but bad enough. The old gears I could pull about 130 mph without vibration bit thee new ones no way.

HELP if any one can
i dont know that its the best. ive never used it before but i used the rp for my break in period of maybe 500 miles, then changed it with new rp. i think ive got around 20+k on the rear end with it, no issues so far and ive tortured it plenty.

thats about all the ideas i had :)
 

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The whining sound is most likely from the gears. If they weren't installed correctly or if the backlash is a little off they will whine. As far as the vibration like amustangrocks said it is most likely the driveshaft not seated properly. Take it to the place that did the install and have them look at it. Also most people recommend a 500 mile break in period on the gears. I'm not saying you did any damage taking it up over 100 at only 250 miles but if you are having humming and vibration issues it probably isn't a good idea to do that or accelerate aggressively
 
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