i just bought a 2000 v6 mustang and I noticed that when it is in 5 th gear it has a little shimmy when I let off of the gas going down hill and when it is on flat ground. I have driven a standard before so I know what they should feel like but I'm not sure what this might be?

 

Define "shimmy" for us. Steering wheel shaking? Wobble in front or rear suspension? Vibration in the engine/trans?

 

I would say it is more of a vibration in the trans. My friend said that it might need new u joints but if it was that wouldn't it do it through all of the gears?

 

Bump.

 

If it was the U joints, yes you'd feel it in all gears, and more so when you hit the gas.
How old is the clutch? Lots of miles/worn down?

 

I am not sure how old the clutch is. I just bought it and the car has 126000 on it. I would assume thats how old the clutch is but i don't know. Is there any way to check it without pulling the whole transmission?

 

bump.

 

Weak tranny/engine mounts.

U joints you'd feel in you butt too becuase it would vibrate the differential and subsequently your suspension.

 

It wouldnt be the clutch because i had one with 253000 miles on it and it was about to fall out any moment and it never done that to me.

 

Clutches can fail in different ways.

Another option is shell out the $30-40 and have a shop diagnose it for you. At least you'll know what you are up against and make a plan from there.