98 chevy astro vibrates at 65mph wats wrong

Have you changed the tires and wheels? If not check speed sensor on transmission!

Hi, you could check your engine mounts.

Sounds exactly like a balancing issue. Check condition of tyres (including side walls) and get the wheels balanced. what fluid are you refering to and what's the difference between what you used to what you should've used?

your front tires are out of balance

check your wheels balance,If the problem still check your rims whether you have any slight bend,

Give us more. Only at 65mph! Can you repeat the drivability symptom?

The drive shaft needs to be replaced.its slightly bent or damaged.Check end float on both drive shafts for excesive movement.Also check for lift in the driveshaft gearbox bearings.Hope that is helpfull.good luck.

You may have to get your wheels re ballanced if you lost one of the weight's on the rim. The other thing to is a bent rim if you hit a large pot hole or crub and last to see if the tire it self has funny wear patterns on the treads.
Other things to look for if your wheels are ok. Check the ball joints Check the tie rod ends Check and pay attention to the Idler and Pitman arm. Your looking for any excessive movments
A good way is to grease all that is mentioned above and see if the vibration is gone.
Lost thing would be the brake rotors but you'ld now that by having vibrations throught out any speed when you apply the brakes to slow down.
Good luck and hope this helps, you should be able to do this on your own other then checking the wheel ballance. 

have you check the wheels. to see if there balanced right. if you jack it up and grab the top and bottom of the wheel and shack it does it move. that will be bad ball joints..check your tie rods.

I agree with chryslerpro. It usually is a tire problem. If it turns out otherwise, another item to check is a bent or out of balance driveshaft. They tend to bend after an impact or repetative towing of something heavy.