If it is vibration at the steering wheel at 65+, then it may be something as simple as wheel out of balance. A re-balance of the front wheels should fix it.

Check to see if any of the tie rod and drag link ends are loose. That would lead to looseness in the steering.

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold