Started having a severe vibration problem with 87' Chevy Blazer, 350 C.I., 4X4 recently. Short history: Had 33X12.50X15 offroad mud tread tires put on 7 months ago, developed bad tread wear on right front tire due to shock wear, (chopped up, uneven tread wear). Rotated tires and put new shocks, (4), on front chassis. Rode fine for a week. All of a sudden, I have a very rough ride, vibration wise, ONLY when I am accelerating or have foot on the gas cruising. If I back-off the gas, vibration goes away and ride is smooth. Also, about the same time this started up, noticed an intermittent squeel noise coming from what sounds like rear wheel. This also stops when I back-off the gas. Checked the undercarrige and brake lines, couldn't see anything obvious. Don't know if these two things are related or not. Any suggestions would be appreciated. Thanks