Blazer shaking

I have a 1999 Blazer 4x4 that shakes at 75+ mph. It's not a constant shaking and doesn't seem to have anything to do with the type of road, asphalt or
concrete. The whole car will start to shake for about 1/4 mile and then quit, a few miles later start shaking and then quit. Below 75 mph it's fine.
Today I was changing the brake pads and noticed some green grease coming out of an axle boot on the front drivers side. It's slung around onto everything in a circular pattern. From what I can tell the boot looks ok, not ripped or cracked. Could there be a problem with a seal, bearing, ??, inside this boot causing the shaking.
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Hi,     Shakeing can be cause by 3 things. Your tires out of balance are the most common. They will shake only at certain speeds. Not below or above. Your drive shaft will only get worse with speed as well as your "U" joints. The last is an out of balance engine or flywheel if a manual shifter. These will shake all the time. Actually, it's more of a vibration. I doubt if your seal leak caused the shake. If you decide to replace the seal make sure that you have a good workshop manual. I found that a good combination of books is the small manual from Haynes and the big book put out by Chilton. I have a complete set. The Chiltons are expensive,(about 30-50 $$ each), but worth it. When you take off your wheel and dissasemble the four wheel drive unit/hub assembly make sure that you do not un-necessarily remove special clips or springs. Sometimes, these parts are not supposed to be dissasembled, but are removable as a whole. Most of the time these parts are only replaceble by the dealer as a unit. Your tire thats leaking grease is a good indicater that this is the out of balance wheel. Severe shaking can ruin a seal. Email me if I can help. Good luck. Jessie
NCIII wrote:

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First, let me say that a blazer was not designed to travel at speeds above 75+ mph. Now, the vibration you are feeling is of the harmonic type because it oscillates. This is caused by a rotating shaft whether it be the crankshaft, driveshaft or axleshaft. A bad u-jount could cause this or if the driveshaft has recently been rebuilt the u-joints could be out of phase because the spline joint was incorrectly aligned. you may want to check the bushing or bearing that supports the front of the driveshaft or drive flange. here are some links for you: http://www.4xshaft.com / http://www.pirate4x4.com/tech/billavista/PR-shaft/index.html Good luck
--
Mad-Dog
'79 Chevy K-10
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