Ok..I have a wierd problem

[creekhead]

It seems when I am cruising on the Highway...around 65 to 70...once in a while I get a wierd shake...like a vibration...Just out of noplace

I have no lights indicating any problems....the wierd past is that when I get this...if I back off the peddle or hit the peddle...it is gone...instanltly...wierd
I drove it 4 hours ove the weekend and it was doing it about every ten minutes or so...It's got me stumped...
Any idea would help BIGTIME...it's driving me buts and I have a long trip coming up soon

BTW it's a 1996 with a 3.8 in it

THANKS!

[rhb3]

I had a similar shudder at highway speeds in a 1997 3.8L with ~142k miles. I did three things and now it's gone:

1) Changed the coil
2) Changed the plug wires
3) Changed my transmission filter and fluid (50% change by dropping the pan only)

I should note that I had recently changed the plugs (a few months ago) but you should certainly consider that while you're in there! I really suspect #3 helped me the most as I negelected the transmission completely.

HTH,
Rich

[kurtr]

I'm not a mechanic, but my guess is going to be the tranny is near the end of its life. My 98 3.8L with 75,000 miles did the same thing -- but the cruising speed was more like 45-55 mph. Accelerating or decelerating would make the vibration disappear. The other symptom of our failing tranny was a loud clunk shifting into 2nd gear at slow speeds. (The new tranny still clunks going into 2nd, but not as loud).