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Vibration From A Dead Stop

My 2001 Outback has developed a problem in the last few days. When I move the car from a dead stop, I go through a brief period of heavy vibration coming from the back of the car, exactly as if I am running over a rumble strip. It occurs as I am accelerating away from the stop just after the clutch is totally let out. Once I get to a high-enough velocity, I no longer feel it. However, if I maintain a very low velocity I can feel some vibration but not quite as pronounced as it was coming from a dead stop. I have been able to make this happen in 1st and 2nd gear, I have not tried in 3rd, 4th and 5th. It does not happen in reverse. I tested the clutch by putting the car up against the back wall of my garage, revving the engine and putting the car into 4th and 5th gear and the car stalled, as it should. The clutch did not slip. This clutch has about 60,000 miles on it. The previous clutch was replaced at about 85,000 miles. The problem has been getting worse steadily during a just completed a 700 mile holiday round trip. Could this be the clutch? Could it be something in the transmission?

It could be the clutch, but it could be a problem in the rear end also. It’s sort of unusual for a clutch to go out at 60,000. In fact it is unusual for a clutch to go out at 85,000 in my experience. Mine have lasted considerably longer than that. But it could be the clutch, sure. There are anti-chatter components (springs, etc) in a clutch that could be on the fritz and would cause this symptom. Or just the clutch disc is about to wear out, but still not slipping enough to fail the test you did. Does this car have a rear differential? If so, double check the fluid level there. Or the differential could be failing – there’s something called a “3rd member” that can cause this symptom, or if you have U-joints in the rear drive train, one of them could be failing. Do you hear any not-before-heard “clunking” noises when changing directions from forward to reverse? That’s a sign nof a U-joint problem. Also, make sure all the wheel lugs are on to spec. Loose wheel lugs can cause a symptom similar to this.

Thanks for the info, George. For what it’s worth, I checked the level of the clutch fluid and it is within expected range. This car does not have a differential, I don’t think. I could not find the transmission fluid dipstick; it was not where the manual said it would be. You are right about the lug nuts. I will check them tomorrow. No clunking noises. Nothing unusual other than this vibration.

I think on an outback the transmission’s dip stick is near the firewall, somewhere near the steering column, down a ways. It is usually yellow.
Isn’t this just a regular Subaru Outback, AWD? I don’t think they made a FWD or did they? Subies have been AWD since lassie was a pup, no?
If your car is indeed AWD, your rear differential is that large pumpkin looking thing in the middle of your rear wheels. There’s fluid in there that needs to be replaced periodically.

It has turned out to be a frozen universal joint. On this car, you can’t just drop in a new joint, you have to replace the whole axle.

Thanks for clearing the thread…

“It does not happen in reverse.” That’s strange…Was the boot torn or missing completely, allowing the joint to run dry??