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I have an otherwise well-behaved '93 940 whose maintenance is mostly up to date (wife's daily driver).
Last year, replaced center support bearing and u-joints. Had a vibration at take-off under load. All was well until almost a year later when the car has developed an increasing vibration, no noise, between 25 to 30 mph, both on acceleration and deceleration, though seems a bit less upon deceleration.
Thought I detected some u-joint slop, so replaced all three u-joints. Center bearing is still smooth and bearing retainer, less than a year old, SEEMS intact. Vibration evident in gear only. Will not emerge in park or neutral.
I put the car on jackstands, and took her to 25 with the wheels on. Vibration present. Took off the rear wheels, accelerate to 25. Vibration present. Unhooked driveshaft at trannie and ran it up to 25. Vibration absent. Re-indexed driveshaft (180 degree's at transmission). Vibration present.
The funny thing (becoming less so) about this vibration is that it is most pronounced in the steering wheel, less so in the seat. Even sitting in the driveway with the car on jackstands, the steering wheel shakes when accelerating from 25 to 30. No shake is evident when revving the motor in park.
The output bearing in the trannie might be a suspect. Sounds smooth when running, and shows no slop whatsoever. I'd rather be sure before tackling that job.
Tomorrow, I'll try shimming the support bearing, and will report the results. However, this problem is not at takeoff. The car accelerates smooth as silk until it hits 25, then starts the shakes.
Any experiences and wisdom greatly appreciated.
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