1998 Escort "clunk"

My daughter's escort (auto transmission) is making a single (had hard to hear, for me at least) clunk when she hits the accelerator hard going 50 mph
or above. She says it sounds like a card flapping in bicycle spokes, but it sounds like a U-joint just starting to go out on a car with a driveshaft. She wants to take it into the local garage, but I'd like to know what it might be before they give her a potentially expensive diagnosis.
Any ideas? Thanks in advance.
-John Banister
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Sounds like the cv joints going get them checked.
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hiya,
does it happen when the 'box drops into kickdown or accelerating in top gear? If it's making a 'single clunk' then look at engine mounts or exhaust hitting the floor. If it's 'card in bicycle spokes' then CV joints or gearbox bearings. Does it clunk when turning the car on full steering lock?
m
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No, it only happens on a straight road when hitting the accelerator. It does not have to drop into passing gear. It does not happen until at least 50-55 mps. I can barely hear it, but my daughter's hearing is better than mine.
-Johnn

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i would check motor mounts and the heat shields around the pipes
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