If you didnīt have to loosen the DS nut for removal, then it was loose enough to collapse the two haves (but it should be tight). You say you replaced the center bushing, I assume you mean the center bearing carrier/mount (hopefully the bearing as well), so the two DS halves had to be separated to do this. Did you match the alignment of the two halves at reassembly?

Once the DS is mounted, the center nut must be tightened so the two halves can not slide. The center carrier is mounted but not tight. Tightening it is the last step. So when the car is rolled for setting, the nut and center bearing carrier must be loose just enough to seat before tightening.

After car is rolled, or rear of car bounced up and down - while on all 4 wheels - tighten first the nut, then center bearing carrier. It's important that all this be done with the car supported on all 4 wheels.

If you run the engine and DS with the car off its wheels, it's best to raise the rear trailing arms to avoid stress on the axle ball bearings at the full down position.

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