My sons 91 Silverado has a bad clunk when.

My sons 91 silverado has a bad clunk when shifting from park to other gears, worse when shifted to drive. We changed tranny mount, filter, center support mount, tranny tail shaft seal, and pinnon gear seal, also u joints at tail shaft. Truck was shifting nice and smooth, then I noticed his
steering coloum was coming apart at the hub so I put back together. And it started cluncking again, however I retarded the timing to bring idle down a bit and it started shifting good again. I also replaced neutral safety switch.
Any help would be greatly appreciated
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