trans problem

I have a 99 suburban 4x4 that I recently purchased. When I bought it and took it on the test drive, it shifted perfectly, after driving 250 miles the check engine light came on. After paying a toll the trans shifted hard
from first int0 second. The problem is the trans does not always shift hard, usually only after highway driving. I have already changed the fluid and checked the code. it is a trans code. Anyone ever have this problem? Need a solution
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Have the PCM scanned and you'll find P1870. Your transmission needs a valve body repair or a complete rebuild if the damege has already been done. Sorry to be the bearer of bad news. I'd advise against driving it until you get it fixed, just in case it hasn't cooked itself yet and you can get away with the cheaper of the two repairs.
Doc

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