99 4L60E no fourth gear after new valve body

I had the typical 1870 codes and hard shifts after my suburban was warmed up whenever I pulled my boat. I bought a rebuilt valve body and installed it. Everything works fine, except it will not shift to fourth gear. The person I purchased the valve body from sent me another one and I have the same problem. I did not remove the separator plate this time, but I did make sure the check ball on the case side was still in place. Surely I did not get two bad valve bodies, so what could be causing it to have no fourth gear above the valve body. It worked fine before the valve body replacement. Both gaskets and separator plate looked fine and all holes are visible in plate (nothing covered up).

I had the typical 1870 codes and hard shifts after my suburban was warmed up whenever I pulled my boat. I bought a rebuilt valve body and installed it. Everything works fine, except it will not shift to fourth gear. The person I purchased the valve body from sent me another one and I have the same problem. I did not remove the separator plate this time, but I did make sure the check ball on the case side was still in place. Surely I did not get two bad valve bodies, so what could be causing it to have no fourth gear above the valve body. It worked fine before the valve body replacement. Both gaskets and separator plate looked fine and all holes are visible in plate (nothing covered up).

Recheck for codes and post back code no.

Valve body is only a band aid for code 1870.
Code 1870 is usually internal preassure leakage in transmission causing slippage.