1966 C10 LY6/6L90 Swap Transmission not Shiftting

[1Bad68Cat]

Hello All,

I just completed the install of a LY6/6L90 into my brother's 66 C10. I had a couple of hiccups along the way, but was able to solve them. Now I have one that wants me to pull my hair out. Initially, I had a problem with the speedo not working and the transmission not shifting. I called John @ Speartech and he gave me a couple of suggestions. Long story short I found that the seal that seals the TCM to the trans case was not fully seated therefore not allowing the TCM harness to make consistent contact. After I had fixed the seal problem, everything seemed to be working properly until I shut the truck off and restarted it. The truck did not want to shift again (although the speedo still worked unlike before). I can get it to shift again if I remove and reinsert the TCM harness or battery cable, but I do not want to be doing that everytime I shut the truck off. I have used the search function here on Lateral-G but have not found anything similar to my problem. Anyone who did this swap run into a problem similar to mine? I have an email to Speartech and hope to have an answer tomorrow. This is the last remaining issue and the truck can go back to daily driver duty. Any help would be greatly appreciated and thanks in advance.

Robert