1966 C10 LY6/6L90 Swap Transmission not Shiftting
 

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

More info. Did John S provide the setup?

Is it going in to gear but staying 3rd?

Any DTC's being posted?

Is the TCM running a stock calibration or modified?

What year was the TCM/trans from originally?

Was the TCM re-programmed with a different year calibration?

"Seals the TCM to the trans case" do you mean the connector seal or the filter plate that seals the TCM to the valve body?

Hello RSZ28,

John reworked a harness I provided to him. He also reprogrammed the PCM and TCM, but I am not sure what was exactly done. I assume just the basics to get the setup to run in the truck. The transmission appears to be stuck in 3rd while driving. The only DTC I am getting is P0700, but John told me I need to get a better scanner as the code is just a generic. I am looking for a suitable scanner for a DIY'er, but have not found any yet.

As for the combo, the complete setup is suppose to be from a 2007 Silverado 2500HD.

As for the seal, I was referring to the one for the connector. The funny thing like I said earlier is if I disconnect then reconnect the TCM plug or battery, everything shifts fine until I shutdown and restart the car. I am trying not to take it to the dealer because it is a custom application and who knows what they'll say the root cause is for the problem.

Ly6/6l90
 

You have to post or send me pics of this setup. A few questions:

-How is everything working and have you had any other issues?

-Where did you get the wiring harness redone at or from who did you get an aftermarket harness from?

-Was the truck originally a factory "low hump" transmission and did you have to modify to clear the 6L90?

-What gears did you use in the rear diff?

Email me if easier at [email protected]

Trans Tunnel
 

Never mind about trans tunnel as I saw where you had already told me that it was the high version. Thanks