Help with cruise control after LS swap

[DocHanson]

I need help solving a very annoying issue with cruise control. I have also posted this on the HPtuner forum. Any leads on someone that could help would be greatly appreciated!

I have a 1987 60 series that I have swapped in a 6.0 LQ9 DBW setup, I kept the stock 5 speed manual transmission (H55f). I bought the wiring harness from BP automotive and have a Dakota digital cruise control panel.

Over the last several months I have spent an exorbitant amount of money and time trying to diagnosing the issue. Currently, I have cruise in 4th gear but when I change to 5th the PCM locks out cruise. As you know, the transmission is analog, so I cannot figure out why cruise doesn't work in 5th gear. BP automotive did their best and over the course of 4 months, we exchanged 100+ emails with several iterations of tunes but they finally threw in the towel. I can supply a copy of the latest tune if that would be helpful for anyone. (I can't attach the file because IH8mud doesn't recognize the file format)

I would be more than happy to pay a professional to take a look and help me diagnose the issue.

thanks for any insight.

-Gabe

 

[sims]

I know nothing about LS PCMs but I've researched LS swaps for a possible swap in my 60. Is there some sort of minimum RPM for CC to work? In your case, is it the RPM drop going into 5th taking you below some minimum value? I would think the VSS signal doesn't know gear selection so that shouldn't matter. Good luck.