TCC locking issue

[85burb]

Hey guys. My 85 burb with a 6.0 and 4l60e will not lock the converter by it self. With HPTuners i can manually lock it when driving just fine. It just will not lock by it self. My PSI harness did not come with a prndl switch connection. I am not sure what is going on. Any one have any ideas? Thanks.

[Wildkarde]

Do you have the speedo calibration screens set up properly? TCC lockup is highly dependent on vehicle speed.

There's a program an Hptuners guru wrote called BC_trans, that makes it really easy to setup trans shift points and tcc lockup points for modified vehicles. It should be easy to find with a google search.

[85burb]

I have the transmission tuned exactly like my wifes swapped suburaban and tc should lock in 4th at around 55 depending on throttle position. I have had it up to 70 with all throttle positions and it will not lock. Hers works fine. Mine will not lock unless commanded to by scanner.

[Wildkarde]

Post your current tune if you don't mind. Also the hptuners forums would probably be more help than here for an issue like this.

Is your temp sensor reading correctly? wont lockup if the engine is cold. wont lockup if the computer is seeing any misfires either.

[85burb]

I can not get my file to load on this web site. I did get it loaded at this one. https://www.performancetrucks.net/fo...-issue-553671/ The hpt forum has never been any help for me when I post an issue. Even the support people were no help.

[68c10airstream]

I would think a prndl switch input is a must. Computer needs to see this for various needs, like killing the cruise if you bump the shifter into neutral.

[85burb]

I did get it working mostly. The brake switch was working backwards. Fixed that and then set prndl switch in ecm and it no longer locked. Set switch back to none and drove it again. Converter locked. Monitored what gear it thought it was in and even with no switch set up it knew exactly what gear it was in running. Guess it know from the transmission pressure switches.

[Wildkarde]

The ecm doesn't really use the PRNDL switch for anything at all, it uses the valve body pressure sensors to know what gear the trans is in. PRNDL switch is just for nuetral safety, reverse lights, and the gear indicator on the dash. Cars didnt even have them on the trans, just on the shifter and they didnt connect to eh cm at all. I don't even hook them up on my wire harnesses unless someone wants to use it as a nuetral safety/backup switch.

Glad you got it figured out.