Note:below is about a 97 7.3 auto
Well, here I am, finally getting more down and dirty with trans tuning, I had basically been using stock shifting except for a street race file I came up with. I hadn't paid too attention to the exact shift points; I didn't make the correlation between speed in the files, and actual speed for the shifts. I only made a very few changes, just moving something up or down. Well I check and actual shift points were 20% higher than programmed shift points. So I make the change to get the shift points to match speed, actual and programmed. Take a short test run, seems OK, but I really only took note of the speed for the 3-4 shift, and its dead on. After some more driving, I find myself thinking: man, the TC is locking awful soon. I do some more looking, now TCC is locking 20% under programmed speed.
I don't remember how the TCC acted before I made the change to 'calibrate' the speed of shifts and actual(used N over V). I may try my previous files just to see how the TCC engaged before as I can't remember. Seems that I'll have to live with only having one of the shifting correct: either gear shifts or converter lock/unlock.
Initially, I had thoughts the PCM might grab a recalibrated speedo(by the procedure of grounding under the dash), but it doesn't not seem to do that. So then I was thinking that engine RPMs were used, but how would that work to determine speed when the TCC is unlocked? So does the OBS get the speed signal for shifting from the VSS in the diff? If so, then I can't figure out why the TCC lock/unlock would be different than gear shifts in terms of speed actual to speed programmed. Make any sense? If you think this "
" about me I won't feel bad.