Ya-Hoo!

[cleatus12r]

Just keep in mind that the OBS transmission functions are infinitely better than the SD trucks because they are so simple.

The SD PCMs are complicated enough that there are TONS of things that affect when/how the transmission shifts. The OBS computers have a tendency to do what you want them to do.....consistently.

[F-127]

Well after making my first street race tune and failing somewhat miserably by making very crude estimates on shifts (shift points were a wittle higher than I wanted), I decided I would come up with a handy spreadsheet so I could nail my shift points down more precisely, making a fine art of shifting (hopefully someday lol). So, I'm going to attach the file. Haven't got the fancy or pretty extras, but it takes care of business. Version 2 of the street race tune is soon to be completed, gonna be fun. Taking care of a number of issues, one being that "double bumping early locking garbage" as it has been put before.

[cleatus12r]

Now THAT is cool.

I wish I had some Excel skills. "You know, like numchuck skills, bow hunting skills, computer hacking skills... Girls only want boyfriends who have great skills."

[F-127]

Question time. So here I am comparing between files SD shifting and the OBS shifting parameters and I came across TV maximum for the different shifts. The SD TV max for 1-2 is a whopping 40psi higher than the OBS, which was 47. SD max for 2-3 is over double, and 3-4 is 39 psi higher. Bumping up the indicated torque just slightly and using the TV slope and offset I'd be hitting the max fairly quick. Is there any reason I couldn't use the SD values for the maximums? Maybe the higher max was to allow for adaptive shifting, which I think I read could change up to 20 psi?

[907DAVE]

Pretty sure that the adaptive stuff can do up to 30 psi, as far as the reason for the differences between the two I couldn't tell ya.

[F-127]

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.

[907DAVE]

VSS signal on the OBS comes from the PSOM (Programmable Speedometer Odometer Module), and is located in the cluster itself. The PSOM receives a speed sensor signal from the DSS (Differential Speed Sensor), then converts it to an "8k pulse per mile" signal output.