Trans Current Gear. What does this really indicate? Take a look at this log of a 99 F-body with the MPH shift points (1-2, 2-3) set at 32, 66 and the RPMs set at 6000, 6000. (all 3 tables set the same. norm, perf, hot) Note the MPH and RPM in the log when the Trans Current Gear changes.
Current gear is what the pcm is commanding, note that that at wot the commanded gear is before the upshift occurs. The performance mode is not used unless you have a trans performance/tow haul button. Hot is used when the trans is in over heat mode.
Russ Kemp
My question is why is it commanding the next gear before the RPM parameter is reached? Seems to be doing it at exactly the MPH paramater. I'm really beginning to doubt this theory that both MPH and RPM parameters have to be exceeded before the PCM commands the shift.
I thought the VCM would activate the shift on whatever it hit first, be it the commanded RPM shift or speed???
The WOT shift speed and rpm values have to be exceeded for the upshift to occur. On the 2000 & down V8 vehicles, I have to raise the WOT shift speed to get the shift rpm right. On the V6 cars, I usually have to lower the WOT 1-2 shift rpm by ~300 rpm from what I want the 1-2 shift rpm to be. Eg, to get a 5750 rpm WOT 1-2 shift, I have 5450 entered in the editor.
Russ Kemp
Have you looked at the log I posted? What is the rpm when the current gear parameter changes from 1-2 and 2-3? I'm not a novice at this. I've been doing this for over 3 years. I'm not looking for basic explanations of how this is supposed to work. Here is the file that was in thie car when the log was run. What are the shift RPMs set at in the file? The RPMs don't drop until after the RPMs in the file. I always assumed that when Current Gear changed, the shift was commanded and it just took the transmission mechanicals time to conplete the shift. I'm looking for a reasonable answer to what this log is showing vs the file settings.Originally Posted by Russ K
Last edited by 2xLS1; 02-11-2007 at 11:32 PM.
Seems like the "short shifting" phenomenon that's being
discussed (without resolution) from the look of it. The
shift "start" is at or about the right MPH point. But I'm
guessing this may be only the first of several events
in the chain, all the band/clutch solenoids have a dance
to do and the RPM may not move until the last, not the
first. The "hang time" is only about 0.3 sec, on the 1-2.
The 2-3, that's ugly late.
I'm thinking maybe it changes on the MPH and waits for
the RPM, or something - and maybe on some OSes the
"wait for RPM" is not enforced?
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