Need help! 1st-2nd gear shift overlap

[rbooth]

I have searched with negative results but I have been struggling to figure out why at the top of first the car seems to loss power. Well I think I have found out what is happening I just don't know how to fix it. In the attached log at frame 3294 the TCM is starting to apply PCS4 Cmd pressure for the 2nd gear shift. This goes on for 1.4 seconds causing the engine not to rev through first as it should and then it finally shifts. I would really appreciate some feed back.

Thanks,
Rodney

[SICK WS 6]

Pretty sure those PCS pressures fluctuate based on what clutch is coming in for the shift.
Watch the log and it makes sense.....
At frame 3293, C4 is coming on and PCS4 is ramping line pressure for it.
At frame 3369, C3 is coming on and PCS2 starts ramping in while PCS4 starts ramping out.
At frame 3498, C2 is coming on and PCS3 starts ramping in while PCS2 starts ramping out.

If you haven't already, setup a chart display and watch vehicle speed, rpm, and TCC slip starting at 3285.

[rbooth]

Thanks, I will do that. I get the on coming pressure for the next gear but why would it take that long to shift. When I have timing pulled during the shift the timing will fluctuate (almost like it cant make up its mind to shift or not) a few times before it shifts. I was looking at my tune and I noticed I didnt raise my max line pressure vs rpm vs gear. Not sure if it has something to do with it but the pressure in that tab starts reducing around 6000. I never had a problem until I changed to the 4000 stall so my thought is 1st maybe slipping some causing shift problems. It is very noticable in the car when I am at the track with traction. It stops pulling where it should be pulling the hardest. Is this a possiblity? Unfortunately, I only can test this at the track because when I have wheel spin it doesnt do it.

[bluegoat06]

OP, start by matching the last 2 cells of your part throttle tables , with the last 2 cells of the full throttle tables.
Example, part throttle shift table, normal mode, tps 94 and 100, you have 23, then 13 ?
then when you go to the full throttle shift, normal mode, same TPS cells, you have 12 and 13 mph. futhermore, full throttle shift rpm normal, you have 6100rpm and 6500rpm.
You're confusing the crap out of the trans.

In the G8's, mph and rpm has to be close to each other for a good shift.
Set the tps cells to 23 24 in the part throttle table for normal, then do the same for the full throttle shift (last 2 cells or tps 94 and 100), then set your shift rpm full trottle to 6500, both cells for the 1-2 shift.

In patternA (or sport mode for us with G8's), you have the same problem, part throttle is mismatching full throttle (last 2 cells), shift rpm full throttle is ok.

You can use bluecat calculator to come up with more closer mph vs rpm shift to type in those tables. look it up as 6LXX calc. the 1-2 shift mph needs to be a littler lower than what the cals tells you, i've found usually 3-4mph lower for the last cells, i guess because the times it takes for the trans to realize mph/rpm are close enough with our 4.02 1st gear ratio, 2-3 needs to be around 1mph, and 3-4 seems to be dead on.

Give it a try and that silly 1-2 issue should go away, assuming the values are specd correctly.

[rbooth]

Thanks!

I was under the impression that the 6l80 ignored the rpm and only used mph. Although I get what you saying about the mph setting confussing the computer. I will use the spreadsheet make the changes and see what happens.