Tranny not obeying commanded Downshift points

[Bill@HPTuners]

Ok I was out helping a friend adjust his part throttle shift points on his lightly modded 00 SS camaro...full exhaust, built tranny with a small converter(hes not sure of what size/brand), 3.73 gears, computer was tuned by rapid origonally, got the 3.73's installed at ttp who also adjusted his gearing but looked like they didnt hand finish it so thats what i was going to do for him. Heres a scan & the current bin file...as you can see i have it set so it will downshift at anything under 67mph and his upshift is set to 70mph & 6100 rpms...well even from 58-60mph when i go wot it downshifts only to 3rd gear and lays flat on its face...timing seems good although the a/f commanded looks screwy but it still should be downshifting to 2nd gear even if only for a 500 rpm to get rid of his dead spots...also notice that its shifting early...again commanded 6100 rpms but yet its shifting at 5700-5900 rpms. I personally am absolutly stumped at this point as to its tranny shifting issues...anyone with a better clue then me could you please fill me in?

Thanks
Bill

[Jonota]

Bill, did you ever get any resolution on this problem? Long time ago.... BUT, I'm having the same problem on a 98Z. Stock trans and converter, 3.42 rear, head/cammed engine. When I punch it from a stop, sometimes it will shift normally. Other times, with the throttle all the way in, it will upshift to 2nd gear at ~3k. That's annoying enough. But then, trying to do a rolling downshift, it will sometimes shift and sometimes not. When it decides to shift it does it EXACTLY how I want. When it decides not to shift, I can put the throttle to the floor, and MAYBE 5-6 seconds later it will decide to downshift. It's quite annoying.. help?

Jonota

ps. Plan on doing some logging runs for this and to tweak pressures in. What PID's would be best to help illuminate the problem?

[Jonota]

Found some other posts about the TP check found in the Diagnostics. Setting it to Max Kpa 100 and Min Kpa 0 solved my problem completely...

Jonota

[Russ K]

Bill's issue was caused by having the calculated tire dia higher than the current tire dia, the trans shift speeds are based on the trans output revs, not the speedo.

To correct the calculated tire dia; calculated tire dia/current tire dia*trans revolutions/mile. Then close & open the speedo page, the calculated tire dia is now 24.9.

Russ Kemp

[thesubfloor]

Bill's issue was caused by having the calculated tire dia higher than the current tire dia, the trans shift speeds are based on the trans output revs, not the speedo.

To correct the calculated tire dia; calculated tire dia/current tire dia*trans revolutions/mile. Then close & open the speedo page, the calculated tire dia is now 24.9.

Russ Kemp

I have a question about this since I'm having a very similar problem on my 07 Corvette. Although I could understand how how a speedo miscalibration could be responsible for the car not shifting at a certain MPH, I don't think it explains why the car shifts before a certain RPM value.

Unless I'm missing something?

Christopher

[Russ K]

If the WOT shift RPM is lower than the editor, then I raise the WOT shift MPH.

Russ Kemp