94 Camaro shifting problem

[Ken Kelly]

Jim,
	The other posters are correct. The PCM tells the Trans when
to shift. Trying to locate what the problem is requires time
sorting the mod list to understand when it started.

	As I understand it the problem started when you shifted to
3.73 gears. This would cause the problems you describe if
the PCM wasn't properly reprogrammed. The early HPP did have
problems with 4.10 gears, don't know if it applied to 3.73.
When you took it to someone with the TTS did they start with
a fresh copy of 16209471, or did they try to fix the
existing PCM firmware? If the HPP scrogged a table in the
PCM, he may have not caught it with the mastertune software.
I just finish writing software to do the gear scaling. To
change from a 2.73 to a 3.73 gear ratio in the 16188051, I
scale over 1000 bytes of data in the PCM. It is a really
complex and major change that effects both processors. The
transmission shift tables are stored in the PCM in MPH
units. They really should have been stored in output shaft
revolutions. Since they are in MPH all the tables have to be
rebuilt to rflect the new shift speeds.

		Ken

Jim Sloan wrote:
> 
> I have been helping a friend with a 94 Camaro Z28. It has a highly modded
> 355 LT1 that is fed by an ATI procharger and N2O. It does not shift gears at
> WOT. He has used a Hypertech power programmer to adjust the shift
> points, but it doesn't seem to make a difference. It always goes to the rev
> limiter (wherever it is set).  On part throttle driving, the tranny shifts
> normally.  After talking to the guys at Hypertech, he sent the unit back to
> have a new chip installed.  That did not work either. Then he went to a
> custom tuner who uses MasterTune but could still not fix this problem.
> He recently had the transmission rebuilt.  It is a 4L60E with a TransGo
> shift kit, larger 2/4 band, mechanical diode, etc etc.  This problem
> occurred before the motor and the tranny were built also.  At the same
> time, he switched from a 2.73 to a 3.73 gear. They have not been able to get
> it to shift at WOT, either.
> TCC doesn't engage until around 80 mph even with the program set to lock up
> much earlier.
> 
> It seems to run very strong, otherwise.
> 
> Can anyone offer some suggestions on this? Anything in the prom we may be
> overlooking?
> 
> Thanks in advance.
> 
> Jim Sloan
> leroy at sunflower.com