trans kind of slipping after h/c install?
08-03-2004, 03:22 AM
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trans kind of slipping after h/c install? The trans was fine at first after h/c install. Now after a change in the tune to adjust shift pressure for 3rd gear, it seems to slip. This only happens at past 1/8th throttle but before 3/4 throttle. It seems to be delaying or something when going to 3rd. Anyone got any ideas? Is it the tune or the cam?
Thanks
Thanks
08-03-2004, 08:27 AM
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This could be the converter clutch, that seems
like the weakest piece on mine.
What table(s) did you edit? There's shift pressure
(which should only affect the shift actuation) and
there's the line pressure vs load vs temp table.
The line pressure table, "less is more" - it's a blowoff
sort of pressure reg and more current = less pressure.
Log your TCC duty, TCC slip, PWM line and any trans
shaft speeds and you should be able to see where the
slip comes, and why.
You might want to go back to the original tables as
soon as possible, because slip under moderate load
seems to be a good way to glaze things up and
put a hurt.
like the weakest piece on mine.
What table(s) did you edit? There's shift pressure
(which should only affect the shift actuation) and
there's the line pressure vs load vs temp table.
The line pressure table, "less is more" - it's a blowoff
sort of pressure reg and more current = less pressure.
Log your TCC duty, TCC slip, PWM line and any trans
shaft speeds and you should be able to see where the
slip comes, and why.
You might want to go back to the original tables as
soon as possible, because slip under moderate load
seems to be a good way to glaze things up and
put a hurt.
08-04-2004, 09:33 AM
#4
It can also be the T/C seeing the misfires from the the cam and not letting the clutch lock up. Make sure you disabled code 300 and changed the idle and low misfire detection counts to 32767.
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08-05-2004, 08:58 AM
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Knocking down the adaptation times was enough for
me to get good firm shifts. However this is a "soft"
setting (a PCM learn goal, not a direct change to
pressure) and maybe you want to up the shift
pressure setting as well, if you haven't.
Depending on where you feel this "softness" issue
(in terms of load/throttle position), you may want to
start shaving on the force motor table to fatten up
the low-load line pressure. This table indexes with
"commanded line pressure" & temperature. Commanded
line pressure follows delivered torque. With an
aftermarket converter there is more torque delivered
to the input shaft than the PCM "thinks" (it having
some "model" of the low stall, low STR stock converter
to convert the engine shaft torque to transmission
input shaft torque). Anyway, if you log the line PWM
% PID and find the "sweet spot" (or not so sweet) of
the slippage / softness, you could go into the
Force Motor table and start reducing current about
that point, bit by bit, until the holding power is
preventing slip.
At part throttle the commanded line pressure is
driven by delivered torque / load and this all comes
off engine airflow / cylinder charge calcs the way I
understand it. There's a good chance that the heads
& cam have improved output per airflow as well as
raw airflow ability. If the MAF table was edited as
part of tune (to lean out) this would pull off some
trans pressure at part load. So far I have not seen
the direct load - line pressure mapping table made
accessible in HPTuners but the next layer (commanded
line to force motor) is there and can suffice.
me to get good firm shifts. However this is a "soft"
setting (a PCM learn goal, not a direct change to
pressure) and maybe you want to up the shift
pressure setting as well, if you haven't.
Depending on where you feel this "softness" issue
(in terms of load/throttle position), you may want to
start shaving on the force motor table to fatten up
the low-load line pressure. This table indexes with
"commanded line pressure" & temperature. Commanded
line pressure follows delivered torque. With an
aftermarket converter there is more torque delivered
to the input shaft than the PCM "thinks" (it having
some "model" of the low stall, low STR stock converter
to convert the engine shaft torque to transmission
input shaft torque). Anyway, if you log the line PWM
% PID and find the "sweet spot" (or not so sweet) of
the slippage / softness, you could go into the
Force Motor table and start reducing current about
that point, bit by bit, until the holding power is
preventing slip.
At part throttle the commanded line pressure is
driven by delivered torque / load and this all comes
off engine airflow / cylinder charge calcs the way I
understand it. There's a good chance that the heads
& cam have improved output per airflow as well as
raw airflow ability. If the MAF table was edited as
part of tune (to lean out) this would pull off some
trans pressure at part load. So far I have not seen
the direct load - line pressure mapping table made
accessible in HPTuners but the next layer (commanded
line to force motor) is there and can suffice.
