1-2 shift issue shifting too quick
04-25-2008, 02:36 PM
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1-2 shift issue shifting too quick Rockon 4l60e Trans stage 4... 2800 yank stall.
Last time out at the track the car would A"quick shift" on the 1-2 not even getting to 4500 rpm.. shifting way too early.. 2-3 shift just fine.
Car is also doing one legged burnouts so the "so called factory Limited Slip"
rear is slipping...
Previous trips to the track no issues with 1-2 shift. car normally runs 12.40's to 12.60's could barely get into 12.90's.
Ideas? could it be the rear end fooling the PCM?
Last time out at the track the car would A"quick shift" on the 1-2 not even getting to 4500 rpm.. shifting way too early.. 2-3 shift just fine.
Car is also doing one legged burnouts so the "so called factory Limited Slip"
rear is slipping...
Previous trips to the track no issues with 1-2 shift. car normally runs 12.40's to 12.60's could barely get into 12.90's.
Ideas? could it be the rear end fooling the PCM?
04-25-2008, 06:55 PM
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from what I have heard about Rock-on transmissions I would sugest putting a pressure guage on the unit. You can hit line pressures that will overwhelm the shift valves and flood the selenoids and force the shift.
04-28-2008, 09:00 AM
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Yeah I'm thinking it is the rear diff... screwing with the pcm... need to hook up the laptop and do some data logs.... Now if I can only get her to hook up on the street... hmmmm
Guess I'll throw the MTs on her and see...
04-28-2008, 10:06 AM
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Read your TPS voltage at WOT, a TPS -voltage- in the
fault range seems to produce a short-shift behavior as
some sort of just-in-case. I saw this with TPS reading
4.95V (over-the-top blade angle). Anything over 4.75V
is not "kosher" as far as the PCM is concerned. This is
a "real time" thing, codes require some time-at-error to
set but trans shift meddling is instant.
If traction control is getting to pull back the throttle
that will also short-shift you.
One-wheel peel does not necessarily mean the chunk
is toast, just that the torque bias limit is less than the
wheel-wheel traction difference (which includes right
tire lift and the difference between sliding and static
friction coefficients, the latter can be over 2:1 which
is the stock Torsen split limit roughly. Drive an open
diff for a refresher on what real one-wheel peel is.
fault range seems to produce a short-shift behavior as
some sort of just-in-case. I saw this with TPS reading
4.95V (over-the-top blade angle). Anything over 4.75V
is not "kosher" as far as the PCM is concerned. This is
a "real time" thing, codes require some time-at-error to
set but trans shift meddling is instant.
If traction control is getting to pull back the throttle
that will also short-shift you.
One-wheel peel does not necessarily mean the chunk
is toast, just that the torque bias limit is less than the
wheel-wheel traction difference (which includes right
tire lift and the difference between sliding and static
friction coefficients, the latter can be over 2:1 which
is the stock Torsen split limit roughly. Drive an open
diff for a refresher on what real one-wheel peel is.
04-29-2008, 08:40 AM
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Read your TPS voltage at WOT, a TPS -voltage- in the
fault range seems to produce a short-shift behavior as
some sort of just-in-case. I saw this with TPS reading
4.95V (over-the-top blade angle). Anything over 4.75V
is not "kosher" as far as the PCM is concerned. This is
a "real time" thing, codes require some time-at-error to
set but trans shift meddling is instant.
If traction control is getting to pull back the throttle
that will also short-shift you.
One-wheel peel does not necessarily mean the chunk
is toast, just that the torque bias limit is less than the
wheel-wheel traction difference (which includes right
tire lift and the difference between sliding and static
friction coefficients, the latter can be over 2:1 which
is the stock Torsen split limit roughly. Drive an open
diff for a refresher on what real one-wheel peel is.
fault range seems to produce a short-shift behavior as
some sort of just-in-case. I saw this with TPS reading
4.95V (over-the-top blade angle). Anything over 4.75V
is not "kosher" as far as the PCM is concerned. This is
a "real time" thing, codes require some time-at-error to
set but trans shift meddling is instant.
If traction control is getting to pull back the throttle
that will also short-shift you.
One-wheel peel does not necessarily mean the chunk
is toast, just that the torque bias limit is less than the
wheel-wheel traction difference (which includes right
tire lift and the difference between sliding and static
friction coefficients, the latter can be over 2:1 which
is the stock Torsen split limit roughly. Drive an open
diff for a refresher on what real one-wheel peel is.
I'm just a simple old guy.. grew up on carbs,points, condensers and SBC's. :LOL: Nope.. this is a 3 channel.. no TC on this car..
I don't think the torsen is toasted... but it may be slipping.. she started doing one legger burnouts at the track.. on the street she lights both tires..
She is getting a new eaton soon..
so if I have a voltage error... that may be causing this... what if anything can I do?
Last edited by Sabre; 04-29-2008 at 08:56 AM.
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04-29-2008, 10:22 AM
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Bumpstop mod would allow the blade to travel over center if it it
overdone. Then the TPS will follow it over the top. Just measure
voltage key on, engine off, throttle full open and see if it is above
4.7V.
overdone. Then the TPS will follow it over the top. Just measure
voltage key on, engine off, throttle full open and see if it is above
4.7V.
04-29-2008, 11:14 AM
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05-01-2008, 02:38 PM
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I had a similar issue also, My TB blade was only opening 59 percent and the car thought it was shifting at parial throttle instead of WOT. I will be testing this out tomorrow at the track.
