First time at the track no 2-3rd shift
08-07-2014, 10:26 AM
#1
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First time at the track no 2-3rd shift Took my bolt on Trans am to the track for the first time last night went, to lebanon valley in new york. Mods for the car are Lid,exhaust, built tranny, 4500 stall. Car left really good shifted 1st to second fine then when it went to shift into 3rd it just bounced off the limiter 4-5 times. I tried leaving it in 3 rather than drive and it did the same thing
Fearing that i killed the tranny i packed up for the night and headed home, just for ***** give her hell from a stop light and it shifts perfect with no issues. Now this is the first time i have had any problems with it, on the street it has run flawless, then once on the track it wont shift any idea? Im thinking its in the tune and i need to readjust my 2nd to 3rd mph/rpm points.
It did go 12.7 at 106 with a 1.7 60 foot with it refusing to shift into 3rd.
Fearing that i killed the tranny i packed up for the night and headed home, just for ***** give her hell from a stop light and it shifts perfect with no issues. Now this is the first time i have had any problems with it, on the street it has run flawless, then once on the track it wont shift any idea? Im thinking its in the tune and i need to readjust my 2nd to 3rd mph/rpm points.
It did go 12.7 at 106 with a 1.7 60 foot with it refusing to shift into 3rd.
Last edited by dirkdiggler350; 08-07-2014 at 02:25 PM.
08-07-2014, 12:19 PM
#2
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If you have easy access to tuning I would start by reducing the 2-3 shift MPH by 5% or so.
Was it ever tuned for the high stall?
Just idling in the staging lanes, especially on a hot day, will raise all temps including the transmission temp. I have measured that trans line pressure is slightly lower as the temperature goes up. Lower line pressure will cause a bit more slippage on shifts.
Here is my hypothesis: the high temps at the track are causing a bit more slippage than during normal driving. Hence it shifts perfectly normally but hits the rev limiter at the track.
For anyone during track runs I recommend either the full Transgo or Sonnax shift kit or at least a bigger boost valve. The bigger boost valve will raise line pressure across the board (with the same tune) and give a slightly higher maximum line pressure. The Sonnax 4L60-LB1 boost valve costs about $25 and is easily installed after taking off only the pan and filter.
Was it ever tuned for the high stall?
Just idling in the staging lanes, especially on a hot day, will raise all temps including the transmission temp. I have measured that trans line pressure is slightly lower as the temperature goes up. Lower line pressure will cause a bit more slippage on shifts.
Here is my hypothesis: the high temps at the track are causing a bit more slippage than during normal driving. Hence it shifts perfectly normally but hits the rev limiter at the track.
For anyone during track runs I recommend either the full Transgo or Sonnax shift kit or at least a bigger boost valve. The bigger boost valve will raise line pressure across the board (with the same tune) and give a slightly higher maximum line pressure. The Sonnax 4L60-LB1 boost valve costs about $25 and is easily installed after taking off only the pan and filter.
08-07-2014, 12:48 PM
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It has a frost mail order tune that he tuned for the stall, a buddy of mine has hp tuners so i will try to adjust the mph down and see if that helps. As far as the the shift kit it has a trans go hd-2 in it when it was rebuilt but im gonna look into the boost valve also.
08-07-2014, 02:14 PM
#4
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All sounds good then. The HD-2 includes a boost valve.
I would try reducing the 2-3 shift MPH down then.
Keep in mind that even though your friend has HP Tuners it will cost him $100 (2 credits) to change another PCM. Of course he can then change your PCM as many times as you want without additional charges.
I would try reducing the 2-3 shift MPH down then.
Keep in mind that even though your friend has HP Tuners it will cost him $100 (2 credits) to change another PCM. Of course he can then change your PCM as many times as you want without additional charges.
08-07-2014, 02:24 PM
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Ya i know im gonna have to give him some money for the credits, now should i only change the mph and leave the rpm the same or should i scale both down the same percentage.
08-07-2014, 02:44 PM
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Thing is the transmission is brand new only put about 600 miles on it, so im 99% sure it has to be in the tune. Weird thing tho is on the street it shifts perfect, i can hot lap the crap out of it on the street and its fine but 1 pass on the track and it wont shift.
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08-07-2014, 02:55 PM
#8
Try lowering the MPH points but you might need to widen the gap between where shifts are happening and the engine rev limit.
For example: if it's shifting at 6500, set the rev limit to no less than 6800 (and raise fuel re-enable the same amount). I had a similar problem before. For some reason the car runs a little different at the track than on the street. My guess is either the same things mrvedit mentioned or the sticky track prevents tire slip on the 1-2 shift and builds slightly more MPH by the time the 2-3 is going to occur.
For example: if it's shifting at 6500, set the rev limit to no less than 6800 (and raise fuel re-enable the same amount). I had a similar problem before. For some reason the car runs a little different at the track than on the street. My guess is either the same things mrvedit mentioned or the sticky track prevents tire slip on the 1-2 shift and builds slightly more MPH by the time the 2-3 is going to occur.
08-07-2014, 02:55 PM
#9
Try lowering the MPH points but you might need to widen the gap between where shifts are happening and the engine rev limit.
For example: if it's shifting at 6500, set the rev limit to no less than 6800 (and raise fuel re-enable the same amount). I had a similar problem before. For some reason the car runs a little different at the track than on the street. My guess is either the same things mrvedit mentioned or the sticky track prevents tire slip on the 1-2 shift and builds slightly more MPH by the time the 2-3 is going to occur.
For example: if it's shifting at 6500, set the rev limit to no less than 6800 (and raise fuel re-enable the same amount). I had a similar problem before. For some reason the car runs a little different at the track than on the street. My guess is either the same things mrvedit mentioned or the sticky track prevents tire slip on the 1-2 shift and builds slightly more MPH by the time the 2-3 is going to occur.
08-07-2014, 04:30 PM
#11
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When less than WOT, the shifting is done only by the part-throttle MPH table (even though the table goes up to 100% throttle). There is a value which determines what "WOT" is, the default is somewhere around 98% but I have mine set to 95%.
Now for WOT, there is a "Full Speed Shift Speed" table and a "Full Throttle Shift RPM" table. (Actually "Normal", "Performance" and "Hot" tables of each.)
When WOT is true, **BOTH** the tuned speed **AND** the tuned RPM must be reached before the shift takes place. If either is too high, you will hit the rev limiter.
Here is what I do. I set my WOT shift MPH to correspond to about 6200 RPM or 10% less than I normally shift at. Then I set my WOT Shift RPM to exactly what I want.
At the track I then only need to change my WOT Shift RPM table to experiment.
(Note I have my rev limit set to 7050 and you therefore may need to adjust accordingly.)
Minor detail: with my '98 PCM the trans shifted exactly at the RPM I set in the WOT Shift RPM table. However my '02 PCM seems to assume some slippage and shift about 200 rpm less than my WOT Shift RPM table. Therefore I set the WOT Shift RPM at 7100 when I want it to shift at 6900.
(My trans is built for very fast shifts.)
To answer your questions, as long as your WOT Shift RPM is a little less than your rev limit, I would only change the WOT Shift MPH. Don't bother with 1% or 2%; lower it by 5%.
(I have heard of people setting their WOT Shift MPH to 0, but that seems to confuse at least '99+ PCMs.)
Now for WOT, there is a "Full Speed Shift Speed" table and a "Full Throttle Shift RPM" table. (Actually "Normal", "Performance" and "Hot" tables of each.)
When WOT is true, **BOTH** the tuned speed **AND** the tuned RPM must be reached before the shift takes place. If either is too high, you will hit the rev limiter.
Here is what I do. I set my WOT shift MPH to correspond to about 6200 RPM or 10% less than I normally shift at. Then I set my WOT Shift RPM to exactly what I want.
At the track I then only need to change my WOT Shift RPM table to experiment.
(Note I have my rev limit set to 7050 and you therefore may need to adjust accordingly.)
Minor detail: with my '98 PCM the trans shifted exactly at the RPM I set in the WOT Shift RPM table. However my '02 PCM seems to assume some slippage and shift about 200 rpm less than my WOT Shift RPM table. Therefore I set the WOT Shift RPM at 7100 when I want it to shift at 6900.
(My trans is built for very fast shifts.)
To answer your questions, as long as your WOT Shift RPM is a little less than your rev limit, I would only change the WOT Shift MPH. Don't bother with 1% or 2%; lower it by 5%.
(I have heard of people setting their WOT Shift MPH to 0, but that seems to confuse at least '99+ PCMs.)
08-08-2014, 09:20 PM
#13
slightly over filling fluid has been rumored on here to help the 2/3 rev limiter condition especially if gear selector is in OD , typically it wont happen on the street but will at the track like your describing seen it discussed many times , maybe launching on sticky tires is forcing more fluid rearward in the pan or trans than on street tires ?
