am i driving through the converter?
12-11-2004, 03:06 AM
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am i driving through the converter? for starters, the car makes a ton of hp and torque.
when flooring it the car hits the rev limiter at top of third ( th-400) , problem is i'm only going 110 mph when that happens.
i have a PI vigilante convertere set up for a 3000 stall speed, 3.42 gears and 28 inch tires.
could i be driving through the converter or is the tranny slipping, or what.
i done my calculations and the car should be doing ~150 mph when doing 6800 rpm ( assuming the tranny only sees 6200 due to converter slip).
any ideas?
when flooring it the car hits the rev limiter at top of third ( th-400) , problem is i'm only going 110 mph when that happens.
i have a PI vigilante convertere set up for a 3000 stall speed, 3.42 gears and 28 inch tires.
could i be driving through the converter or is the tranny slipping, or what.
i done my calculations and the car should be doing ~150 mph when doing 6800 rpm ( assuming the tranny only sees 6200 due to converter slip).
any ideas?
12-11-2004, 10:05 AM
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Doesn't sound good. We have th400, 3.40 gears, and 28" tire and trap 170mph at 7000rpm. I would say the clutches in the trans are gone. Send the converter back for a refresh when you have the tranny gone through.
12-11-2004, 11:32 PM
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If the 3rd gear clutches were gone, you would not be able to use 3rd gear at all at WOT. It could be the tach is way off, or the torque converter has way to much slip, talk to Terry at Precision Industries. Are these numbers you are giving at the dragstrip?
12-12-2004, 05:20 AM
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thanks for the replies guys.
ok here's an update, apparently all is well!
it turns out the problem was from the speed sensor on the tranny. on ls1 edit you can recallibrate your speedo , but apparently that only fixes the speedo signal but not the signal that the PCM sees. i found that out on the dyno today when we hooked up EFI live and noticed that the VSS signal was reading 158 mph on EFI live when the speedo was reading 70 mph.
it turns out the "rev limiter" i was hitting at 5K was the top speed cutoff due to the PCM seeing a very high reading from the speed sensor.
to fix this problem , i took the speedo callibration back to stock and put in a tire diameter of 10.5 inches. this fixed everything and now the car pulles to 150 mph.
i got to give credit to PI , the converter was setup real good, cause when you floor it on the street it would go up to 5800 ~ 6000 rpm and stay there in the power band while the speed just kept climbing, then the rpm's woulg climb back up to redline.
we double checked if the torque converter was slipping on the dyno by graphing speed vs. rpm and the line was linear with a very slight curve to it ( hard to notice actually) which means there was no slip in the tranny or converter because if there was , the line would by more curved than linear due to the rpms rising while the speed remained constant.
ok here's an update, apparently all is well!
it turns out the problem was from the speed sensor on the tranny. on ls1 edit you can recallibrate your speedo , but apparently that only fixes the speedo signal but not the signal that the PCM sees. i found that out on the dyno today when we hooked up EFI live and noticed that the VSS signal was reading 158 mph on EFI live when the speedo was reading 70 mph.
it turns out the "rev limiter" i was hitting at 5K was the top speed cutoff due to the PCM seeing a very high reading from the speed sensor.
to fix this problem , i took the speedo callibration back to stock and put in a tire diameter of 10.5 inches. this fixed everything and now the car pulles to 150 mph.
i got to give credit to PI , the converter was setup real good, cause when you floor it on the street it would go up to 5800 ~ 6000 rpm and stay there in the power band while the speed just kept climbing, then the rpm's woulg climb back up to redline.
we double checked if the torque converter was slipping on the dyno by graphing speed vs. rpm and the line was linear with a very slight curve to it ( hard to notice actually) which means there was no slip in the tranny or converter because if there was , the line would by more curved than linear due to the rpms rising while the speed remained constant.
