2-3 shift problem
08-21-2010, 04:54 PM
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2-3 shift problem Here is whats going on. I have a built 4L60E trans (shift kit,racing clutchs/kollen steels, upgraded sprag, beast sunshell, Billet accumulator piston, corvette servo,3-4 wide clutch band) with a 3200 FTI stall. I have put around 800miles on the trans. I went to the track recently and when the car shifts from 2nd-3rd gear under WOT it hits the rev limiter for a split second before catching 3rd gear. I tried it on the street and it does the same thing.
My buddy and I tuned it yesterday to try and fix this problem. I have heard that since the 2-3shift is so slow that maybe it was hitting the stock RPM limiter. We up the rev limiter to 6500RPM from the stock 6200RPM. We then took it for a test drive and data logged the runs. The first two passes it shifted 2-3 just fine. On the 3rd pass it did the rev limiter thing again. The data logger showed the car hitting 6200RPM and the fuel injector duty cycle dropping of to nothing. So basically it is cutting the fuel during the 2-3 shift.
I am unsure about what is going on here.
I am wondering if anyone else has experienced this and could help out. The car is a basic bolt on car with a built 10bolt w/3:73 gears. Thanks in advance!!
My buddy and I tuned it yesterday to try and fix this problem. I have heard that since the 2-3shift is so slow that maybe it was hitting the stock RPM limiter. We up the rev limiter to 6500RPM from the stock 6200RPM. We then took it for a test drive and data logged the runs. The first two passes it shifted 2-3 just fine. On the 3rd pass it did the rev limiter thing again. The data logger showed the car hitting 6200RPM and the fuel injector duty cycle dropping of to nothing. So basically it is cutting the fuel during the 2-3 shift.
I am unsure about what is going on here.
I am wondering if anyone else has experienced this and could help out. The car is a basic bolt on car with a built 10bolt w/3:73 gears. Thanks in advance!!
08-23-2010, 10:51 PM
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Tire size and gear ratio is right as far as I know.
08-24-2010, 12:24 PM
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HP Tuners has a bin repository where you can look at peoples tunes and they have a brief description of what they have and what they've done.
I have seen at least two where people say they raised the rev limiter but it was only the one for p/n.
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good to hear.
10-19-2010, 08:01 PM
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How do you raised the cut off RPM. My buddys car is doing the same thing going from 2nd to 3rd shifts. I don't want it happing to my car when Install my 3200/LT's/ORY/373s...
10-20-2010, 11:44 PM
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My buddy and I fixed it by adjusting the Cutoff RPM vs.Gear tab in the Transmission tuning section. It fixed the problem right away and the car runs great now.
10-21-2010, 11:37 AM
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That's because when you put it in D (or 3 on Firebirds), it brings the overrun clutches on which can starve the 3-4 clutches of apply pressure which they desperately need. That's why, IMHO, it's not a good idea to drive it in D or 3 instead of OD, even in city driving, unless you need some engine breaking.
