4L60e "skipping" 2nd at WOT
06-21-2014, 12:02 PM
#1
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4L60e "skipping" 2nd at WOT Okay, so I've finally broken down and decided to ask if anyone has had a similar issue to mine. About 50% of the time when I'm making a wide open throttle pull from a stop my car will shift into second for around half a second (according to my HP tuners log) and then go straight into third. So it's basically like it's skipping second gear and just going straight into third from first. Sometimes it works and shifts through all gears just fine, sometimes it doesn't. Very inconsistent. I've tried messing with everything I can think of in the tune, I've replaced the valvebody with one from my old trans that had worked just fine, and it still does the same thing. If I leave the shifter in "2" and attempt to force it to go into second that way (from a stop) it hits the limiter in first regardless of how low I set the shift point into second. Second gear feels fine when it actually shifts right, I've made a LOT of second to third gear roll pulls with no issues. Has anyone ever experienced anything like this? Any help/advice/ideas would be greatly appreciated. The car is a 98 Z28 with bolt ons, a cam, 3600 stall, and 4.10s.
Edit: I might add that this transmission has always done this (going on a year now) It also sometimes will try to "launch" itself in second gear.
Edit: I might add that this transmission has always done this (going on a year now) It also sometimes will try to "launch" itself in second gear.
06-21-2014, 09:22 PM
#2
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Since you have HP Tuners I assume you are logging the commanded gear?
If the PCM is almost immediately commanding 3rd gear after 1st gear there is nothing wrong with the trans or valve body, it is just following orders.
I would use the HP Tuners "compare" function to compare my trans tune to a stock tune and make sure all the differences are "logical" and intentional.
Since you probably have already done all these things, it might be a defective PCM. If the problem is intermittent, I would also suspect a sensor problem. Have you tried disconnecting the MAF? Did you tune the VE tables for your cam? You don't want the MAF and VE signals to be widely different as it can confuse the PCM.
Warning - if you have not tuned the VE tables for your cam do NOT try WOT with the MAF disconnected.
If the PCM is almost immediately commanding 3rd gear after 1st gear there is nothing wrong with the trans or valve body, it is just following orders.
I would use the HP Tuners "compare" function to compare my trans tune to a stock tune and make sure all the differences are "logical" and intentional.
Since you probably have already done all these things, it might be a defective PCM. If the problem is intermittent, I would also suspect a sensor problem. Have you tried disconnecting the MAF? Did you tune the VE tables for your cam? You don't want the MAF and VE signals to be widely different as it can confuse the PCM.
Warning - if you have not tuned the VE tables for your cam do NOT try WOT with the MAF disconnected.