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Thread: 4L60E 2-3 Shift Flare Burning 3-4 clutches (Fix)

  1. #1
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    4L60E 2-3 Shift Flare Burning 3-4 clutches (Fix)

    If you have a delay in your shifting or no 2-3 shift on WOT use this attached to check your settings. This will fix the 2-3 lag or no shift that causes the 3-4 clutch burn up.

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  2. #2
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    Can you explain how this works?

    That chart just calculates a VSS signal. In order to complete a 2-3 shift the transmission only needs the shift solenoid de-energized, line pressure boosted before, during, and after the shift.

    If you're bouncing off the rev limiter and it is the tune this may just be an alternative way to correct it, but most 2-3 shift problems I've seen are mechanical.

  3. #3
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    Id like to add to this that if a bad 2-3 shift is happening check Force motor current against actually line pressure via mechanical gauge. If current is dropping and pressure is dropping as well check the force motor aka pressure control solenoid. I found this recently on a Nova with a 4l60e swap and flaring shifts. Found the clutches were smoked then found the force motor was shot and the cause of the whole thing. BTW never threw a single code.

  4. #4
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    So that spreadsheet calculates differently than the hp tuners software? Not sure what you're getting at here?

  5. #5
    Alright guys I'm trying to get this 2-3 flare shift figured out. It's a 00 Vette with a fresh RPM Stage V 4L65E. It was flaring the 2-3 almost 1k rpms before I took it out to send to RPM to get freshened up, I thought this would solve it and it did help but didn't take care of it completely. It still flares 400rpm. Seems to do it worse when its warm also. TJ from RPM said there is no way with the power my car makes it should flare unless something is wrong with tune. Sooooo, I found this thread, but I'm not sure about a couple things. If I use the spreadsheet and plug those numbers in, I get "error" in the Gear/Tire Calc

    If ya'll need more info let me know, just trying to get this problem resolved. Thanks, Kenny
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  6. #6
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    Ran into something very much like this on a 98 fbody that i tuned a few days back would hit limiter no matter what changes i made to shift points or mph finally had to look at a stock 98 a4 file as this car had been tune by someone else before I did. set all vss tables back to stock and the final drive table back to stock then started over on gear change, tire size and shift points no more problem with hitting limiter and trans was shifting within 100 rpms of shift command. Funny thing was I check speedo with a gps when I was having the problem and again after correcting problem it would read the same each time. I have learn more so when going behind someone elses tune if something just does not seem right go back to a stock setting and start over

  7. #7
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    Guys, there is a difference in not shift/ bouncing off the limiter and flaring. Shift problems can very well be caused by variances in shift speed calibration and the speeds in the shift tables. Some trannys are just slow and need a little lead on the mph and rpm. But flares are almost always cause by the tranny builder getting carried away or screwing up somthing in the seperator plate or valve body. I've seen tons of 60's built by old school guys who are used to hogging out holes in the seperater plate to make them shift hard. Flares can also be caused by low fluid, worn out clutches, and to low of line pressure. So all kinds of mechanical problems can cause them. You'd have to really have somthing screwed up in the tune to cause a flare, like completely unrealistic shift / holding pressures or garbled shift tables causing the selected gear to occilate back and forth. If you get a brand new built tranny and its flaring, stand your ground and don't let them blame the the tune, 99% chance its thier screw up. I have had to crutch bad built trannies before with stupid high line pressure. Its easiest to do it accross the board with the force/current table. But if you've got a converted vacumm modualted tranny thats doing it, there is nothing you can do. Send the pos back and get your money back.

  8. #8
    Thanks guys for the replies. It makes the shift without hitting limiter, it just flares it. Another thing I noticed is it don't seem to do it when the trans temp is cold.

    Also got a code today P0751 (1-2 Shift Solenoid Performance) while cruising around. This got me to thinking should I change out the 1-2 and 2-3 shift solenoids? What do ya'll think? Thanks, Kenny

  9. #9
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    For each noid there is electrical and performance codes. The performance code just means the computer sees that its not shifting right. Like taking to long to shift or not moving to the right calced gear ratio. The electrical code pops when it dosen't see an noid on the other end of the wire. Like a broke wire, short, or a burt up noid. I almost always turn off the performance codes on anything with a stall or built tranny.