68rfe 6th gear shift not following shift map? What am I missing?

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Attached is the current file that is in my truck and a data log of it shifting. if you follow the shifting for 6th gear, it looks like it is shifting 500 rpms (output shaft speed) later than it should. when it actually shifts to 6th at 35.7% accelerator pedal position it is at 2841 OSS. It shouldn't shift at that rpm unless its at about 85% TPS. At 35.7% it should be shifting between 2270 and 2280 OSS.

Looking at the log, it should have shifted at about 40% throttle around 2302 OSS. Instead I had to lift the throttle slightly to trigger an upshift. One thing I noticed, not sure if it plays any role in the shifting pattern though, is that it doesn't seem to shift until the calculated trans torque is at or below 300 ft lbs? is that just a coincident or does it play a role in shifting? Do I need to do something different with Tq Management?

I did change the throttle interpret a few tunes ago because I wanted to know when I was at 70 or 80 or whatever %, that I was actually at that %, instead of me thinking I'm at 40% and it thinks its a 60 or 70%.


Any ideas on what I might be missing would be helpful.
Thanks!

[Jim P]

FYI, if you change the throttle interpretation table you are messing with a whole lot of things with just one table. That table converts the actual throttle position to an angle that is used in a mass multitude of things.

[Jim P]

Your downshift rpm at 57.3% throttle and 71.4% throttle is set higher than your upshift point... This will cause issues.

[Jim P]

Just one more thing to add, HP Tuners has the throttle interpretation table messed up on ALL 68RFE equipped trucks. Not a major, it?s just shorter in the HP Tuner software than it actually is in the calibration files.

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Thanks for the help Jim P. I changed the throttle inter back to what it was stock and corrected the overlap on the upshift/downshift. no change in behavior. I'm almost at the point of changing the axis values back to stock as well to see what that does. It's just weird that all other gears shift fine and when I want, but not 6th.

[Jim P]

Do you have a stock readout that you can post up?

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Do you have a stock readout that you can post up?

[Jim P]

Curious why you would max out pressure gains. I can tell you that HP Tuners has some incorrect mapping on the pressure gains/gear table. What they have as the pressure gain for 6th gear is actually the pressure gain for reverse and what they have for reverse pressure gain is actually neutral pressure gain. They gotta step up their game.

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I have an upgraded valve body/ separator plate and was planning on tuning the motor for above 500hp at some point. In order to try getting the 68 to be happy with that, I've read in multiple places (some of it here) that increasing the line psi can help prevent the clutches from slipping when you are increasing power. I wanted to have it come up as quick as possible when getting in the throttle, that is the reason for the increase of pressure gains. If that is not a good idea, I'm happy to change it back to a better setting....? I was somewhat following the "guide" that is on the forum too.

[Jim P]

Yea don?t follow the guide on this forum, it?s no good. Yes if you got an upgraded valve body you can run higher pressures to hold your clutches together, I wouldn?t set pressure gains to max though, plus they got the mapping of the gains kinda messed up anyways. I would run your gear gains at 0.49 for the forward gears. Not necessary to be so aggressive with the gains that the moment you touch the pedal you jump to max pressure. I would use the shift duty cycles to fine tune the hand off between clutches during shifts.

[Jim P]

As for your WOT shifting, look back at the stock shift scheduling and note what they are doing with the oss speed and throttle position, I would recommend following a similar style pattern. For example on my 2012 I currently have my 5-6 shift set as 0, 16.1, 32.2, 48.2, 64.3, 80.4, 96.5, 96.5 for throttle position and 1888, 1888, 2304, 2752, 3168, 3616, 3936, 3936 for the oss speed.

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As for your WOT shifting, look back at the stock shift scheduling and note what they are doing with the oss speed and throttle position, I would recommend following a similar style pattern. For example on my 2012 I currently have my 5-6 shift set as 0, 16.1, 32.2, 48.2, 64.3, 80.4, 96.5, 96.5 for throttle position and 1888, 1888, 2304, 2752, 3168, 3616, 3936, 3936 for the oss speed.

12 68rfe shift pattern.PNG on the 12's, they go all the way to 100%. is there a reason why you cut it off at 96?

6th shift numbers.PNG6th shift map.PNG attached are what my shift map looks like graphed out for my gear and tire size. it will show what mph (roughly) it should shift at with the converter locked.

[Jim P]

Yes they have it up to 100 but look at it closer what they are doing with the position and the oss. Everything above a certain throttle angle or 96.5 percent throttle is considered WOT, where WOT targets get used, so the top end of each shift I have set down to that threshold with target engine rpm set to match up with the shift tables. Converter locked or unlocked for shifts is irrelevant as it based off of throttle and output shaft speed, output shaft speed doesn?t change because the the converter locks or unlocks.

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I think I'm missing where you are getting 96.5.... I see what you are saying about above a certain throttle angle it is considered WOT(I think). On my stock file, on every upshift but 6th, anything over 52.2% throttle had the same value as 100%. In 6th, 44% was the same as WOT.

you are right on the the converter being locked or unlocked making no difference on what MPH it shifts at, only what the engine RPM would be if it were locked vs unlocked. That's what I was thinking in my head but I should have said it different.

[Jim P]

I think I'm missing where you are getting 96.5....

On the 2012, think it's a bit different on the earlier 68RFE's, I'd have to do some more digging, but as far as the transmission goes there is a bunch of parameters that use throttle angle, not throttle percent, and everything between 0-96.5% throttle is the "part throttle" range, the 96.5% throttle is the equivalent of the set WOT throttle angle in the transmission calibration. The WOT throttle angle parameter is not mapped out. As far as I am aware, there isn't any offsets or anything to cause a 500rpm late shift in any specific gear or throttle range, mainly boils down to how the ECM/TCM uses the tables. There are some delays and stuff in there, most are pretty minute.

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is one of those delays waiting for 5th to lockup the tcc? I have noticed that it will not shift to 6th unlocked. it has to lock up 5th and then will shift. which bring me to my next question, how can I get 5th to lock up under heavy load/throttle? I can change to tcc tables and the limits but it doesn't seem to follow...

[Jim P]

I haven?t had any opportunity to hook up to a 2007.5-2009 68RFE but can 100% confirm that every platform, other than EZ Lynk, that offers tuning capability on the 68RFE, has the throttle axis of the shift and lockup tables wrong, at least on the 2010+ 68RFE. Like I said, haven?t had any opportunity to hook up to a 2007.5-2009. The correct throttle axis is throttle angle in degrees.