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Discussion Starter · #1 · (Edited)
I'm beta testing a 60hp tune and getting an intermittent, quick shudder type problem from the truck at about 75% throttle around the 3-4 and 4-5 shifts, and when accelerating from cruise in 5th to climb a grade. All unloaded driving. I can't tell whether it's a TCC lockup problem or just fishbite in the tune.

The condition begins under acceleration before the 3-4 shift occurs, so at first I didn't think it was a trans issue. It continues through the shift and then goes away for a while once in 4th, begins again during the 4-5 shift. Does it again once in 5th while cruising down the interstate, about 80 mph in cruise control as it pours on the coal to keep speed up a grade.

I've been trying to concentrate on letting the trans learn the new power for the last four or five days. It may have been that I was lifting slightly during those shifts and they got learned wrong. OR, it may just be the tune... Any ideas?

ON EDIT: FYI, the tune has no access whatsoever to the defuel tables in the ECM; all it does is modify the signal to the MAP and fuel rail sensors.
 

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Discussion Starter · #2 ·
UPDATE: The device has a 30hp 'tow tune' also. I bumped it down to this setting and am still getting the same condition. Still does not occur at stock power.

Is there any way for me to rule-out the transmission as the problem? I don't see how a 30hp tune could cause converter lockup problems... But I'm not the first owner of the truck (98k miles now, bought in '05 with 55k), and God knows what abuse it took earlier in its life.
 

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Have you removed whatever it is that you are testing to see if the problem stops?
 

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Discussion Starter · #5 ·
Machinator;1620312; said:
One thing you can do is shift it to Neutral while it's shuttering. If it's still shuttering the problem is in the driveline, if it goes away it may be something in the powertrain.
I'll give that a shot.

RaceHemi;1620651; said:
Have you removed whatever it is that you are testing to see if the problem stops?
Does not occur when I put it back to stock setting.
 
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