Help w/ strange TC/Shift issue with Fuel Sipper tune

[cleatus12r]

Originally Posted by soutthpaw

I have ran the fuel sipper for a couple days now and its good except it does a strange shift hunting thing at light throttle around 40MPH it shfits up/down/up/down a few times... esp when cruise control is set.. I looked at the up and down shift points in FUNCTIONS and they are way lower than the range it is shifting at... does it with warm and cold tranny... Is there another map or parameter I should look at to adjust. I thought it was a 3-4 4-3 shift issue but I briefly had a chanve to run the AE on it and it looks like the TC is locking and unlocking repeatedly and can't settle on where it wants to be(while its in OD). I notice the 100HP tune has a similar shift curve but slightly higher (about 6mph) so I'm gonna try and see if it still does it using cruise in the 100HP tune...
is the 3-4/4-3 shift with (cruise) labeled like that specific for tuning the cruise control shift points??? it seems logical but I already found out that doesn't mean its correct I really need some time without my kids in the truck to run the AE software as well to see what its really doing... so I can see the throttle position when it does these shifts/ TC lock/unlock... I don't recall the 80HP having that issue though I replaced the 80m spot with the FS tune...
It also seems to lock the TC kind of hard like someone has a tow strap attached and giving it a tug when the TC locks. I can't seem to find what parameter is different from the 80 HP tune so not sure what to try changing

DJ,

I'm going to run this tune first thing in the morning. I have spent a while looking at it. I assume you changed the tire size to 601 Rev/mile to lower the PCM's perceived road speed. In addition, you should NEVER have a condition when you're in 4th gear and the torque converter is unlocked unless the PCM is in cold transmission mode. The PCM will command a 4-3 downshift and subsequent TC unlock/relock (and the faster that happens, the better).

Your TC lockup points are unchanged...while the upshift speeds are lowered 2-4 MPH. This might be an issue....and it's going to be exaggerated with different vehicles, elevation, and state of tune.

Your TC harsh lockup is caused by a higher-than-stock lockup duty cycle. Remember, we have a PWM TCC solenoid...the higher the duty cycle during lockup, the more it becomes like an on/off solenoid. The second issue is the torque table...I feel it's a little high in the low load section of the table. The higher the torque table values, the harder EVERYTHING is going to apply. It's just a personal preference of mine to lower the values in the torque reduction during shifts as well. I see that most folks like to run 100% torque during shifts. I prefer about 62-75%.....I call it my tranny saver. I command a quick, firm shift but I never feel it happen.


I'll drive around tomorrow and see what I can see.

A couple suggestions...lower the torque table values in the lower loads by 100-150 ft. lbs. or so.

Lower the TCC lockup duty cycle back to near stock....maybe just slightly higher.

Run a slightly different change in each of your 6 positions and find the one that works the best.


I'll let you know what I come up with on the shifting/TCC issue you're having.

You do know how to quickly copy and paste table data from one project to another don't you? It's a lifesaver while loading stock data back to a modified table.