Shift points/lock up

[old truck guy]

Tuning seems to be going well but I noticed the other day while cruising about 70-75 down highway that as soon as I hit about 2500 rpm tack starts lunging between about 2400 and 2700 rpm, like its going in and out of lock up. If I slow down below 70 and 2400, it stops. Could this be a ECM/program issue? Truck never did this prior to new motor.

[Fast355]

Tuning seems to be going well but I noticed the other day while cruising about 70-75 down highway that as soon as I hit about 2500 rpm tack starts lunging between about 2400 and 2700 rpm, like its going in and out of lock up. If I slow down below 70 and 2400, it stops. Could this be a ECM/program issue? Truck never did this prior to new motor.

Sounds like you may not have enough hyperstasis between lock and unlock at that TPS/MPH. I would look into using Bluecats transmission software if you don't already. It really helps dial in the transmission tables and takes a lot of guess work out of it.

[old truck guy]

Sounds like you may not have enough hyperstasis between lock and unlock at that TPS/MPH.

Hyperstasis???? Best I can tell this is a medical term. What do you mean?

[Roadknee]

Probably meant hysteresis. For example, if the TC locks at a given tps at 70 mph and unlocks at 60 mph hysteresis would be 10. If the tcc lockup tables were modified and hysteresis were too low the symptom you're experiencing might occur.

[billygraves]

My approach to this.
Assuming oil lvl and no cel is on. I also assume you have not altered the calibration pressures/TC apply release lines via cal nor a resistor across the FM Cir. boosting psi.
Use a scan tool or observe the data via Tuner Pro or other means. Codes set? If yes, address them. No, observe Commanded Gear State, TCC PWM Duty cycle and TCC Slip.
If Gr state does not alter during drive cycle at prob time, observe TCC Slip & TCC D/C. If D/C is steady at this time, observe TCC Slip with the rise and fall or Eng Spd.
If the rise and fall of eng spd follows TCC Slip in 4th, I would follow OEM serv man for diag. Likely Pump or converter fail. If you pull the unit, overhaul it and get it over with. I assume mileage is > 50k also. Use a stacked plate cooler. Place in frt of condenser. Flow and placement for L80. Oil out of trans to cooler, pass to Rad cooler, then External cooler than back to trans unlike 4L60 family.
(In the L80, TCC Slip is actually measuring Engine Spd and Input Spd. This TCC Slip is acutally measuring Converter Cl and 4th Gr cl.) 4th Gr likely hood of failure is much less than the Converter plate slipping. )
Of course I could be wrong. Others that come to mind are TCC PWM Sol is failing.
In L80 boosting line @ 0% TPS will cause converter cl to drag @ Idle. Wear factor increased. I assume U have OEM PCM as well. I suggest you not enlarge pump Pres Reg balance hole with any increase in size. Tests determined this aftermarket increase causes convert whine cold and line pressure to vary over 50PSI with a dampened measurement gu. Gil Younger has, or use to have, you drill a aprox hole in pump (gear side of pump half) aprox 0.035". This increases TCC feed. Connects TCC feed to line pres. Then the TCC Pres spring is exhausting all the time. Results - dragging converter cl - early failure as you have.
It's your $$ and when fails, you get to walk from some mods without complete through knowledge and testing. Some mods may address the immediate prob but long term are not completely thought through well enough in my opinion. I don't know it all and never will.

[old truck guy]

Truck has just over 99k miles. As far as I know, trans is original and untouched, I have no reason not to believe so. Truck is > 8600 gvwr so it has the external cooler in front of the rad already. Made no mods during rebuild, just replaced radiator. Had zero issues with slip or driveability prior to rebuilding the motor so I'm assuming its on the control side. Made quite a few mods to the motor and having a lot of tuning issues, vacuum has changed and I have no idea if my tps voltages are correct. As far as everything else you said, its all French to me. I think im in a little over my head and don't know sh#t about what I'm doing with tuner pro. I need help. I'm on my third bin file from Dave W and some things seem to have gotten better while others worse.