I just know the impact of a shift during lockup is really hard on the trans, the converter normally acts as somewhat of a cushion. shifting locked is like shifting a manual without the clutch except the ratios are a lot further apart

 

I noticed that too with my 4L60E that it actually seemed to accelerate faster once the converter locked. Unlocked it was just a sloppy mess and it was the original stock converter too so I don't understand why. Now with my 4L80E and a stock stall diesel converter (1500 rpms) it pulls great locked or unlocked. I actually hit lockup as low as 32 mph in OD and can hold it all the way until 100 mph if I want or I can floor it and unlock and go. Once the throttle is past say 20% the converter is pretty much hydraulicly locked and is nothing more then a shock absorber during the shifts.


I've done that before when I first put the 4L80E in. I pinned the connector like the schematic played it out to be and I ended up having the TCC PWM wire going to the converter clutch solenoid so once I hit 8 mph it was commanding 99% duty cycle or full lockup. It would shift and literally jolt the whole truck and that was with a transgo shift kit too. It had be questioning transgo's sanity until I swapped wires around.

 

All the Bin Files I have seen show the TCC locking at WOT, and at the top of third (other than the 80 which can lock at the top of second). NON of the file allow the tcc to remain locked during a shift, plus the factory allows A LOT of slip in the converter to as Performa said, act as a cushion.

Bottom line, if you are at the limits of your trans power holding ability, locking the converter will only help destroy the trans faster. If you have a 60e you are already at the limit...

 

OK then so the TCC unlocks just before the shift then unlocks immediatley afterwards?

My truck used to lock at the start of 3rd at WOT(it will depend on gearing as lockup is commanded via MPH ), it sucked for the 1/4 mile. I found an extra tenth simply diasbling the WOT lockup. The 2-3 upshift would occur then 1 second later the TCC woudl lock, it woudl kill forward momentum.

Many stock files have the "LOCK TCC DURING SHIFT" box checked. That doesnt mean it actually does however.

Slippage in the TCC is a newer idea(PWM and ECCC), and I agree it does act as a cushion both to the trans and to the driver/passengers.

The 60e shouldnt have been installed in anything larger than an S10.

peace
Hog

 

 

To bring up the old thread ... I've been experimenting more and I think what I am feeling is the TC is slipping when i get on it too hard (above 50% tps). That is atleast what Ithink iam seeing when i monitor TCC slip speed. Is this why i could feel like the truck doesn't accel any faster if i get on it harder? Would the PI 10.5" tripple disc give me the strongest lockup?

 

I asked my tuner at time of tune to command PCM to prevent TCC lockup at WOT(on acceleration). Not quite sure how this works when I'm already on the highway in TCC lockup and I go to WOT. It does feel like the TCC unlocks before it downshifts though. I'm not quite sure because it happens so quickly.