4L80E swap H2 Hummer very sluggish

[SPi]

2003 H2 Hummer, magnuson supercharger, long tubes, mild cam, and meth. This truck has been running on these mods for several years now, runs really strong, 14.1 1/4 mile, with no issues other than the 4L60 it was equipped with would barely last a season. It was decided to do a 4L80 swap this time around. I purchased a conversion harness from PATC . The truck originally had a 12593058 OS, I couldn't find that OS with a 4L80 and ended up swapping everything to a 12613248, it was difficult to find a 1MB file. The truck now runs well and there are no codes but feels unbelievably sluggish. It feels like something is holding it back, you need to use alot of the pedal just to get it moving, you'd swear you were pulling a trailer. Hoping someone can take a look at the tune and shed some light on this for me.

[joecar]

I've been looking at your file a little (sorry I'm a bit swamped at the moment).


Is the engine bogging down, or is the TC not working (stator is freewheeling)...?

Is the PCM cycling up/down thru the gears as you drive (what happens with VSS vs TPS, are you getting upshifts and downshifts)...?

Post some log files.

[Chevy366]

If the TCC is locked it will stall the engine. Look at a stock file with the 4L60e I believe there is a gear ratio difference that might cause the sluggish feel, I see you are running 4.10 rear gear.
4L80e 1) 2.482 -- 4L60e 1) 3.059, Second 4L80e 2) 1.482 -- 4L60e 2) 1.625, Third is the same for both @ 1.000, Fourth 4L80e 4) 0.750 -- 4L60e 4) 0.697.

[SPi]

Thanks for the help guys, I will get some data logs in the morning. I am also going to try a segment swap from the tune in the other thread.

[SPi]

Problem solved ! I was going to do some datalogging but thought I would try a new tune with the file from the other thread. The truck instantly worked better and after just a few tweaks is ready for delivery to my client. Not sure why it never worked correctly on any of the other OS's or segment swaps, but only took one shot using the same OS and is definitely working well. The only thing that will be hard to get used to with this swap is that the 1st and 2nd gears are taller in a 4L80 and the truck has definitely lost some pep off the line, something to consider if anyone is looking at doing this swap. Thanks again for the input guys

[joecar]

Glad it worked,

[joecar]

Yes the 4L80E is closer ratio than the 4L60E, this makes it more suitable for peaky torque rather than wide torque, and can get away with slightly less stall.