Chevy305

Hey so I have a '12 Silverado with the 6.2L and 6L80 that I picked up a few months ago. Within a week of having it I installed a ported 90mm throttle body off of my old LS3 Camaro and an Airaid MIT. Afterwards, I had started to notice that when the converter is locked while cruising around 1200-1800 rpm and applying a little more throttle to accelerate or hold speed on hill that the engine rpm would fluctuate up and down 100-200rpm. The truck would also buck and jerk a bit. I just wrote that off as a lean surge after installing a larger throttle body and intake tube on the factory tune.

However, now after installing a set of headers and getting tuned it seems to be worse. I thought it was a bad tune so I called my tuner and he says its converter slip and its typical for these trucks even stock. He says that he can't do anything more in the tune to keep it from slipping. Some googling and searching has turned up only a few people asking about the same kind of symptoms but no real solutions. What I don't know is if my tuner is full of it (I do trust him, he's well known and good at what he does) or if maybe I'm forced to upgrade the converter. Any advice on this would be appreciated!

01WS6/tamu

iTrader: (36)

It;s the PWM cycling of the converter and is normal. Usually when I tune them set the converter so it cant lock in gears 1-4 at speeds under 45. Even if you leave the shift points alone this will make a dramatic improvment in driveability. What you are describing is the motor lugging its *** off once converter tries to lock at slow around town driving.

FFDP

iTrader: (2)

So you're talking about the Apply/Release Speed Normal table I assume??

So instead of it being allowed to apply at say 20-40% throttle and speeds at 11-15mph for 2nd gear and 17-30 for 3rd gear you just set the speeds to a higher number so it can't lock the converter???

01WS6/tamu

iTrader: (36)

Correct set the tables you mentioned above at 318 MPH for apply and 317 for release. Then I bump of the 5th and 6th tcc apply. But on mine I've tremdously increased the shift points over stock. So with mine it doesn't go into 5th til 53 and then locks the converter at 58. It holds 5th gear until 67 then drops into 6 th and applies converter at 68. Theres a whole host of other things I've done to tweak it to my likes but this will cure your complaint and make the tranny last longer lugging them like the factory does is hell on the converter and hard parts in the tranny it introuduces a ton of stress into the hard parts.

I do all highway driving so it spends very little time in gears other than 6th unless I slow down coming through towns. But I also upped the downshift speeds a good amount so it's not in 6th gear at 45 mph while slowing down from road speed.

After literally a couple years of tune tweak tune tweak I have this 6 speed exactly how gm shoulda done. using 5th and 6th just as double over drives

Chevy305

Thanks for the reply!

So you think its all in the tune? I really hate how the truck lugs sometimes but I also don't want it shifting constantly on me either. Regardless, the bucking and surging with the locked converter happens in almost every gear. I'll have my tuner go back and adjust the converter lock tables and I'll probably have him raise the shift points a hair more.

01WS6/tamu

iTrader: (36)

Change the lock up speeds eliminate lock up on gears 1-4 change 5th 6th gear lock up point
Up the hell out of the upshift and downshift points Keeps it in the right gear and eliminates hunting. Upping the downshift points will prevent it from lugging while slowing down from road speed stock it will hold 6th gear down to almost low 40s if my memory serves me correct.
Reduce the shift timing to speed up the physical shift not the shift point
reduce do not remove TM on the trans side
add a little line pressure.

Turn off tm on engine side
work on your PE delays
lean out your PE table
add some timing
These are the basics and this truck will run day and night difference. As far as the trans tune goes tweak it and drive it tweak it and drive till it finally shifts the way you want it. I despised 6 speed when I first bought this truck and after screwing with it for god knows how long I finally like it. But it took a lot of time. I didn't even like the custom tune I had done when I first got it tuned it made a lot of improvement but took a lot of fine tuning to really make it shine.