automatic transmission does exactly what you want it to do, you may end up loving it as well. After all, if the transmission shifts the same way you would if you were driving a manual trans, we'll, that'd be awesome, and that's what we're going to show you how to do.
The key to tuning your 4L60E transmission properly is defining how you want the vehicle to behave under various driving conditions. The factory programs the Transmission Control Module (TCM) for the "average" driver as well as to make certain the vehicle performs as well as possible during the EPA fuel economy and emissions test cycle and to ensure long-term powertrain reliability. These are excellent goals to be certain, and goals we should only ever try to improve on by adjusting shift strategy based on our own particular driving environment. By installing a new ERod engine and transmission and then adjusting the transmission shift strategy to suit your driving style and environment, you can achieve massive fuel economy savings compared to your old carbureted 350 V8 and 3-speed transmission while enjoying a far more satisfying drive. So, to begin our definition of what we expect from our vehicle, we'll look at the deficiencies of the current TCM programming and decide what we want changed.
One of the worst problems that exists with modern trans shift schedules are the downshifting characteristics. Picture this: You're in 4th gear at 45 mph and you see that you must merge ahead. You dip down into the throttle and the vehicle accelerates s-l-o-w-l-y...You put down more accelerator pedal, and still slow progress. Then more pedal, and as you run out of roadway near the merge and you're finally darned near full throttle, BAM!, the transmission drops down multiple gears and you move out like a scalded rabbit; as if panicked. Is this desirable? I think not. Not to mention that it startles the life out of Granny in the next lane over! No, this simply won't do. Another example is when you make a right-hand turn onto an adjacent roadway from a dead stop. You lean into the throttle to get moving, then hold the throttle as you turn, and then as you straighten out, you add more throttle to accelerate, but the trans has already upshifted and now won't downshift, regardless of throttle pedal setting, and there's a guy coming at you from behind honking his horn. Now, before you say "You shouldn't have turned!", well, try hold that line of reasoning when you live in NYC, or Toronto, Miami, Houston, LA, etc, etc, or any area where traffic gets heavy during rush hour. When you as a driver wish to accelerate, the transmission shouldn't be your enemy. Its very job is to multiply torque and keep the engine in the proper rev-range when you need it to do so! Why the BS? The reason this happens is so that the vehicle in question passes the EPA tests, but it doesn't necessarily help in the real world as you use more throttle for far longer than necessary to make the pass or merge into the appropriate lane or accelerate up to the same speed as traffic. Utter nonsense, and potentially downright unsafe! What we would do in a manual transmission is downshift one gear immediately upon accelerating and only dip partially down into the accelerator pedal, staying in closed-loop fuel strategy (thus saving fuel) and not entering the WOT zone as the above auto trans scenario would have done. So we must adjust the TCM accordingly. Realize, here, that we're not bashing the EPA for their tests or the manufacturers for doing what they can to ensure their vehicles and powertrains pass the tests as well as possible. In fact, we here at Master Engine Tuner and Embex Media support sensible regulation and as our loving elders taught us, "Don't ever tear something down unless you're ready to put up something twice as good in its place." We don't envy the EPA and the hard work they need to do, but when it comes to your hot rod and re-powering it with a modern powertrain, when you know you can do better and make the world a cleaner and safer place, you'd be irresponsible not to. Back down off of our soap-box, let's return to our trans tuning...
The second thing that annoys us is that the transmission doesn't necessarily upshift when we want it to, such as at very low throttle position settings during light-load and low-speed cruising. Why should a 6.2L engine turn at 1,700 rpm during part-throttle cruise when 1,300 rpm will do just fine without lugging? Yeah, we don't know either, so we're going to show you how to change that as well. This little trick, by the way, along with some minor changes to the Torque Converter Clutch settings, bought Dan, our Publisher, an extra 2 days of driving per fuel tank in his 2006 Chevy SSR 6.0L LS2. "Are we sure?" you ask...Yes, we're pretty sure as he drove over 60,000 miles with these very same transmission changes in his truck. He saved a bunch of fuel and the transmission ran far cooler due to the changes we're about to show you. Here's how to get it all done using HP Tuners VCM Suite software:
Once you've downloaded and saved your transmission calibration, open up the Transmission section by selecting Trans in the main menu bar, then Auto Shift Speed in the sub-menu bar. You should see a screen similar to the one below.
If you're like us, you can get pretty sentimental about a car. It's called being an automotive enthusiast, and we love it! And despite what certain government employees may tell you, it's actually pretty green and a more sustainable way of living. Think about all of the materials, energy and resources that go into building a new car. Or, you can simply rebuild what you have and both enjoy your automotive hobby as well as help keep Mother Earth clean. That's what Will did with his 1980 Corvette. He needed an engine and transmission for his beloved Corvette, and instead of rebuilding the tired old carbureted 350 V8 and 3-speed automatic transmission, he decided to install GM's new LS3 ERod engine with a new electronic 4-speed trans. Some enthusiasts love automatics, and some avoid them like the plague. The thing is, if your
On the left above is the WOT Shift Speed compared to the Normal table, and on the right is the WOT Shift RPM compared to the Normal table. It's best to match the two WOT tables so that your shift speed in mph/kph co-relates with the engine speed that would result in that vehicle speed in each gear. This ensures seamless, predictable operation. Also, if you look at both WOT tables, you'll see that in the Speed table, the 3rd to 4th shift is scheduled at 318 mph and in the WOT Shift RPM table the 3rd to 4th shift is scheduled at 8,100 rpm. This obviously means that there will be no 3rd to 4th shift at WOT as the engine will never reach 8,100 rpm (the rev-limiter will kick in) and you won't reach 318 mph unless your name is Thelma or Louise. And even then...
In the top left corner, under Part Throttle Shift, you'll see the table Normal. Click on this table as it's the first one we're going to adjust. The goal here is to modify the shift strategy so that we command the transmission to shift from one gear to another at the vehicle speed that we feel is best for us based on throttle position (and thus pedal position), just as you would when driving a manual transmission. Take a look at our examples below:
In the example above, the original TCM settings are shown followed by our modified settings which are highlighted in red. The last screen-shot shows the difference in the values of the modified cells in blue (aside from the slideshow, you can click the buttons underneath the screenshots to select which photo you wish to view). What we've done here is increased the thresholds at which the TCM will allow a downshift. If you look at the row labelled "2 -> 1 Shift", this row determines the conditions that the TCM will allow a downshift from 2nd gear into 1st gear. As you can see, with a throttle position of between 0 and 75%, the TCM will only allow a downshift below 8 mph. Notice that we've increased the thresholds for the downshifting of all gears, from 4th down to 2nd. What this will now do is allow the transmission to more aggressively downshift gears and keep us from entering WOT when we're accelerating at a moderate pace. At light throttle, less than 31%, we've not adjusted a thing. This makes the vehicle far more enjoyable to drive (as well as safer!) and it prevents you from having to yank back on the shift lever and use the manually-selected low gears, D3, D2, and LOW. Safer? You bet! If you're driving a truck, no more wheel-spin in the rain when towing a trailer and watching the tach spin when the TCM finally downshifts, nor is there any engine braking as there is when using the manually selected gears. In this Corvette, no more wheel-spin when the abrupt downshift hits and 430 hp is sent to the rear wheels! Such abrupt behavior isn't polite in a 98" wheelbase. The best part is that the drivability is now quite predictable and not a silly surprise in heavy traffic as it would be with the stock programming.
Hand-in-hand with the Normal table are the WOT shift tables. You'll see there are two of them. One is Full Throttle Shift Speed (values in mph or kph) and the other is Full Throttle Shift RPM. Adjust these values to match each other as far as vehicle speed vs engine speed. We also like to match them up with the 100% throttle setting in the Normal table as shown below.