Maxie2U

I agree, Tinker was really reaching with his post. To make an assertion the car keeps a complete (100%) log of every AFM transition is ludicrous.

The fact remains as long as you don’t leave it plugged in (or leave it in the car) when you bring it into a GM dealer the Range leaves ZERO foot print.

Tinkertech

Where i work we log almost every parameter available all the time. On chip storage is cheap. This is usually an artifact of the engineering process, a lot of code never gets removed after development just for future analysis. Data is usually stored in very short codes, ie code 35, code 44 etc, which when looked up would refer to a system parameter such as AFM denied, ABS off etc. And this memory would be a loop, overwritten after it becomes full.
So yes they can store a lot of data but someone has to go the extra steps to get to it. Can't be done at the dealership level, must be accomplished in the GM labs with special software and techniques.
With todays processors and ARM chips nothing leaves a ZERO foot print unless the software developer writes the code to do so or not to.

NSC5

If GM was motivated to do so the controller code could be written to look for sustained events preventing AFM from going active and setting a code when this happens but they have not done so. I doubt if this is a priority and for GM the Range module is actually a good thing because it does cut down on transmission issues and does not add stress to the drivetrain like a typical aftermarket tune. GM gets the best of both worlds in having the EPA positive of providing fuel savings technology while allowing customers to easily avoid the downside issues from the system.

Tinkertech

Good point NSC5.
If you use a Diablosport Trinty T2 tuner you can reload your stock tune with the AFM turned off. No other changes except AFM is turned off and no additional stress on drivetrain because this is still basically a stock tune. And using this method you have turned the AFM off the correct way in which the software was designed. You also have the option of monitoring all the parameters if needed.
I do believe if only the AFM is turned off by any means there won't be any warranty issues and you won't be beating on the TC anymore in V4 mode.

MichaelO

Would be nice if you are right about the warranty but I'm not sure about that, like to hear other opinions.

kennyjames21

Can someone explain to me (non-mechanic...) how the v4 mode damages the torque converter?

mountainears

Before someone explains, it should be stated that GM has not stated that it does. There is speculation on this forum that the problem could be caused from the V4 mode. I've seen at least one post from someone on this forum that had an issue who also claimed they never were in V4 mode, but again, that's not science.... It's possible of course that it is a contributing factor, not an actual cause. Hard to really say. IMHO there is nothing definitive, if one is worried about having a failure, keeping it out of V4 mode could possibly be a help.

Personally, I'm not a fan of V4 mode for other reasons, so I choose to run a Range device to eliminate it. If it happens to have an added benefit of easing some stress on downstream components, I'll take that....

NSC5

When a V8 is running on only 4 cylinders it creates much greater vibration and if the torque converter lockup clutch remained engaged constantly this vibration would be transferred to the rest of the drivetrain and the car itself. During V4 operation the lockup clutch is modulated on and off so that the normal fluidic coupling of the torque converter absorbs some of the variation in speed which is what the vibration is in this case.

The lockup clutch is a friction clutch and under normal cruising conditions it remains locked to reduce the power loss (and thus efficiency/economy) loss that occurs in a torque converter that is only fluid coupled. But the constant on/off modulation of this lockup clutch increases wear over time and it will reach the point where it no longer provides the expected "lockup" and the result is slippage and shudder.

The reason the automatic equipped Corvette is allowed to go into AFM in any mode is because GM uses the torque converter to absorb vibration, something that cannot be done with the friction clutch in the manual transmission. If it went into V4 mode under the same frequent conditions as the A8 there would be a high level of complaint about the resulting vibration.

The 8L90 (A8) seems to suffer far more from this issue than the earlier A6 (6L80) and this is probably because when the 8L series was used to replace the 6L it had to fit within the same basic dimensions and GM uses what they refer to as a "squashed" torque converter to save space and apparently part of that squashing reduces the available space for a robust lockup clutch assembly.

One of the diagnostic steps in the original GM TSB for this was to force the engine out of V4 mode to see whether the issue disappeared and this was used to determine if that particular vehicle did have the true shudder issue.

ram_g

Maxie2U

Excellent summary.

Tinkertech

Well said NSC5
Nail on the head
Bravo!

doug doo wop

What is performance shift mode?

Cmud

I had the flush completed with new transmission oil when the car had 12K miles due to the shuddering and rpm fluctuations while in V4 mode. So far so good on that end, no more issues while in V4 mode. Been about 8K miles since I had it done but I am getting another issue.

Now this car used to be my daily driver but for the last year or so I've had the option to drive something else when the weather is bad and when I don't feel like rewashing the vette. LOL So now the vette will sit for extended periods of time, like for a week at the most, just depends on the the weather. So when I drive the vette after its been sitting up it has major problems shifting from 1st to 2nd and from 2nd to 3rd. When it shifts to second there is a pause, almost like it cant shift into the next gear and then it figures it out and slams it into 2nd. It is kind of harsh. When I drive the car daily this problem goes away. Any thoughts?

B-Vette

A fly in the ointment question about The Range vs. using a programmer to shut off AFM:

Isn't it true that having The Range plugged in all the time will kill your battery? Most Forum members have dealt with the dreaded "dead corvette battery," it isn't pleasant. This presents another potential issue to deal with.

Also, having to reach under the dash everytime I want to go for a drive to plug and unplug The Range seems like a pain. Why not just shut it off with a programmer and be done with it? If I go to the dealership for something, I can just dump the stock tune back in when I feel like it.

Johnp94

Updated software on the range afm delete or the newly sold range devices do not drain the battery. My range stays in and I do not have battery issues.

KCV

NSC5

Just use a switched OBD-II extension cable if you have any concerns about the Range unit draining the battery. It isn't a good idea to frequently plug/unplug items into the OBD-II because this sort of usage wasn't anticipated and the connector may wear excessively.

I use this one:

KCV

NSC5

The Z06 is still covered and hibernating through the midwestern winter so I don't have a photo now. I ran the flat cable up from the OBD-II port and tucked it under the lip of the instrument panel trim and then mounted the switch and Range unit high up on the torque tube tunnel using double stick tape (this leaves little residue and what is there cleans up easily from the carpet when removed). The status lights on the Range module are pretty bright so I have mine aimed downward at an angle to the floor so that they can be seen but aren't' creating an inside glare when driving at night.

KCV