Some good info here. I'll guess I'll chime in since I've had that switch on my truck for about 5yrs. I only lock mine at 35mph+ because any lower and it sounds like the truck is really struggling in that gear (2nd or 3rd? must be third...). The only reason I use mine is my PCM is burned NAW6, not TDE1 (need to have it reflashed, or buy a chip), so the T/C doesn't lock until right before the OD shift, which can be annoying on windy back roads in the area with a 40mph limit. I usually lock the T/C at 35, then lockout the OD, that way the truck stays in 3rd with a locked T/C, and I can use just the throttle pedal to regulate speed.

Did I mention I wish my truck was a standard?

ALSO do not use the switch after a few beers... you will forget that it's locked and almost stall the truck... woops!

 

So is this mod still effective if I have a chip?

 

Mike, yes it still is effective. Just depends on what you use the lock for. Most couple it with an exhaust brake (usually by modding the EBPV) so you can actually utilize the stopping force. Personally, I use mine to get the T/C locked earlier than my PCM tells it to to get my rev's down when cruising in town. Most chips are burned TDE0 or E1 that have a better shift strategy, and get that T/C locked much earlier.

Long answer so short question... it will still work and is a cheap/free mod

 

Thanks Robb, I've got the Decel Tune from DP and have heard good things about it from the SD Guys. Should eleminate the need for the EBPV Mod (I know its cheap than a Tune) and at $45 it was worth checking out.

So the TC adjusts the shift points in the Tranny? Unclear on what the Mod affects/does but lower Trans temps are always needed when towing in the Cali deserts!!

 

No, no. Sorry if I was unclear of that. I guess I assumed everyone knows what the T/C does and how it works. When unlocked, your TC is constantly "slipping" some, so you can't transfer all of the engines power to the transmission. This is essentially what allows you to stop and not stall, as one side of the TC is spinning and the other is stationary.

The Locking portion of the TC "locks" both "halves" together, giving 100% power transfer from the engine to trans. The PCM controls when this lock happens. With different PCM programing, the lock will occur at different throttle inputs, RPM's and speeds. This is why my NAW6 PCM locks it at 45mph, and the TDE1 PCM locks at 35-40mph iirc (3.55 gears)

The TC does not directly impact the transmission shift points, but could in itself be thought of as a "shift" going from a locked to unlocked state and vice-versa

Much more info on TC's HowStuffWorks "How Torque Converters Work"

Hopefully that helps some. Let me know if you are still unclear. Take a look at the above, does a good job of explaining TC and has some nice diagrams. The lock is explained on one of the pages also

 

I find that if I lock mine just before it shifts to 2nd gear it pulls great after that. Otherwise I wait till about 35mph or so like Robb.

Mine does the same thing where it doesn't lock till about 45mph or OD. So annoying, it feels like the transmission is shifting 7 times before it hits OD and it's only a 4-speed trans...

Can't wait to get my ZF5 swap done...

 

Evan, I know exactly how you feel about the trans taking forever to get into OD. Plus the 3rd to od shift is so sloppy because the TC locks RIGHT before the OD shift, unless you are in the throttle. Embarrassing riding around with others...

I'd be willing to bet you have a NAW_ PCM code like I do. The TDE1 is much more forgiving, but I'm not paying $150 for my local dealer to re-flash it. When I have the time (and money) she'll get the hand-shaker conversion also