4l60e PWM delete

[east302]

I had the transmission rebuilt on a 1998 Chevrolet K1500 (broken sun shell) and they deleted the PWM and installed a reman torque converter (1611-1654 stall). I don’t know what they used for the delete.

At TCC lockup, how are these PWM deletes supposed to feel compared to the stock configuration? Before being rebuilt, lockup in 4th was more of a change in sound and not necessarily felt like a gear upshift would be. My 98 Tahoe with stock transmission is the same way.

With the rebuild, lockup is a felt “bump” under light throttle. Under moderate throttle, it’s a heavier bump and sometimes feels like it takes two steps to do it - all within maybe a half second. Neither is quite as pronounced compared to a downshift under full throttle, but it’s definitely noticeable.

I called the shop last week, asking the above. He said it was normal operation, but to feel free to drop by and he’d ride along to make sure. I couldn’t get by there until next weekend at the earliest, so in the meantime is this how y’all would expect a PWM delete to behave?

 

[Joseph Garcia]

@NickTransmissions should be able to give you some perspective on this.

 

[Eman85]

The ones I've done when TCC engages depending on throttle position it will feel like another gear that softly engages. It's noticeable on the tach and if you lightly touch the brake pedal enough to turn the brake lights on you can see it disengage, let off of the brake and it will come back on. With a new torque converter it's probably more noticeable.

 

[NickTransmissions]

I had the transmission rebuilt on a 1998 Chevrolet K1500 (broken sun shell) and they deleted the PWM and installed a reman torque converter (1611-1654 stall). I don’t know what they used for the delete.

At TCC lockup, how are these PWM deletes supposed to feel compared to the stock configuration? Before being rebuilt, lockup in 4th was more of a change in sound and not necessarily felt like a gear upshift would be. My 98 Tahoe with stock transmission is the same way.

With the rebuild, lockup is a felt “bump” under light throttle. Under moderate throttle, it’s a heavier bump and sometimes feels like it takes two steps to do it - all within maybe a half second. Neither is quite as pronounced compared to a downshift under full throttle, but it’s definitely noticeable.

I called the shop last week, asking the above. He said it was normal operation, but to feel free to drop by and he’d ride along to make sure. I couldn’t get by there until next weekend at the earliest, so in the meantime is this how y’all would expect a PWM delete to behave?

Your description is text-book for how a converted PWM TCC regulated apply should feel...You def feel your TCC applying and un-locking...That's what you want to feel...GM's PWM TCC's gradual apply basically builds in slip when it's not needed and ultimately results in more stress on the converter clutch. Sounds like it's working as it should.

The 'TCC PWM Delete' is simply accomplished by blocking the TCC isolator valve inboard using a much larger spring or rod to prevent it from moving. Many companies sell such kits, I used them all the time except for when the vehicle has VVT/ACM which needs the PWM active to properly function. That crap didn't start appearing until 2007+ IIRC.

 

[east302]

Thanks, Nick, I appreciate the input. I think it’s definitely a case of me just being used to it driving a certain way and not being familiar with the alternative setup.

So during lockup under heavier throttle, it’s normal for it to have two quick skips or “bump-bump” to it? It’s hard to explain much less type out, but it thumps twice during those times as though it has a quick intermediate step that it’s taking before it engages. I think that’s the engagement that threw me off when I got it.

 

[east302]

The ones I've done when TCC engages depending on throttle position it will feel like another gear that softly engages.

Thanks, I think I was expecting the soft engagement like a gear shift rather than the firmer action.

 

[NickTransmissions]

Thanks, Nick, I appreciate the input. I think it’s definitely a case of me just being used to it driving a certain way and not being familiar with the alternative setup.

So during lockup under heavier throttle, it’s normal for it to have two quick skips or “bump-bump” to it? It’s hard to explain much less type out, but it thumps twice during those times as though it has a quick intermediate step that it’s taking before it engages. I think that’s the engagement that threw me off when I got it.

Not sure what you mean by "skip and bump-bump" but you should feel it applying/locking up (rpms drop by 300 or so) in 4th once you've started to cruise (low throttle angle) and unlocking when you throttle up from cruise to either climb a grade or pass someone but not at WOT. You may or may not feel it unlock when you tap the brakes while in OD.

 

[Marky Dissod]

We all know I ain't NickTransmissions. That said:
Pretty sure precious few people on this forum upgrade the TCC to withstand WOT to improve 1/4Mile trap speeds.

MY UNDERSTANDING of the original reason why the TCC was invented in the first place,
was to improve MpGs in 3rd in 3speeds, and then 3rd and 4th in 4speeds.
Very generally, it likely does not stay locked over 33% TPS.

As for Pulse Width Modulation of the TCC, that's GM trying to improve NVH by making it less blatantly obvious exactly when it locked / unlocked.
NickTransmissions is likely also aware of a non-mechanical way to technically disable PWM of the TCC:
in the tune.
This typically reduces TCC wear as well. However, mechanically deleting PWM of the TCC is never a bad idea -
the client simply must be aware that the TCC operations will be more obviously felt.

 

[NickTransmissions]

As for Pulse Width Modulation of the TCC, that's GM trying to improve NVH by making it less blatantly obvious exactly when it locked / unlocked.
NickTransmissions is likely also aware of a non-mechanical way to technically disable PWM of the TCC:
in the tune.

I believe this is the only real reliable way to do it, though I've heard of folks messing with the TCC regulator valve in the valve body but never did anything like that myself. Most will tune out the TCC apply in 2nd-4th gear and keep it for 5th and 6th so it's working less and generating less heat during stop and go driving that typically happens in 2nd through 4th gear.

 

[Marky Dissod]

Nick, this thread is about the 4L60E, not the 6L80E.
(That said, yes, limiting TCC lockup to 5th & 6th in the 6L80 / 6L90 helps the geartrain last longer.)