pwm or non-pwm?? - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

 
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post #1 of 9 (permalink) Old 09-10-2007, 12:07 PM Thread Starter
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pwm or non-pwm??

is there an easy way to tell if my 4r100 transmission is pwm or non-pwm?
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post #2 of 9 (permalink) Old 09-10-2007, 01:47 PM
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Re: pwm or non-pwm??

what does pwm mean?

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post #3 of 9 (permalink) Old 09-10-2007, 03:14 PM
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Re: pwm or non-pwm??

Pulse Width Modulated solenoid.

It is a way to control the solenoid. Earlier transmissions used a solenoid that was 100% off or 100% on. There was no in between. A PWM modulates how much time it is on and off. It can run almost any percentage on vs. off to control the output pressure.

The on/off solenoid was turned on, and the speed of the torque converter clutch apply was controlled by an orifice. The PWM system doesn't have an orifice in the circuit. The PCM controls the duty cycle of the solenoid to control the pressure to control the speed of the torque converter clutch.

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post #4 of 9 (permalink) Old 09-10-2007, 03:40 PM
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Re: pwm or non-pwm??

Utilizing PWM in a program can greatly diminish the snap when the T/C locks up. My current burns are not PWM, and lemme tell ya, it is obvious. Whenever the T/C locks, you know about it.

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post #5 of 9 (permalink) Old 09-10-2015, 12:29 AM
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Is there a way to identify if you have a PWM equipped 4r100? I have 1999 f-250 Superduty with the 6.8 gas engine. I am experiencing a very hard and delayed 2-3 up shift. When I connect my Snapon scanner it does not show the #3 solenoid turn on, but the other two do right before the trans shifts so I'm assuming I have a bad coil pack... Anybody have any input? Thanks!
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post #6 of 9 (permalink) Old 09-10-2015, 06:25 AM
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Only solenoids 1 and 2 are used for shifting. Solenoid 3 controls the coast clutch and is only used when OD is turned off to create engine braking.

Nothing you've said in your post points to a bad solenoid. My guess is that you have a stuck 2-3 accumulator valve in the accumulator body.

To determine if you have a PWM torque converter clutch solenoid measure the resistance of the torque converter clutch solenoid. A PWM solenoid is around 5 ohms while an on/off is around 20 ohms.

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post #7 of 9 (permalink) Old 09-11-2015, 08:16 AM
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Mark,
That the information I was needing, thank you, I will troubleshoot more this weekend, thank you very much!
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post #8 of 9 (permalink) Old 09-14-2015, 01:02 AM
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Thanks again Mark, you were right!

Quote:
Originally Posted by ABurgess View Post
Mark,
That the information I was needing, thank you, I will troubleshoot more this weekend, thank you very much!
Quote:
Originally Posted by Mark Kovalsky View Post
Only solenoids 1 and 2 are used for shifting. Solenoid 3 controls the coast clutch and is only used when OD is turned off to create engine braking.

Nothing you've said in your post points to a bad solenoid. My guess is that you have a stuck 2-3 accumulator valve in the accumulator body.

To determine if you have a PWM torque converter clutch solenoid measure the resistance of the torque converter clutch solenoid. A PWM solenoid is around 5 ohms while an on/off is around 20 ohms.
Mark you were correct, I found two broken (int. clutch accum plunger spring & direct clutch accum plunger spring) and one missing spring ( int. clutch accum regulator valve spring)in the accumulator valve body.
I purchase a Transgo A40D HD-2 and replaced the springs with the ones from the kit and performed all the upgrades but the PWM bypass (everything I could do without pulling transmission). This fixed the hard 2-3 up shift I was experiencing.... But now the transmission shutters when going into reverse. If I hold my foot on the brake in reverse and rev up the engine it doesn't slip and once the rpm's are up the shuttering stops, any thoughts?

On another subject I have seen your post on several other forums and websites, you definitely have helped a lot of people and go above and beyond, it great to know people with your talent and knowledge not only exist but are willing to share and coach people. Thank you!!!!
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post #9 of 9 (permalink) Old 09-14-2015, 06:37 AM
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If the shuddering started since installing the kit I have to suspect something in the kit caused it.

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