Torque converter lockup cycling
11-24-2005, 08:49 PM
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Torque converter lockup cycling I had a Trailblazer torque converter installed in my '03 5.3 GMC and used Redline ATF. Since the install (1) torque converter won't lock up until 3-4 miles, (2) if lockup occurs before 55 mph rpm will drop about 500 and then after about 2-3 seconds go up about 100 rpm. This appears to be a partial unlocking of the converter (PWM), and (3) if steady throttle is held at any speed between about 45 to 55 mph the rpms begin to cycle on about 2 second intervals. Slightest uphills will stop cycling at the 100 rpm rise and slight down hills will stop cycling at complete lock up.
I am looking for some trouble shooting ideas but would prefer to eliminate the PWM action. Complete 100% lockup when lockup is called for would be ideal.
Thanks
I am looking for some trouble shooting ideas but would prefer to eliminate the PWM action. Complete 100% lockup when lockup is called for would be ideal.
Thanks
11-26-2005, 08:10 AM
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Torque converter lockup cycling.
Originally Posted by Pro Built Automatics
Any of the Trans-Go kits have this PWM eliminator valve, & this should fix this problem.
Thanks. (Now please excuse me while I slink off to my chair and read instructions.) Last edited by Silvrbrd; 11-26-2005 at 08:12 AM. Reason: Font size change.
11-26-2005, 12:47 PM
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O.K. I've read through the instructions. I can't find a reference to PWM. Since everything between the torque converter and the output shaft is MAGIC I wouldn't recognize the parts or a different name. The closest thing I can find is their reference to "Upgraded Isolator & Converter Valve" AKA "ISO-CONV Valve". Could this be it?
11-26-2005, 01:26 PM
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Yes, thats the valve. If you look at the side of the box that has the label, you'll notice it says "PWM Upgrade". Thats the ISO-CONV valve you saw in the instructions.
11-27-2005, 10:31 PM
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My o2 Z-71 was doing the same thing after the tb converter. There is a table you can tune to get rid of this. I have a westers tune and they fixed it right up. The table is called something to the effect of TCC pwm duty cycle. You can have it set up to 98-100% and it will take care of your problems.
