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Discussion Starter #1
I’m fairly new to the forum, mostly a reader. But recently my truck has started jumping from 50-60 mph. It seems as though it really starts when it shifts into 3rd but I really can’t pin point it. I know that it does it even if I turn O/D off. The last time I unplugged the batteries it reset it and it took a little bit for it to come back. Well batteries died on me so I had to replace them. Well it started immediately. Anyone else have the issue or have advice? Thank you
 

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Welcome. Are you saying that while cruising down the road at 50 it will randomly accelerate to 60 mph? In 3rd? you should not be cruising in third at 50 unless towing heavy. Cruise on or off?
 

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Discussion Starter #5
Welcome. Are you saying that while cruising down the road at 50 it will randomly accelerate to 60 mph? In 3rd? you should not be cruising in third at 50 unless towing heavy. Cruise on or off?


Cruise is turned off. While driving down the road the RPMs will “jump” (like rev’ing the truck at a stand still) causing the truck to “jump” so to say. The speed stays the same and it does not “jump” when accelerating.
 

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Interesting situation, my truck couldn't 'jump' to 50 mph in 3rd let alone 60 mph without leaving transmission and or drive-line parts all over the H'way. Not real clear on your problem but I will sure be following this thread for my edification. Some more info on your truck might be useful.
 

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OK then The ie jumping rpm, not speed. It is called "lockup- issues" If OD is off and in third it is supposed to lockup and stay there e just like in OD during normal driving.

So when you dre jus driving down the road in OD the Torque convertor is unlocking and that casue i tto rev up the lockup again and back an d forth.

This is cause d by AC voltage interference in the system. It comes from a defective rectifier(and/or other parts) in the alternator. The alternator ais putting out over .03v AC and fouling the electronics and actually damaging things like the ECM and others including going in and out of lockup. You need to replace the alternator with one that has less than .03v ac. Napa and Nippon from Napa are not good choices. Bosch or Nations or rebuilding yours with quality parts is necessary.

It can be tested by unplugging the alt and driving it a whild on the batteries and it should stop. Or with a good voltmeter on 2v ac scale not 20 or 200 scale a tteh alt hot wire na case for ground.

Any questions?
 

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Discussion Starter #8
OK then The ie jumping rpm, not speed. It is called "lockup- issues" If OD is off and in third it is supposed to lockup and stay there e just like in OD during normal driving.



So when you dre jus driving down the road in OD the Torque convertor is unlocking and that casue i tto rev up the lockup again and back an d forth.



This is cause d by AC voltage interference in the system. It comes from a defective rectifier(and/or other parts) in the alternator. The alternator ais putting out over .03v AC and fouling the electronics and actually damaging things like the ECM and others including going in and out of lockup. You need to replace the alternator with one that has less than .03v ac. Napa and Nippon from Napa are not good choices. Bosch or Nations or rebuilding yours with quality parts is necessary.



It can be tested by unplugging the alt and driving it a whild on the batteries and it should stop. Or with a good voltmeter on 2v ac scale not 20 or 200 scale a tteh alt hot wire na case for ground.



Any questions?


Thank you! I’m not sure this makes a difference but it does it with OD off and on. I will look at it and do some testing this weekend


Sent from my iPhone using Tapatalk
 

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Yes it will do it in OD or OD off which is 3rd for top gear. It ]does it in whichever gear it top, 3rd or OD(4th) and should be locking up and staying there, but instead unlocks and locks up again, and rinse and repeat.
 
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