47re down shift & converter unlock

[jlbayes]

Ok this is driving me nuts. On my 97 if you use heavy throttle it will down shift from overdrive & unlock the converter even with switches for both to force lockup & overdrive. I did replace the tps with a tps delete with no change. What does not make sense to me is it will do it regardless of the switches. Yes there is a jumper harness for the trans relay in the pdc under hood. It does have an old school dtt voltage box from a previous owner that I am thinking is going to take a permanent vacation. Truck is all stock, no power mods. Previous owner had recently replaced the electronics in the transmission. Switches are tied into the harness near the pcm.

[pepsi71ocean]

Try unplugging the alternator and see if the issue goes away, may need to run a potential meter otherwise.

[jlbayes]

I'll give that a shot. 

[CSM]

I am not an expert in the 12v.  
 

That said.  

 

I have been chasing my converter for a long time.  Mine comes, goes, and seems like my truck is a union truck. If I don't drive it much, it shifts perfectly.  If I drive it daily, about a month in, it starts to shuttle.  

 

I found improvements in cleaning or replacing grounds, replacing alternator that was way out of VAC spec. I also found improvment for a short time by cleaning my transmission output speed sensor.  

 

Beyond that, I haven't figured it out. It seems to be worse at high ambient temperature. Above 60F it gets more common to almost constant at 100F when I am driving at less than 65mph.  Above 65, I don't see any issues. 

[jlbayes]

Being as I am newerish around here care to describe what yours is acting like?

[CSM]

I have done the procedure here.  http://www.dodgecumminsapps.com/page04.html

 

My truck normally shifts great.  Once in a while, usually in hot weather, the lockup with shuttle closed-open-closed really fast for one to four cycles between 40 and 65mph.  Above or below that, it won't shuttle.  

[pepsi71ocean]

23 hours ago, CSM said:

I am not an expert in the 12v.  
 

That said.  

 

I have been chasing my converter for a long time.  Mine comes, goes, and seems like my truck is a union truck. If I don't drive it much, it shifts perfectly.  If I drive it daily, about a month in, it starts to shuttle.  

 

I found improvements in cleaning or replacing grounds, replacing alternator that was way out of VAC spec. I also found improvment for a short time by cleaning my transmission output speed sensor.  

 

Beyond that, I haven't figured it out. It seems to be worse at high ambient temperature. Above 60F it gets more common to almost constant at 100F when I am driving at less than 65mph.  Above 65, I don't see any issues. 

I saw your post in anther thread but i figure ill ask it here.

Have you verified it is indeed alternator based when it is warm? If so do a vDrop test on your battery grounds, i suspect the drivers side is borderline failing, and sending the current to the passenger battery, and causing the noise.

 

This is exactly what happened to me with my 99. Except my issues came with heat and or humidity, if it was foggy out it was bad.

[CSM]

I put the alternator field on a switch.  I makes no difference if the alternator is powered or not. @pepsi71ocean No change.  This in itself is also odd, as the alternator field powers the trans relay, it shut the alternator down but didn't do jack to the trans. I haven't figured that part out. 

 

Interesting thought on batteries... I haven't done a voltage drop test.  

 

Thanks.  

[jlbayes]

I realize you have come down the path this is temperature based but have you checked out the brake switch?

[pepsi71ocean]

13 hours ago, CSM said:

I put the alternator field on a switch.  I makes no difference if the alternator is powered or not. @pepsi71ocean No change.  This in itself is also odd, as the alternator field powers the trans relay, it shut the alternator down but didn't do jack to the trans. I haven't figured that part out. 

 

Interesting thought on batteries... I haven't done a voltage drop test.  

 

Thanks.  

That is because the blue line runs from the PCM is the 12v+ that also powers the transmission relay. The alternator is charged by varying the ground (green) as resistance to the alternator field.

 

I discovered the issue by replacing my drivers side cable in an experiment, I told mike about it at one time when asking him about doing a vDrop test on the cables with my brother. While the ground cable did remove alot of the ac wave(on a drive test), I replaced both and still show reading on my fluke meter, however, thusfar the issue hasn't returned. (since replacing both cables)