48re won't downshift at a stop.

QMFB

QMFB

Fastest Welder in Texas
Ok gentlemen, I've got a trans issue here.
Brand new ATS Stage 6 (I know, I know) behind a fresh built 6.4
Less than 200 miles on it, and now it will not downshift at a stop in drive. If I come to a stop and manually shift to first it will engage and I shift right back to drive.

So I broke out the ATSG manual, and it suggests gov solinoid and transducer are faulty.
Hooked a manual pressure guage up to the governor port.
ATSG says if pressure is 0 in drive, then a servo is stuck.
And if pressure is 7-12psi then the gov solinoid or transducer is at fault....

Ok easy enough, right ?

So I hook up the pressure guage, start the truck and put it into Drive.

Pressure is "average" at 120psi. And I say average because the needle is bouncing wildly between 105 and 135.

Any guidance would be appreciated.
 
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This was instantly when I put it in drive
 

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How is the throttle valve configured on this one?

I *think* this is probably a flooding governor pressure solenoid, but would like trans known trans guys to weigh in.

Sent from my XT1575 using Tapatalk
 
Well I feel like a tard... Just realized I had my pressure guage hooked to the accumulator port yesterday, not the governor port. Doh !

I'm gonna go out shortly and test again in the correct port.
 
Hooked the mechanical guage up to the correct port, started the truck and placed it in Drive with brakes applied...

Pressure reading is 0.

WTH ?
 

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I'm hoping not. Went way over budget building this truck, and even though this trans is brand new, my warranty is over. So, I'm hoping something cheap will be the fix for now, lol.
Checked pin #2 at the case connector with the key on. Got 4.99 volts... So that's good at least.
 

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Did you adjust your throttle valve?
I'm almost certain that's the issue now that you have the gauge sorted.

Sent from my XT1575 using Tapatalk
 
Throttle valve is set with about 1/8" of slack @ 0% throttle... So it can't get any lower ?

Probed pin #4 (governor pressure sensor signal) at the case connector, plugged in, key on.

Got .446 volts.

That's about .2 volts low according to the ATSG... Issue ?
 

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Probed pin #5 at the case connector, plugged in, engine RUNNING in Drive.

Got 1.2 volts and change. Some fluctuating.

ATSG is showing it should be about 8.3 volts ???
 

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This final paragraph says 8.3 volts OR LESS. But it also says 12psi (I would assume ANY psi) but my mechanical guage reads 0 psi.

And there is no "path" in this manual for that situation ?
 

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Could really use some help here. I built my own 6.4 engine, and enjoyed every minute of it... But I AM NOT a transmission guy ! Lol ��
 
This showed up. P0713, Trans temp sensor voltage too high.

Don't know if this helps diagnostic.
 

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This is with key ON and engine NOT running.
 

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Does it take off in first the first time you drive it for the day? gov. pressure should almost match road speed. If you can take it for a cruise monitor the pressure and see if it falls to zero at a stop. Not sure if ats still uses a VBA valvebody assist to cheat the voltage to the governor pressure solenoid, dtt also had a little box with a small screw to change voltage, this is what I run on my 03. Let us know im sure barney will get straightened out,,,,
 
Yes, it will take off in first gear when the truck is first started. After that it needs to be manually shifted into first at every stop, or it will take off in second (or third?).
 
Im not a fan of "throwing parts" at a problem, but it seems my only solution right now is to just replace the transducer and the Gov solinoid.
Hate to do that, because the diagnostics I ran were "inconclusive" to say the least.
 
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