47RE Intermittent Limp Mode?

EDB

EDB

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Apr 2, 2014
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Wondering if anyone has ran into this problem before:

97 12V 4WD 47RE. Rebuilt 10k miles ago, Ultra Red clutches/frictions. Aftermarket valve body. Has shift kit installed. Triple disc DPC converter. billet input.

Start driving normally, and shifting with the column like I always do. Shifts great.

After driving 30-60 minutes and its warmed up, I will come to a stop sign and I will feel the transmission downshift on its own, even if I have the shifter in 2 or D.

I will accelerate from a stop, truck will wind out 1st gear and wont shift into second until very high in the RPM range. Even if I manually shift into 2.

When it finally shifts, it will be a very harsh shift.

Then when shifting from 2 into D, it will barely shift and feels like it just slides into gear. Then it will do this until I shut the key off and re-start. Then it will be fine.

Governor pressure sensor/solenoid has been replaced. Fresh transmission service. No difference.

Monitor trans codes/data stream everything seems fine. Output speed shaft sensor is working, Governor pressure increases with MPH and OSS signal.

Only thing I saw was Desired Gov Pressure was 126.8 psi and
Actual Gov Pressure was 71.0 psi

Any input guys? I've exhausted all options that I can think of

Only code I found was P1765 Transmission Volt Relay Circuit
 
Can you monitor the gov pressure signal to check and see if it exceeds 5v?

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Yes, the voltage KOEO was .45V, while driving, was around 3.48V
 
Is your throttle valve lever tied?

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Mine would limp after (I'm assuming) lockup and wasn't noticeable until I came to a stop. Key cycle required to fix. I wanted to use a zener diode to fix it, but ended up using a resistor. Yours doesn't sound entirely like that though.


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biggy238 said:
Mine would limp after (I'm assuming) lockup and wasn't noticeable until I came to a stop. Key cycle required to fix. I wanted to use a zener diode to fix it, but ended up using a resistor. Yours doesn't sound entirely like that though.


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Click to expand...

Yeah, mine doesn't seem to care if I lock it or not. It has done it without using the lock up switch and without. Its strange
 
Sounds to me like it possibly the resistor that is put in most transmission either up by computer but normally inside transmission next to valve body might have come lose from the wire. They put a resistor on one of the wires to fool the computer into thinking the line pressure is still normal etc. If it comes loss the computer think line pressure is not correct and throws it into limp mode.
 
I agree, the voltage seemed odd, and that could be a good reason why.

Could be a good time to jump to aftermarket controls if you determine it to be an electrical issue.

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Pulled the pan, checked valvebody wiring, all intact. Could not find a resistor of any kind in-line with any of the wires or any damaged/loose wires. Checked up at the PCM as well.
 
Pull the transmission relay in the fuse box and check your voltage with the key in the run position. Should be 12V at the relay with key on. If you have 12V there, check Pin 1 of the 8 pin connector and verify you have 12V supply at the transmission.

Lavon
 
Checked relay supply voltage, had battery voltage. Tested Pin 1, battery voltage again. Did a continuity test while wiggling harness, no breaks. Ohm reading seems normal
 
Another possibility:

Check the resistance of the overdrive and lockup solenoids, you can check them at the transmission plug if you rig up a mirror to give you a good view of the 8 pin connector at the tranny. Sometimes the small windings in the overdrive/lockup solenoids break and cause intermittent limp modes. Check between pin #1 and pin #6 for overdrive and pin #1 and #7 for lockup. These resistance values should be around 40 ohms and they should be nearly identical, if they are not, I suggest pulling the VB and replacing the od/lockup solenoids and the harness assembly about $75 to $100 when purchased as a complete assembly.

You can also check resistance at the PCM connector if you want to troubleshoot the truck harness and trans harness/solenoids as an assembly.
 
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