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47RE no lockup when cold

Old 01-11-2019, 08:40 PM
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47RE no lockup when cold

Looking for suggestions on what to check next. Here is the situation:

1997 4x4 2500 with 47RE trans

I installed a Suncoast valve body in August, with all new electronics.
Every thing was fine until temps started getting cold (upstate NY). Now it wont lockup 4th gear until I drive 8 miles, and the engine is fully up to temp.
I put in a 190 degree thermostat and have the radiator and trans cooler blocked off. It made no difference. Engine warms up like normal, good heat in cab, temp gauge reads correctly.
Factory service manual says the thermistor (temp sensor) is in the Governor Pressure Solenoid. So I dropped the pan and replaced that, even though it was only a few months old. Made No difference.
I know it is temp related because it always starts to work at the exact same place in my morning commute, and it will continue working fine as long as it is warm.
This did not happen with the original valve body.
Suncoast told me there are two temp senors, where is the other one? (I thought the cylinder head coolant sensor is just for the gauge, is this correct?) My gauge reads correct.
Any suggestions on what else to check?
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Old 01-15-2019, 04:20 PM
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This is a downloadable factory manual for a '96 - sorry, I don't have a link for a '97, but you can find the '97 manual at Geno's Garage. As far as I know, '96s and '97s are pretty much the same (disclaimer of your choice here...). I'd look through that manual and see what you can find on transmission temperature sensors - I'm only aware of one on my '96. If Suncoast says there are two, I'd ask them where the other is. If there is a relationship with an engine coolant temp sensor, it "should" be spelled out in the FSM. You might also see if you can find an ATSG manual for the 47RE and see what it says. Monitoring trans temp with a scan tool could be a good idea, but it's a toss-up as to whether the scanner can correctly read that - I have a SnapOn Modis that says my 47RE trans temp is 14,000+ degrees (always) but my ancient OTC Enhanced Monitor reads it just fine... If you read up in the FSM on how the sensor works, perhaps you could monitor it with a multimeter, long test leads, and backprobes. That won't tell you what temp the PCM thinks it is, but could give you insight as to whether there is a fairly steady change in signal. Also, consider checking continuity/resistance between internal trans connector, external connector, and PCM - maybe something's interfering with the connections and it doesn't go away until a certain temperature is reached
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Old Yesterday, 08:15 PM
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Thanks for the suggestions.
I already have the FSM for 1997.
Its says the " PCM prevents engagement of the converter clutch and overdrive clutch when fluid temp is below 50 degrees (F)."
It also says:
The conditions under which a shift to fourth will not occur are:
Overdrive switch off
Trans. fluid temp. below 50 or above 121 F
Shift to third not completed
Vehicle speed too low for 3-4 shift
Battery Temp. below -5 degrees F

So I suppose it is possible that the battery temp sensor is faulty. I will test that.
Suncoast couldn't offer any help other than telling me I need to put it on a scanner.
I dont have a scanner and always do all my own work on my vehicles...what scanner do I need and is it affordable for a DIY situation?
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