Help with lightly modified L31-R

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davkenrem

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Trans issue after 0411 PCM Swap
I have a 1997 Chevy K1500 Suburban, with a new L31-R Crate engine and rebuilt 4l60e. I did a 0411 PCM Swap to add efans and tune for the cam and headers. I used a 0411 PCM from a 2002 GMC Savana 2500 with the 5.7l and a 4l80. I did a segment swap from a Chevy Express 1500 with the 5.7l and a 4L60. I brought over the trans and trans diag from the 4L60. Used HP Tuners.

After the initial swap the trans shifted well other than the shift point came at a lower rpm than expected. I have not messed with those yet.

Been driving it for 3 weeks that way with no issues.

Saturday I made a 25 mile round trip to a friends house. About half way there the truck began to no longer shift back to first gear after coming to a stop. Seemed like it was still in OD. I would have to manually down shift into first and then take off then shift to third or OD and it would upshift fine. But at the next stop light same thing again. Got to my destination and checked trans fluid and it was full.

I let the truck set for about two hours then went to go home same thing again, about half way there no down shift at a stop.

I am very new to PCM Programming so I'm not sure if this is a PCM issue or a transmission Issue. I'm leaning toward PCM since the issue is intermittent.

Anyone have any ideas? Thanks in advance.

Can email tune if anyone wants to look at it.
 

Christian Steffen

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Trans issue after 0411 PCM Swap
I have a 1997 Chevy K1500 Suburban, with a new L31-R Crate engine and rebuilt 4l60e. I did a 0411 PCM Swap to add efans and tune for the cam and headers. I used a 0411 PCM from a 2002 GMC Savana 2500 with the 5.7l and a 4l80. I did a segment swap from a Chevy Express 1500 with the 5.7l and a 4L60. I brought over the trans and trans diag from the 4L60. Used HP Tuners.

After the initial swap the trans shifted well other than the shift point came at a lower rpm than expected. I have not messed with those yet.

Been driving it for 3 weeks that way with no issues.

Saturday I made a 25 mile round trip to a friends house. About half way there the truck began to no longer shift back to first gear after coming to a stop. Seemed like it was still in OD. I would have to manually down shift into first and then take off then shift to third or OD and it would upshift fine. But at the next stop light same thing again. Got to my destination and checked trans fluid and it was full.

I let the truck set for about two hours then went to go home same thing again, about half way there no down shift at a stop.

I am very new to PCM Programming so I'm not sure if this is a PCM issue or a transmission Issue. I'm leaning toward PCM since the issue is intermittent.

Anyone have any ideas? Thanks in advance.

Can email tune if anyone wants to look at it.


It doesn't sound like a tune issue.. but email it to [email protected] and I'll check it over when I get a chance.
 

L31MaxExpress

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Doesn't sound like a tune issue to me either. I would check the 1-2 shift solenoid pin into the PCM. I have also seen many GM shift solenoids die unexpectedly. The 3-4 solenoid in my Tahoe started going out and would randomly cause the transmission to drop out of overdrive on the highway.
 

davkenrem

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I was finally able to duplicate the issue. most of my drives this week were back and forth to work, which is about 7-10 minutes. this morning driving to church took about 30 minutes and I experienced the issue again. Just finished looking at the log file and trans fluid temp got to 249 degrees.
Something is seriously wrong.
I'm pretty sure I drove the truck back and forth to church and further before the PCM Swap.

Trans temp went past 176 degrees after 12:33 mins of driving on surface streets. At 14:22 mins in I experienced the first no downshift and Temp was 190 degrees. Temp reached a max of 239 degrees 23:34 mins into trip.

Is there anything tune related that could cause this?
 

Schurkey

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Method 1.

Drive 50+ mph at steady speed. TOUCH the brake pedal with your left foot while holding the gas pedal steady with your right. Does the engine RPM increase? Torque converter unlocked with brake application as it's supposed to.

No RPM increase? Torque converter probably wasn't locked to begin with.

Method 2.

Count the upshifts as the vehicle accelerates slowly to highway speed. You should feel 1--2, 2--3, 3--4 upshifts, plus one more bump as the converter clutch engages. Feels like four "shifts" but the converter clutch can be very gentle. Might have to watch the tach to see the four drops in RPM.

Method 3.

Connect a scan tool, look for the converter clutch engagement notice on the tool.
 

davkenrem

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Method 1.

Drive 50+ mph at steady speed. TOUCH the brake pedal with your left foot while holding the gas pedal steady with your right. Does the engine RPM increase? Torque converter unlocked with brake application as it's supposed to.

No RPM increase? Torque converter probably wasn't locked to begin with.

Method 2.

Count the upshifts as the vehicle accelerates slowly to highway speed. You should feel 1--2, 2--3, 3--4 upshifts, plus one more bump as the converter clutch engages. Feels like four "shifts" but the converter clutch can be very gentle. Might have to watch the tach to see the four drops in RPM.

Method 3.

Connect a scan tool, look for the converter clutch engagement notice on the tool.




Thanks
 

L31MaxExpress

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Method 1.

Drive 50+ mph at steady speed. TOUCH the brake pedal with your left foot while holding the gas pedal steady with your right. Does the engine RPM increase? Torque converter unlocked with brake application as it's supposed to.

No RPM increase? Torque converter probably wasn't locked to begin with.

Method 2.

Count the upshifts as the vehicle accelerates slowly to highway speed. You should feel 1--2, 2--3, 3--4 upshifts, plus one more bump as the converter clutch engages. Feels like four "shifts" but the converter clutch can be very gentle. Might have to watch the tach to see the four drops in RPM.

Method 3.

Connect a scan tool, look for the converter clutch engagement notice on the tool.

Except the 0411 Express van tune locks 2-4 even during acceleration and even at WOT.
 
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