06 3500 A/T Shift Issue
09-08-2011 | 01:10 PM
#1
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From: Texas
06 3500 A/T Shift Issue
I recently had the transmission rebuilt in my dually (it only lasted 264,000 miles pulling a 30' 10k trailer 
). Since I got it back it seems to have developed a shifting issue, while pulling a hill the computer downshifts the tranny to second running the RPM's up to about 3400, not good. The dealer said it’s a transmission problem, the tranny shop said it’s a computer issue.......
The transmission shop said something about high ECM voltage and some kind of throttle valve actuator issue? They don't deny that the computer is telling the tranny to down shift, they just don't understand why it's downshifting so far ie. from OD to first @ 45 MPH when you put your foot in it.
). Since I got it back it seems to have developed a shifting issue, while pulling a hill the computer downshifts the tranny to second running the RPM's up to about 3400, not good. The dealer said it’s a transmission problem, the tranny shop said it’s a computer issue.......The transmission shop said something about high ECM voltage and some kind of throttle valve actuator issue? They don't deny that the computer is telling the tranny to down shift, they just don't understand why it's downshifting so far ie. from OD to first @ 45 MPH when you put your foot in it.
09-09-2011 | 10:50 AM
#3
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From: McDonough GA
The shifting around 1st, 2nd and drive is all hydraulic and not controlled by the computer. If it is actually down shifting all the way to 1st at 45 mph that is a transmission build result not the computer.
The ECU controls 2 things on your transmission, governor pressure and throttle valve pressure. These influence shifting, not control it so the actual hydraulic setup has to be correct or you will have issues.
Is it possible to have the trans downshift from drive to 1st at 45 mph? Yes and that is controlled by how the VB is setup, TV pressure vs governor pressure.
Make sure that both the gov pressure transducer, gov solenoid and speed sensor was replaced with the rebuild. The transducer and solenoid can be bad out of the box.
The TTVA motor that controls the TV pressure is a known problem area. If there are codes indicatiing the voltage is to high too long on the motor it could be jamming open or sticking where it should be moving freely.
The ECU controls 2 things on your transmission, governor pressure and throttle valve pressure. These influence shifting, not control it so the actual hydraulic setup has to be correct or you will have issues.
Is it possible to have the trans downshift from drive to 1st at 45 mph? Yes and that is controlled by how the VB is setup, TV pressure vs governor pressure.
Make sure that both the gov pressure transducer, gov solenoid and speed sensor was replaced with the rebuild. The transducer and solenoid can be bad out of the box.
The TTVA motor that controls the TV pressure is a known problem area. If there are codes indicatiing the voltage is to high too long on the motor it could be jamming open or sticking where it should be moving freely.
09-09-2011 | 11:06 AM
#4
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From: Texas
Thanks, I'll look into whether or not the shop replaced those components when they did the rebuild. I had a problem about 100K back where the transmission wouldn't up shift and the same shop replaced the gov solenoid fixing that problem. The rebuild issue was because the torque converter and pump cratered and ripped all the flywheel mounting lugs off the torque converter.
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