Duramax Diesels Forum Truck of the Week
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Old 10-03-2018, 05:46 AM
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Default Harsh 2-1 Downshift

Its not all the time, and I can't seem to recreate it consistently.

But coming to a stop, if I stop quickly, seems to hang in 2nd, then when stopped clunk into 1st. A harsh clunk at that. BUT, if I slowly stop, I can watch on the CTS it go 2-1 with no issue.

Thoughts?
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2005 LLY: AFE Bladerunner, MBRP downpipe, sewer pipe exhaust, PPE tuner, !EGR

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Old 10-03-2018, 07:31 AM
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Try a different tune.
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Old 10-03-2018, 07:35 AM
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Quote:
Originally Posted by Mike L. View Post
Try a different tune.
Will do, also was going to do a trans relearn.

Come Monday I am swapping fluid and spin on filter since they are due as well.
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2005 LLY: AFE Bladerunner, MBRP downpipe, sewer pipe exhaust, PPE tuner, !EGR

1995 Z28: 76mm, 383ci LTwon, 80e 660hp/750ft-lb 10.2@140

2014 CTD Stock
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Old 10-03-2018, 07:57 AM
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Quote:
Originally Posted by lts1ow View Post
Will do, also was going to do a trans relearn.

Come Monday I am swapping fluid and spin on filter since they are due as well.
Don't do that.
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Old 10-03-2018, 08:05 AM
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Quote:
Originally Posted by Mike L. View Post
Don't do that.
Fluid swap, or trans relearn?
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2005 LLY: AFE Bladerunner, MBRP downpipe, sewer pipe exhaust, PPE tuner, !EGR

1995 Z28: 76mm, 383ci LTwon, 80e 660hp/750ft-lb 10.2@140

2014 CTD Stock
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Old 10-03-2018, 08:06 AM
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Quote:
Originally Posted by lts1ow View Post
Fluid swap, or trans relearn?
trans relearn.
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Old 10-03-2018, 11:16 AM
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What tcm os are you running? 01 or 05? Some of the 01 os's have a harsh 2-1 downshift(there's a tsb about it).
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Old 10-03-2018, 04:02 PM
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Quote:
Originally Posted by THEFERMANATOR View Post
What tcm os are you running? 01 or 05? Some of the 01 os's have a harsh 2-1 downshift(there's a tsb about it).
Its a canned PPE tune, and it is a sudden issue. Truck has been tuned like this for a few years now.
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2005 LLY: AFE Bladerunner, MBRP downpipe, sewer pipe exhaust, PPE tuner, !EGR

1995 Z28: 76mm, 383ci LTwon, 80e 660hp/750ft-lb 10.2@140

2014 CTD Stock
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Old 10-03-2018, 04:06 PM
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My old LB7 started doing strange things when cold on the 2-1. Couldn't ever figure it out, and it wasn't the driveshaft, I already lubed it.

Flash forward 6+ months and after servicing the brake system, gone. I replaced all four corners with new pads, rotors, and flushed the fluid. I could be a coincidence, but I would bet not.
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