Truck setting P0729 with tuner turned up

autotransmd

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Apr 8, 2021
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Hi everyone,

I've got a customer with a 2015 4x4 with duramax and allison. The truck has been deleted and tuned. I'm getting DTC P0729 when the tuner is turned up to 4 or 5, but not any other time. When the tuner is down or off, the transmission shifts perfectly. I've disassembled the transfer case and it is pristine inside. Barely any metal on the magnet and no excessive wear on any of the parts. There is no leak in the case and the fluid was full. Not sure if it matters, but it's an electronically shifted transfer case. I dropped the trans pan and it's the same story as the transfer case: it's pristine. The fluid is in perfect condition (truck only has 62,000 miles on it) and there isn't a speck of clutch material in the pan. I don't know the brand of tuner, but the work looks very professional and was done by a local shop that is highly regarded for this kind of work. Any suggestions on where to look next would be an enormous help to me!
 

Bdsankey

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That's a 6th gear incorrect ratio code. That typically means that one or both of the applied clutch packs for 6th gear (C2 and C4) have slipped. This means turn the power down, the OEM trans can only handle so much without added pressure via a TCM tune or an EPC fooler.
 

autotransmd

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Apr 8, 2021
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That's a 6th gear incorrect ratio code. That typically means that one or both of the applied clutch packs for 6th gear (C2 and C4) have slipped. This means turn the power down, the OEM trans can only handle so much without added pressure via a TCM tune or an EPC fooler.
If one of the applied elements was slipping under the additional torque from increased horsepower, wouldn't you expect to see the clutch burnt? I'm asking because there is zero clutch material in the pan and the guy has never had the pan off anywhere.

Additionally, what trans tune do you recommend for this?
 

Mike L.

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You will hardly ever see clutch material in the pan on a Allison. They will heat check the steels badly and glaze the frictions, but they will not shed material till they get destroyed. Now the converter clutch will shed and plug the heat exchanger.
 
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autotransmd

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Apr 8, 2021
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You will hardly ever see clutch material in the pan on a Allison. They will heat check the steels badly and glaze the frictions, but they will not shed material till they get destroyed. Now the converter clutch will shed and plug the heat exchanger.
I appreciate the information! I've almost got the trans out now to inspect it. Any advice on how to solve this so that I don't have this issue anymore?
 

Mike L.

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Build the trans and use my Ratio-tek pump and valve body kit. Make sure there is no trans tune or TCM fooler installed or you will break the trans in half. TCM must be stock.
 
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autotransmd

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Apr 8, 2021
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Build the trans and use my Ratio-tek pump and valve body kit. Make sure there is no trans tune or TCM fooler installed or you will break the trans in half. TCM must be stock.
I was told by the customer that there is no programming in the TCM. I'll verify that again. How/where can I purchase your kits? Also, is there any option for expedited shipping?
 

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