Allison trans tuning questions

Hello, I'm posting this in the Diesel Engine category, being it seems most of the transmissions in the tranny section are gas. I had a couple of questions on the Allison trans tuning. I've tuning 4l60e,4l80e, 6l80e transmissions before. But this Allison seems like I can not get it to shift smooth. It always seems too firm. The trans supposedly has modified valve body, and a billet converter. I reduced line pressure in 10% increments, but it still slams into gear. On a rare instance it will shift pretty good and firm. But it seems it is not repeatable. Drove it around and tried to let adaptives learn, but seemed to just get worse. Also downshifts are crazy, slipppp and bang. It is odd that none of the shifts work very well. Is it possible that modified valve body could have something to do with it,and the billet converter? Vehicle is 8.1 gas truck with Allison 5 speed. Any input would be appreciated!

Tough question. Not knowing what "shift kit/mod" is in it you will have a heck of a time. If the adapts can't adjust to a reasonable level you won't be able to change it with software. Hate it when it goes to a trans shop and they physically alter for harsh shift. Makes tuning for the perfect shift next to impossible other than if it was just a simple light line pressure increase.

is there a recommended Allison line pressure increase? Had it been increased/tuned before or just the physical mods? It seems odd that you are reducing line pressures that much without successful change.

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Originally Posted by TheMechanic

Tough question. Not knowing what "shift kit/mod" is in it you will have a heck of a time. If the adapts can't adjust to a reasonable level you won't be able to change it with software. Hate it when it goes to a trans shop and they physically alter for harsh shift. Makes tuning for the perfect shift next to impossible other than if it was just a simple light line pressure increase.

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Yeah, I'm kinda feeling the modified valve body is causing it issues. I will get a hold of the trans guy and ask what his valvebody mod consists of..

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Originally Posted by Stroked06Goat

is there a recommended Allison line pressure increase? Had it been increased/tuned before or just the physical mods? It seems odd that you are reducing line pressures that much without successful change.

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No, I started with a stock tune file. It was stock before, then the owner put a big single on it. While he was doing the turbo install, he had the trans rebuilt. I've came down well below stock shift pressures and it still is way harsh.

When doing a 2 Bar Sd conversion, does it affect the trans side? Is is proper to Write Entire including the Tcm, when doing 2 bar Sd conversion?