I know the Allison has to shift sequentially so it can't go from say 5th to 3rd, but I don't get why it takes so long for it to downshift say when your coasting in 5th and go WOT. I feel like there would be virtually no turbo lag if the trans could downshift faster and help build boost faster with more rpms?
Why does the allison take so long to downshift?
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I buy items from them often. He mentioned about riding in a dmax that was EFI live tuned. I asked him who it was so I was just guessing it may be you. I custom tune my own and work on trucks ocasionally.
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depends on vehicle speed at the time you went from part throttle to WOT
if you actually are in 5th gear at say 50mph it could actualy go from 5th to 3rd without damage.. especially if the TCC is locked.
tunning has alot to do with it..
if you actually are in 5th gear at say 50mph it could actualy go from 5th to 3rd without damage.. especially if the TCC is locked.
tunning has alot to do with it..
OK I will have to look for your truck around. I thought the way the valve body is it was impossible for the Allison to skip gears while shifting.
I have heard this too. All my logs show it transitioning through 4th, just briefly. I don't think it ever "finishes" shifting to 4th before starting the shift to 3rd, so it is kind of like a slow skip shift.
Anyone see a log where it skips a gear entirely?
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This is correct. The valve body must go through every gear to do a downshift from say 6th to 3rd. Teh valve body doesn't just use one solonoid for each clutch pack, but uses 2 trim solelonoids to control all line pressure to the clutch packs and a series of 3 shift valves to control where the trim solenoids and line pressure goes. For the 5th to 3rd downshift, it has to go from holding the C2's to line pressure and transfer line to the C1's and then hand off the trim fluid from the C3's back to the C3's during the line pressure hand off. So the trans must go through the gears sequentually EVERY time to avoid a tie up which results in hard parts shattered.