malatu
Member
Folks, here is a cut n paste from another form another forum (not sure your allowed to provide links to other forums, but would be glad to provide it). It's the first technical explanation that attempts to explain the shift delay between 1st and 2nd gear during cold weather. At the bottom of the post, there is a link that provides additional explanation. I don't know if any of the info is technically accurate but I'd like to think it is. Usually if someone posts inaccurate info, other's quickly provide corrections.
Up to this point in time, all I've ever read is is: "Don't worry about it, this shift delay is normal!" Ugh!
Below is the cut n paste from another Ram Forum:
*************************************************************************
My understanding of how the 8HP70 shifts is:
There are 5 clutches in the transmission, 3 of which are always "engaged" depending on the gear (except neutral and presumably which have none engaged)
Actual shifting pattern is setup so that 2 of the clutches from the previous gear remain engaged while the 3rd one changes to a "different" clutch. Im thinking thats how they can claim such quick shift times, its really only letting go of one clutch and then gripping another. 1st gear has clutches A,B,C engaged, 2nd gear has A,B,E, so the shift involves changing from C to E but leaving A and B.
As such, I would think that any "slip" during a shift is actually a delay between the "moving" clutch letting go and the "new" clutch engaging. What could cause the delay? I would think thicker (i.e. cold) fluid could cause that for sure. Low fluid levels could lead to low pressure levels which could cause it too. Or it could be the software "waiting" to call for the next clutch to engage...that could be a programming issue or maybe even a learned (adaptive) behavior issue.
Honestly don't think its a physical issue with the transmission....I kinda think it gets learned just by how you or I drive and then it gets "stuck" with the bad behavior. Oddly enough, mine started slipping its 1-2 shift for the first time yesterday with 1500 miles on the truck. I was also starting off in 4-Auto which I usually dont do, not sure if that makes a difference.
After changing back to 2WD and starting off slowly (instead of a rush like I was doing when it first happened), the shift acted like it normally does....its not FAST, it seems to draw itself out a bit, but there was no RPM rise during the shift. Also note it never did it again from a dead stop...granted the fluid was warmer at that point, but it only seemed to happen on the first or second 1-2 shift.
EDIT: also, at one point I think there was a TCM update to alleviate a harsh 1-2 shift....I wonder if that causes the transmission to delay the 1-2 shift on purpose. Found a good post from transengineer on this forum about how the transmission actually does the shift:
__________________
If you cant Dodge 'em, RAM 'em.
Up to this point in time, all I've ever read is is: "Don't worry about it, this shift delay is normal!" Ugh!
Below is the cut n paste from another Ram Forum:
*************************************************************************
My understanding of how the 8HP70 shifts is:
There are 5 clutches in the transmission, 3 of which are always "engaged" depending on the gear (except neutral and presumably which have none engaged)
Actual shifting pattern is setup so that 2 of the clutches from the previous gear remain engaged while the 3rd one changes to a "different" clutch. Im thinking thats how they can claim such quick shift times, its really only letting go of one clutch and then gripping another. 1st gear has clutches A,B,C engaged, 2nd gear has A,B,E, so the shift involves changing from C to E but leaving A and B.
As such, I would think that any "slip" during a shift is actually a delay between the "moving" clutch letting go and the "new" clutch engaging. What could cause the delay? I would think thicker (i.e. cold) fluid could cause that for sure. Low fluid levels could lead to low pressure levels which could cause it too. Or it could be the software "waiting" to call for the next clutch to engage...that could be a programming issue or maybe even a learned (adaptive) behavior issue.
Honestly don't think its a physical issue with the transmission....I kinda think it gets learned just by how you or I drive and then it gets "stuck" with the bad behavior. Oddly enough, mine started slipping its 1-2 shift for the first time yesterday with 1500 miles on the truck. I was also starting off in 4-Auto which I usually dont do, not sure if that makes a difference.
After changing back to 2WD and starting off slowly (instead of a rush like I was doing when it first happened), the shift acted like it normally does....its not FAST, it seems to draw itself out a bit, but there was no RPM rise during the shift. Also note it never did it again from a dead stop...granted the fluid was warmer at that point, but it only seemed to happen on the first or second 1-2 shift.
EDIT: also, at one point I think there was a TCM update to alleviate a harsh 1-2 shift....I wonder if that causes the transmission to delay the 1-2 shift on purpose. Found a good post from transengineer on this forum about how the transmission actually does the shift:
__________________
If you cant Dodge 'em, RAM 'em.
