tording99Z28

iTrader: (3)

I am just curious if anyone else has seen this issue with a built transmission. If I am cruising at say 50 mph and the car is in OD and I go WOT the transmission downshifts fast and hard to 2nd and the car takes off like a bat out of hell. Same scenario, if I am cruising at 50 mph and the car is in D instead of OD and I go WOT the car takes off in 3rd for a second and then downshifts into 2nd and takes off like a bat out of hell. So my question is why is there a delay on the 3-2 downshift when in D but when in OD there is no delay at all? Anybody else seen this issue?

The transmission has performed flawlessly and shifts hard and fast all the time on upshifts, this is the only issue I have seen with it and I am just more curious I guess as to why this is. Thanks

performabuilt

iTrader: (25)

I am not sure of the reasoning for this occurance but I have noted it in some cars over the years with both built and stock trans. I have always assumed there was some difference in the strategy in tuning for the 2-3 in the D position as opposed to the OD position. The only way to know for sure I think however would be to physically monitor what the solenoids are being told to do each way. I do know the 2-3 takes slightly longer to complete in the D position over the OD position due to the overun clutch coming on during the 2-3 shift in D where its not used during the 2-3 in OD.

01ssreda4

iTrader: (96)

mine does something similar (its a factory trans) at 75 mph in OD, WOT it jumps to third while unlocking and you blast off. in D at 75 you go WOT and it shifts to third, then you go in third for about second at a fairly low rpm (bc the converters is still locked) then after a second the converter unlocks and you blast off. dunno why the converter is sluggish releasing in D......it does this in 2nd too IIRC

cals400ex

iTrader: (27)

does that mean it is more beneficial to leave the car in OD instead of D when racing?

tording99Z28

iTrader: (3)

Thats what he has recommended for me and thats what I have done thus far. It only happens when going from a roll so this is the only time you would need to be in OD. When racing at the track from a standing start I think I can be in D and there should be no difference between D and OD.

tording99Z28

iTrader: (3)

As far as your comment Frank, I have HPtuners and from what I see there is no way to change the shifting strategy between D and OD in the tune. The tables dont differentiate between D and OD. I will setup a trans file and log what the solenoids are doing when going WOT from a roll and hopefully this will tell us whats going on.

performabuilt

iTrader: (25)

IDK really thats just been my assumption, I noticed it in a few camaros i have driven but do not know what the reason is myself. Just guessing

performabuilt

iTrader: (25)

As far as the 2-3 shift yes since there would be a little more volume of fluid available to the clutch set with the overun not coming on at the same time during the shift.