"Thumping" with auto shifting?
03-05-2007, 01:20 AM
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"Thumping" with auto shifting?
When Im using the triptronic I get sometimes get a transmission shift thump when I shift to third. I shift without dropping off the gas as intended...anyone else have this issue?
04-18-2007, 12:31 AM
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You know its a good thing I was searching. I was actually searching for a different reason, but my 06 does this same thing. Pretty much everytime I go into third. I'm glad to hear I'm not the only one. Does anyone know what causes this?
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04-19-2007, 05:45 PM
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I hope Aggro_Al doesn't mind me pasting some info from one of this old posts.
"The Nissan 5AT is a torque converter based performance tranny. The tranny is a real -time learning and adaptable transmission. The jolt you feel is mainly caused by two things and to a small degree the locked/coupled gear ratio difference between 2nd and 3rd gear.
The first thing that causes the jolt is the speed at which the 5AT shifts. If it detects that you are performance driving it will adapt it's shift speed to it's fastest setting and to the learned drivers style. This shift can happen faster than a blink of an eye. The Porsches do it in <200ms (yes, those are milliseconds) and the Nissan 5AT is very similar to that transmission which leads me to believe they will be in the same neighborhood. A human eyeblink is ~300ms for reference and a pro NASCAR driver can manually shift in ~0.7-0.8s.
The biggest reason for the jolt while in WOT is torque multiplication. You will get an instaneous boost in torque at the shift. The shift happens so fast that the tranny will have the ability to use more of it's torque multiplying ability. Torque multiplication is when the tranny outputs more torque to the driveshaft than the engine torque that is being input into the tranny. Many people think in error that a torque converter loses power. A torque converter actually has the ability to create more power to the driveshaft than what the engine alone is outputting. When the impeller (engine side) is spinning faster than the turbine (driveshaft side), like when you are at WOT and shifting, the stator will return excess fluid back to the impeller where the engine has an oppourtunity to re-accelerate the unused fluid to create more torque. The stock Z can almost double the engine torque some pro drag vehicles have 4x & 5x torque mulipliers. As, the fans get closer together in speed the stator gradually reduces the energy return to allow the fans to couple or lock.
The next thing that can cause a jolt is the the difference that the coupled 2nd gear ratio to the locked 3rd gear ratio makes. It's a pretty good size jump. But, because the 5AT uses a torque converter it has the ability to variably gear down to make that difference less then gradually return to the locked gear ratio.
On the 5AT, 1st, 2nd & 3rd have the ability to torque multiply. 4th gear and 5th gear are full lock-up gears. 4th and 5th gears use a mechanical clutch and don't use fluid coupling or fluid torque flow. You don't feel the jolt as much in 4th and 5th because they act just like the gears in a regular MT. They will not use fluid torque multiplication."
"The Nissan 5AT is a torque converter based performance tranny. The tranny is a real -time learning and adaptable transmission. The jolt you feel is mainly caused by two things and to a small degree the locked/coupled gear ratio difference between 2nd and 3rd gear.
The first thing that causes the jolt is the speed at which the 5AT shifts. If it detects that you are performance driving it will adapt it's shift speed to it's fastest setting and to the learned drivers style. This shift can happen faster than a blink of an eye. The Porsches do it in <200ms (yes, those are milliseconds) and the Nissan 5AT is very similar to that transmission which leads me to believe they will be in the same neighborhood. A human eyeblink is ~300ms for reference and a pro NASCAR driver can manually shift in ~0.7-0.8s.
The biggest reason for the jolt while in WOT is torque multiplication. You will get an instaneous boost in torque at the shift. The shift happens so fast that the tranny will have the ability to use more of it's torque multiplying ability. Torque multiplication is when the tranny outputs more torque to the driveshaft than the engine torque that is being input into the tranny. Many people think in error that a torque converter loses power. A torque converter actually has the ability to create more power to the driveshaft than what the engine alone is outputting. When the impeller (engine side) is spinning faster than the turbine (driveshaft side), like when you are at WOT and shifting, the stator will return excess fluid back to the impeller where the engine has an oppourtunity to re-accelerate the unused fluid to create more torque. The stock Z can almost double the engine torque some pro drag vehicles have 4x & 5x torque mulipliers. As, the fans get closer together in speed the stator gradually reduces the energy return to allow the fans to couple or lock.
The next thing that can cause a jolt is the the difference that the coupled 2nd gear ratio to the locked 3rd gear ratio makes. It's a pretty good size jump. But, because the 5AT uses a torque converter it has the ability to variably gear down to make that difference less then gradually return to the locked gear ratio.
On the 5AT, 1st, 2nd & 3rd have the ability to torque multiply. 4th gear and 5th gear are full lock-up gears. 4th and 5th gears use a mechanical clutch and don't use fluid coupling or fluid torque flow. You don't feel the jolt as much in 4th and 5th because they act just like the gears in a regular MT. They will not use fluid torque multiplication."
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