Suvlaki

Forgive me if this has already been discussed, I was unable to find it using the search.

My '06 A/T kicks into 3rd gear. I have never thought much of it since that is the way it has come from the factory, but I am curious to see if this is normal. It is more noticeable in the manumatic mode, when shifting from 2nd to 3rd at > 4000 rpms. All of the other gears shift seamlessly but the 3rd seems to kick and make a "thump" noise.

Jus' curious to see if this is normal for A/Ts or if I should actually *gulp* ask the dealer.

Demon Z

iTrader: (1)

Yeah, mine does that too. ('05 Touring) It varies by rpm and throttle position. I don't worry about it, but it's just the 2-3 shift that does it.

ings350z

mine does it too. I was going to take it in but now it seems to be the norm

oren

yeah mine does it too, i kinda like it though.

sq40

iTrader: (4)

My 04.5 ZR 5AT does not pop or make any sort of noise when shifting to 3rd??

jenna350z

Same problem here. But I thought it was cause of my reflash.

bmac03z

Sorry to highjack the thread but ....... If I'm riding in 3rd and at higher Rpm's in sportshift mode my AT decides it wants to be in 4th on its own. Anyone else?

Cannysage

iTrader: (29)

it's not normal but mine does it too...

bmac, it should never upshift like that.

bmac03z

It's pretty dangerous when you let off the gas going into a corner expecting to slow down and it upshifts and speeds up

3hree5ive0ero

iTrader: (95)

Should've gotten the 6MT.

We can decide whether the gear "kicks" or not

bmac03z

Yeah I would have but my wife can't drive a 6MT so this was the only way I could buy it.

ChuckGZ

mine didn't kick from 2 to 3 noticeably until i got the SGP VB upgrade, but that kinda brought it out. it's not bad, and like you said it varies with RPM's / load. my car's in the shop now getting a high stall torque converter. Hopefully that eases up the bump a little.

Suvlaki

What is "higher rpms"? It shouldn't upshift by itself but I have read that if you are redlining it (or close to relining) for a while, it will automatically shift up to prevent wear on the engine...

bmac03z

3-5.5Krpms, I'm not bumping the rev limiter or anything.

Suvlaki

mmm... mine doens't do that... how long are you riding until it upshifts?

cruddydude

My stock '05 does it too. Sometimes, I get a very harsh physical jolt during upshifts. It only happens in manual mode, and only on the 2-3 upshift. The dealer told me it's "normal." I'm not convinced. While I can live with the nuisance of an occasional loud bang, I'm more concerned that it might cause damage over time.

bmac03z

It doesn't do it every time. I pretty much take the entire road in third gear which is a farely curvy 6 miles or so

imjdoggie

iTrader: (2)

my 2-3 is a little quirky too, I really don't use the manual mode I feel like I'm abusing the tranny. I had to replace the tranny in my 01 Maxima MT 2500 beans. THAT F-IN Stank!!!

Nismo 350z

Not true. I reflashed and I can take it to 7100rpm and it wont shift up or down in manual mode. I have to shift it. BTW it also happens to me in the 2-3 shift but only when I am at WOT. I think the LSD locks up for a while.

Aggro_Al

Your tranny should not shift up on it's own in while in manual-mode until you shift it. The tranny will not let you stall either, the tranny will downshift automatically if you drop below the stall speed and don't shift yourself.

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.

http://www.protorque.com/techi/ti_faq.htm#3