my theory on why Z/G trannies have so many problems...
10-08-2005, 01:19 PM
#21
Originally Posted by 2JZfan
it's true that we don't have a percentage for how many tranny failures there have been. On the other hand, if you look around at forums for Camaros, Vettes, Vipers, Cobras, etc. I don't see the 400+ post threads about "yeah I had to have my tranny replaced too"...
As far as the tranny being able to do its job "no matter what the engine is doing" that's true to a point... it is the synchro's job to match the speeds, but obviously the greater the speed differential, the more work it has to do and the faster it will wear out... when you shift quickly, you are doing several things at once - letting off the gas, pushing in the clutch and pulling the shifter into the next gear... there will be a period there where you have only partially disengaged the clutch and yet you've already pulled out of the previous gear... at this point, more engine rpm amounts to changing the tranny's neutral speed (same action that occurs during double clutching), then when you continue to pull the shifter into the next gear the synchro has to deal with a larger speed differential than it would if this hadn't occurred...
As far as the delay in revving, I have to believe this is purposely built into the ECU's logic for one reason or another... when I'm cruising at a steady 3000rpms and floor it the acceleration is instant... the tach moves up at the same time that my foot is going down... so mechanically, why would it be any slower to rev doing the same thing at a lower rpm? (although, I don't believe that *this* particular quirk of the drive by wire system effects the tranny in any way). Also, I've owned other drive by wire manual tranny cars (like a 5-speed IS300) and I never once even thought about the car being drive by wire. From my very first drive in this car I've always been conscious of the fact that it had a slightly unnatural feel, so I know the DBW operation is more exaggerated.
I don't know, I guess I'm still struggling with the idea that after 8 tranny revisions and numerous warranty swap-outs, Nissan just can't spec out a tranny that shifts reliably for a $30k+ car. That seems a bit hard to swallow. I have to think there is something else involved at least as a contributor, if not as the entire cause.
Jeff
As far as the tranny being able to do its job "no matter what the engine is doing" that's true to a point... it is the synchro's job to match the speeds, but obviously the greater the speed differential, the more work it has to do and the faster it will wear out... when you shift quickly, you are doing several things at once - letting off the gas, pushing in the clutch and pulling the shifter into the next gear... there will be a period there where you have only partially disengaged the clutch and yet you've already pulled out of the previous gear... at this point, more engine rpm amounts to changing the tranny's neutral speed (same action that occurs during double clutching), then when you continue to pull the shifter into the next gear the synchro has to deal with a larger speed differential than it would if this hadn't occurred...
As far as the delay in revving, I have to believe this is purposely built into the ECU's logic for one reason or another... when I'm cruising at a steady 3000rpms and floor it the acceleration is instant... the tach moves up at the same time that my foot is going down... so mechanically, why would it be any slower to rev doing the same thing at a lower rpm? (although, I don't believe that *this* particular quirk of the drive by wire system effects the tranny in any way). Also, I've owned other drive by wire manual tranny cars (like a 5-speed IS300) and I never once even thought about the car being drive by wire. From my very first drive in this car I've always been conscious of the fact that it had a slightly unnatural feel, so I know the DBW operation is more exaggerated.
I don't know, I guess I'm still struggling with the idea that after 8 tranny revisions and numerous warranty swap-outs, Nissan just can't spec out a tranny that shifts reliably for a $30k+ car. That seems a bit hard to swallow. I have to think there is something else involved at least as a contributor, if not as the entire cause.
Jeff
Reliability data above from 350Z owners. Compiled by Consumer Reports.
Valid statistics are difficult to find. Many 350Z drivers hold firm beliefs, and will not be dissuaded by facts.
