question for those that have FI

m4a1mustang · 01-13-2012, 09:54 AM

Quote:

Originally Posted by phunk

Skipping gears is hell on your synchros. It worked before because they were fresh, it doesnt work now because you are wearing them out. Pretty soon you will have trouble shifting into 6th at all without double clutching. Many dealers will reject warrenty replacement of transmission with synchros problems if they find you skip shift gears... they would know because someone might complain that they are no longer able to do so, or they will ask you to take them on a drive to show them the problem, but they are also observing how you drive.

If you are hell-bent on continuing to skip shift 3rd to 6th, instead of depending on whats probably a single brass synchro for 6th to slow the mainshaft down by so much for such a change in ratios, just double clutch it and you are removing most the burden of the synchros. double clutching takes more time but if your skipping 3-6 then you arent racing anyway.

ALSO i would like to add that I am not a transmission builder, so my terminology shouldnt be quoted or used for debate and i will gladly take a seat on this topic to a transmission expert... i am just explaining it the best that I can based on the little i know about one aspect of cars/performance that i have rather avoided learning the deep inner-workings of.

If skipping shifts was so bad on your synchros then manufacturers wouldn't force features like "skip-shift" that make you go from 1-4 in easy driving.

phunk · 01-14-2012, 05:40 AM

Quote:

Originally Posted by m4a1mustang

If skipping shifts was so bad on your synchros then manufacturers wouldn't force features like "skip-shift" that make you go from 1-4 in easy driving.

You are ignoring the many separations in the scenarios. High torque large displacement vehicles use a 1-4 skip shift solenoid for gas mileage only. The skip shift solenoid engages at low load and low rpm only, and the speed changes are less drastic. 3-6 is a taller shift and the OP is shifting out at a pretty high rpm and probably not waiting for the engine speed to come all the way down either. Not to mention lower gears use more robust double or triple synchros depending on exactly which transmission and gear. 6th is a single for pretty much every trans. There is a reason his 6th gear is not continuing to allow it... And when something performs worse over time in a vehicle, that is due to wear.... And I guarantee you that wear is in the transmission... Not a side effect of turbos or anything.

Btw I skip shift pretty often myself. I wait for the engine speed to come down before attempting. To do so should help a lot versus shifting it at a "normal" rate. It had never destroyed a trans on me but my 350z did eventually become rather difficult to get into 6th without perfect timing.. But it was 5th that really got beat up because that's the gear I usually skip shift into if I'm going to skip. 5th gear synchros pretty much toast in my 350z by the time I sold it this year.

m4a1mustang · 01-14-2012, 08:07 AM

Ah, I thought you were generalizing all skipped shifts as "bad". If you skip shifts right and match your revs that shouldn't cause excessive wear.

Zat_Zuma · 01-14-2012, 09:40 AM

In the old 350Z's downshifting was difficult on the transmissions. (no SRM back then) Double clutching and rev matching helped the syncros get up to speed, so to speak, and I never had a problem with upshifting or downshifting when I double clutched. Smooth as silk when everything, in the transmission, is running to match the engine RPM.

phunk · 01-14-2012, 04:33 PM

Quote:

Originally Posted by m4a1mustang

Ah, I thought you were generalizing all skipped shifts as "bad". If you skip shifts right and match your revs that shouldn't cause excessive wear.

ya id say yes and no... theres 20 different ways to skip a shift and some are going to increase wear a lot and some are going to be marginal... i would say that you can figure on some sort of increased wear, more/less depending on exactly how you drive. Its a good thing to have a little understanding of, if its in your practice, then you can prevent premature wear.

the good news is that a new transmission is under $2000 for this car... thats less than a good clutch/flywheel kit. Installation is only a couple hours of monkey work. Spread out over a 6-7 year span (just going by my 350z trans) that it should still be useable and tolerable under abuse... thats probably less money than you will spend on brakes. so its a wear item, i say wear it out. replace it when its no longer adequate. just cant complain if they dont work like new for the life of the vehicle under abused circumstances.

Blackcrimzon · 01-15-2012, 06:32 AM

Thanks for all the impute. I don't skip gears all the time. Just once in a while when I'm getting on the highway. Though from what I read its not good to have that much of a difference between your engine speed and trans speed. I knew that but never thought about it when skipping gears. Well I'm just not going to do it anymore. And just a side note I do drive in 6th anytime I'm going over 33mph to save on gas.

01-14-2012, 08:07 AM	#18 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6962	Ah, I thought you were generalizing all skipped shifts as "bad". If you skip shifts right and match your revs that shouldn't cause excessive wear. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook! Last edited by m4a1mustang; 01-14-2012 at 08:09 AM.

01-14-2012, 09:40 AM	#19 (permalink)
Zat_Zuma A True Z Fanatic Join Date: Nov 2008 Location: Edmonton, Alberta ...eh Posts: 1,171 Drives: 2017 Touring auto Rep Power: 19	In the old 350Z's downshifting was difficult on the transmissions. (no SRM back then) Double clutching and rev matching helped the syncros get up to speed, so to speak, and I never had a problem with upshifting or downshifting when I double clutched. Smooth as silk when everything, in the transmission, is running to match the engine RPM. __________________ [B]2009 & 2017 370Z Touring Sport Autos SOLD

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01-15-2012, 06:32 AM	#21 (permalink)
Blackcrimzon Base Member Join Date: Jan 2009 Location: AZ Age: 42 Posts: 190 Drives: Nismo 370z 09 Rep Power: 16	Thanks for all the impute. I don't skip gears all the time. Just once in a while when I'm getting on the highway. Though from what I read its not good to have that much of a difference between your engine speed and trans speed. I knew that but never thought about it when skipping gears. Well I'm just not going to do it anymore. And just a side note I do drive in 6th anytime I'm going over 33mph to save on gas.