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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Very hard shifting w/ AC on?



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      07-08-2012, 05:40 PM   #1
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Very hard shifting w/ AC on?

Whenever I have my AC on as the title states my 6mt shifts VERY hard in 1st ,2nd & 3rd almost a bog like feel but as soon as I turn my AC off the rough shifts are gone? Does anybody else experience this? It's very annoying!!!
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      07-08-2012, 06:36 PM   #2
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Absolutely no difference in shifting with A/C on or off in my early '07 E92 6MT...
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      07-08-2012, 06:47 PM   #3
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well its not harder in force to shift but yeah when the AC is on your engine is running harder so your rpms drop faster which in turn makes you have to throttle it more when you are rev matching.

you should always rev match as you are putting more wear and tear on your synchros if you dont.
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      07-08-2012, 07:39 PM   #4
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Quote:
Originally Posted by cleex024 View Post
well its not harder in force to shift but yeah when the AC is on your engine is running harder so your rpms drop faster which in turn makes you have to throttle it more when you are rev matching.

you should always rev match as you are putting more wear and tear on your synchros if you dont.
This is my first manual vehicle and to be honest I dont rev match ever. I'm going to start practicing again but I think my problem was when I started to attempt rev matching I was still basically in the learning curve of a manual and just found it easier not to. Now that driving a manual is fairly second nature to me i'm going to start rev matching every day until I master it. I love this car, more than any car i have ever owned, and i want to drive it as it should be driven. Thank you for the advice! I appreciate it
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      07-08-2012, 07:47 PM   #5
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Quote:
Originally Posted by JTracy223;122****1
This is my first manual vehicle and to be honest I dont rev match ever. I'm going to start practicing again but I think my problem was when I started to attempt rev matching I was still basically in the learning curve of a manual and just found it easier not to. Now that driving a manual is fairly second nature to me i'm going to start rev matching every day until I master it. I love this car, more than any car i have ever owned, and i want to drive it as it should be driven. Thank you for the advice! I appreciate it
no problem and also its better to over rev and wear out your clutch a little quicker than it is to wear out your synchros and having to replace that...i dont know if you can replace the synchros but it cant be cheaper than replacing your clutch 10k miles sooner. someone who has more knowledge on this can chime in.

also when you are trying to rev match just drive slower and try to get it right everytime instead of rushing it and dropping the clutch too soon...at least thats how i learned.
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      07-08-2012, 08:09 PM   #6
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Its definitely annoying to shift while the AC is on, the rpms drop so fast you have to shift quicker or rev match, I hate driving with the AC on, I agree op
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      07-08-2012, 09:40 PM   #7
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Yep, revs fall quicker due to AC's parasitic load. I either blip the throttle between gears, or short shift, i.e. 1-3, 2-4, etc.
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      07-08-2012, 10:11 PM   #8
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Quote:
Originally Posted by wonho
Yep, revs fall quicker due to AC's parasitic load. I either blip the throttle between gears, or short shift, i.e. 1-3, 2-4, etc.
Same here. It's a harder shift due to the load. Just account for it.
As for blowing the syncro's or gears in our trannies don't count on it happening. Our manual trans are Getrag's they are pretty insane and bullet proof. The clutch will wear 100 times over before the tranny unless your literally grinding gears. Then there's no hope for any tranny lol.
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      07-10-2012, 04:40 PM   #9
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Thanks for the replies guys.
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      07-10-2012, 05:01 PM   #10
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anyone other than me feel that shifting is actually easier with the AC on? the rpms drop faster so you don't have to wait ages between shifts especially 1-2....
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      07-10-2012, 05:29 PM   #11
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Quote:
Originally Posted by cleex024 View Post
no problem and also its better to over rev and wear out your clutch a little quicker than it is to wear out your synchros and having to replace that...i dont know if you can replace the synchros but it cant be cheaper than replacing your clutch 10k miles sooner. someone who has more knowledge on this can chime in.

also when you are trying to rev match just drive slower and try to get it right everytime instead of rushing it and dropping the clutch too soon...at least thats how i learned.
I honestly have to disagree, the synchros in BMW trannys have been known to be bullet proof except in a few models. It is bad in all aspects to over rev and slip the clutch between shifts whether it be upshifting or downshifting. It is bad for the flywheel, clutch, and the throwout bearing. When shifting you should never slip the clutch, the clutches true purpose is get the car started.
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      07-10-2012, 05:33 PM   #12
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Quote:
Originally Posted by jetblackcoupe
anyone other than me feel that shifting is actually easier with the AC on? the rpms drop faster so you don't have to wait ages between shifts especially 1-2....
I guess it depends how fast your used to shifting....sometimes faster shift results in more bog for me (but not always)

Agree with the poster above that with AC on RPM do indeed drop much quicker...glad to read your post great info
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      07-10-2012, 11:38 PM   #13
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i stalled today on a hill with my ac on... lol, first stall since i started driving 10 years ago.
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