5th gear synchronizer
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This is a discussion on 5th gear synchronizer within the Maintenance, service, and repair forums, part of the Tutorials & DIY category; WRX 2011, 40k miles. Almost since birth has this problem: if I get to 60-70mph, switch to neutral, let RPMs ...

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    5th gear synchronizer

    WRX 2011, 40k miles. Almost since birth has this problem: if I get to 60-70mph, switch to neutral, let RPMs go to idle, then try to engage 5th - it grinds. Dealer replaced oil first, then replaced synchronizer. Helped for ~200mi, then same thing again. Now they say that local service rep claims it is by design, and I should engage 4th - will be fine. It is fine, I can get 4th or 3rd; it grinds only on 5th. But it doesn't make sense to me.

    Does anybody else have this issue? And yes, I know you should stay in gear; I just have this 3 mi long hill going home

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    Registered User Obeisance's Avatar
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    Quote Originally Posted by melizarov View Post
    if I get to 60-70mph, switch to neutral, let RPMs go to idle, then try to engage 5th - it grinds.
    As I understand, The synchro's job is to help bring the transmission speed to match that of the engine (and vice versa). The three components (engine, flywheel?, and driveline) can move at different speeds. You have gauges showing the engine speed and the transmission/road speed, but the flywheel (or clutch, since I'm not sure which end is on the transmission) speed could be very different from either of these if not coupled to either (to the engine via clutch pressure or to the transmission via being in gear). Thus, if they are at very different speeds and the gear is forced too much (I expect that there is some force threshold below which you would not get grinding), it does not surprise me that there is grinding (similar things happen if coasting fast with the clutch disengaged and trying to put the transmission into first). This could me mitigated by double clutching to rev-match the shift.


    Quote Originally Posted by melizarov View Post
    And yes, I know you should stay in gear; I just have this 3 mi long hill going home
    I won't comment on the safety of coasting down a hill in neutral (and why the lack of being able to quickly get back into gear due to the grinding is a prime example), however I would like to say that if you leave the car in gear with the clutch engaged when coasting, the fuel injectors shut off until the engine reaches an rpm near/below the idle point. Thus, if you coast in gear you don't use any fuel.
    David - '05 WRX

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    Quote Originally Posted by Obeisance View Post
    As I understand, The synchro's job is to help bring the transmission speed to match that of the engine (and vice versa).
    Absolutely. However, if you think of it - 5th gear wheels spin slowest, 4th are higher and 3rd even more. And I can engage 4th and 3rd w/o any noise. In fact, I took dealer's tech on a ride and he agreed that there is a problem with synchronizer. So my question was more along the line - does anyone else has similar issue, and do you think this is something that should be covered by warranty.



    Quote Originally Posted by Obeisance View Post
    I won't comment on the safety of coasting down a hill in neutral.
    I know… I have weird driving history - let's say first 10+ years it was carb, no injectors…

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    Registered User SKI.WRX's Avatar
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    The half shaft on the transmission is likely completely stopped at the bottom of a three mile long hill. You are grinding because like said above you are forcing it into gear before the synchro has time to bring the half-shaft back up to speed. Hold the shifter against the gate lightly and it will eventually fall into gear.

    And again just leave it in gear, you will use less gas because fuel injected motors engage Decceleration Fuel Cutoff under closed throttle and low load conditions, your 5th gear synchro will last longer, and it is safer.

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    Registered User Soobvirgin's Avatar
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    I've only ever owned manual cars and I used to sell cars for 4 years too. So, I've got plenty of experience with manual transmissions... well, driving them, at least. The 'box in my 2012 WRX is the worst of any new car I've ever driven. Even after 2 years, when you'd expect it to have worn in a little, it still takes far too much pressure to put into each gear. Plus, I have to wait momentarily before things line up, otherwise I'll get grinding. And yes, 5th gear is the worst. The synchro was replaced within the first year of ownership and I was told the rest of the gears felt ok. I can only assume the tech either doesn't have experience with manuals and no frame of reference to know that it's NOT ok, or knows all WRX boxes are like this.

    After they replaced my 5th gear synchro, it felt exactly the same. The only difference being that it was now harder to get into 3rd as well. After another year, it now feels like it's getting worse, so I'm having them drive it again when I take it in for a service next week. It completely ruins the driving experience for me because I'm constantly aware that I need to baby the 'box. Fast changes simply aren't happening.

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    OK, here's my conclusion.

    All comments about staying in gear are right. As well as how to get it into 5th w/o grind - this is exactly what I do. As well as about fuel economy. Getting into gear upshifting is not a problem, always smooth. Giving it a bit of gas also solves grinding issue, so all make sense.

    However, having said all this. Still doesn't make any sense to me that I can get into 4th (or 3rd) easy, and 5th - nop. I do believe that there is a design issue with the 5 speed gearbox. I don't think dealership will acknowledge this unless there is lots of outcry.

    @Soobvirgin - I guess I was more lucky than you - 3rd was not affected. I feel your pain, bro. And I'd say speed of shifting is not important when we're talking about 5th - if you're in 5th you either try to save fuel (and thus speed is less important), or going 120+… So yes, I agree that the defect sucks, but it doesn't take that much from overall driving experience. I still love my car.

    Basically, I low what I'm doing "wrong". Reason have stared the thread is to find out if there are other WRX owners out there having "not as positive as expected" experience with 5th gear synchros. As mentioned above, I believe this design defect. I think it should be covered by warranty. Dealership - and through it local Subaru - disagree.

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    Registered User Soobvirgin's Avatar
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    Quote Originally Posted by melizarov View Post
    @Soobvirgin - I guess I was more lucky than you - 3rd was not affected. I feel your pain, bro. And I'd say speed of shifting is not important when we're talking about 5th - if you're in 5th you either try to save fuel (and thus speed is less important), or going 120+… So yes, I agree that the defect sucks, but it doesn't take that much from overall driving experience. I still love my car.
    Oh, yes, I completely agree that if you're shifting up into 5th then you're not in a hurry. My problem is that I can't rush any gear. I have to wait for the synchros to sort themselves out before I can change into any gear. It's not a long pause, but there shouldn't be any pause at all. I find it incredibly frustrating. Also, regarding your specific problem, between the cars I've owned and the numerous company cars, I've never had one that wouldn't let me shift into neutral and back into 5th at speed (not that I had cause to do that very often). It's not normal. I don't care what the speed, as long as the clutch is depressed, you should be able to shift into any gear but 1st and reverse.

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    Registered User Soobvirgin's Avatar
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    I took my car in for a service on Monday and I went for a ride with a technician who drove my car to test the 'box. He thought it seemed completely normal, even 5th gear. I asked him if he thought it was normal just for WRXs or normal for all manual cars. He replied that it seemed normal for other manuals he'd driven that weren't Subarus. I left it at that because nothing I said was going to change his opinion. But he's flat out wrong. I've never experienced a new car with such a notchy gearbox. Oh well, I'm 2 years into a 5yr finance deal and I'm looking forward to our time together being done. Not sure what I'll go for next but, it never rains here, so I don't need AWD. It'll take Subaru doing something special for me to get another.

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