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This is a discussion on downshifting is bad for tranny? within the Transmission & AWD forums, part of the Tech & Modifying & General Repairs category; yes you should rev match although the reason we have syncros(or syncromesh) nowadays is so you don't really have to ...

  1. #16
    Registered User big_sur's Avatar
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    yes you should rev match although the reason we have syncros(or syncromesh) nowadays is so you don't really have to double clutch unless you just feel an overwhelming urge(or your dumbass can't shift in the first place and wore out your syncros in which case you're probably screwed anyways), no you should not roll around out of gear using your brakes all the time as that's pretty much retarded. it's a car, not a small baby, treat it as such.

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  3. #17
    Moderator YBNormal07's Avatar
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    I think we need a sementics/clarity check here.

    In a modern car, downshifting hurts nothing.

    In a modern car, POOR shifting hurts everything associated with the drivetrain.

    In our AWD cars, the less shock you give the drivetrain, the happier all of the parts are.

    This is true for upshifting and downshifting. As long as you are not visciously popping the clutch when shifting up or down, and as long as you are not having to force the shift lever into gear, you are not abusing or hurting your car.

    Double clutching is not necessary in our cars and in fact, when racing, will slow you down. Rev matching is nice, but not a necessity. I do it on road coarses but for everyday driving...nope...(feets are too big).

    Using the transmission to help slow the car down (engine compression braking) does not hurt the trans. It puts more wear on the clutch, but again, as long as you aren't just letting the clutch pop out, it will last forever.

    A decent trans shop or the dealer can tell right away if your synchros are worn.
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  4. #18
    Administrator Trainrex's Avatar
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    Quote Originally Posted by YBNormal07 View Post

    Using the transmission to help slow the car down (engine compression braking) does not hurt the trans. It puts more wear on the clutch, but again, as long as you aren't just letting the clutch pop out, it will last forever.
    Just to clarify, engine braking doesn't hurt the clutch, dragging to clutch to slow down does. Once the clutch is engaged, nothing is damaged. Rev matching is the key.

  5. #19
    Moderator YBNormal07's Avatar
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    Quote Originally Posted by Trainrex View Post
    Just to clarify, engine braking doesn't hurt the clutch, dragging to clutch to slow down does. Once the clutch is engaged, nothing is damaged. Rev matching is the key.
    Agreed. For me, downshifting involves full disengagement of the clutch...no "clutch breaking". Rev matching is the key...or you can simply wait until the rpms's drop down to a comfortable level. I do blip the throttle when downshifting, but I am not trying to actually rev match (even though I guess this is rev matching by definition). I think of rev matching as more of a track application as I am screaming down from high speeds. For everyday driving, my downshifting occurs near my stop, so rev-matching isn't a concern.
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  6. #20
    Registered User ezzzey's Avatar
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    Quote Originally Posted by subarutech View Post
    checking you synchros requirs a complete tranny break down.. looking at alot of money at least the 700 mark prob more like 900 depending on where you bring it..and yes down shifting is bad if its not done properly..your synchros and gears get clashed together causing not normal stress on the internals..one of the reasons you see alot of wrx tranny's gone bad...what makes you think you need to check your synchros?
    few months back my 3rd gear started grinding after a 3.5krpm's... so i changed tranny fluid to REDLINE MT-90 and 3 days later it was gone and it has never come back since.. Someone on the forum said i should go get my syn checked, because in a year my tranny can go bye bye!!?!?!

  7. #21
    Registered User HLxDrummer's Avatar
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    Just throwing the shifter down a gear and slipping the clutch wears the clutch as well as the synchros. This is because the clutch is making up the difference in speed between the input shaft of the transmission and the engine. This is also because the synchros are making up for the difference in speed between input and output shafts of the transmission.

    Rev-matching (throwing it down a gear, and giving the engine throttle as you let out the clutch) will only wear the synchros when performed correctly. This is because when you give the engine throttle as you let out the clutch, you are manually matching the speeds between the input shaft of the transmission and the engine instead of the clutch making up for the difference. This is also because the synchros are still making up for the difference in speed between the input and output shafts of the transmission.

    Double-clutching (clutch in, neutral, clutch out, rev, clutch in, put in gear, clutch out) will not wear the clutch or synchros when done properly. This is because when you put the transmission in neutral and rev, it is speeding up all the gears/shafts/etc. in the transmission as well as the motor so when you put it in gear everything in at the right speed. When done correctly the shifter will just slide into place.

    On older cars without synchros you had to double clutch, but on today's cars it is not needed, but will help preserve the synchronizer's life.

  8. #22
    Registered User ezzzey's Avatar
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    double clutching ftw!!!

  9. #23
    Registered User Slider's Avatar
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    I just put the car in the correct gear and blip the throttle to get the RPMs up so when i let the clutch out it doesn't put so much strain on it.
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  10. #24
    Registered User mike05STi's Avatar
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    Quote Originally Posted by TheJ View Post


    Sophie the tranny says "it's all about moderation".
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  11. #25
    Registered User jaqattack02's Avatar
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    Double clutching may be a little bit better for the transmission, but the couple times I tried it it's just so much slower I just can't see where it's worth it. Obviously they put the synchronizers in there specifically so you don't have to do that, so I would certainly hope they were built to hold up to regular downshifting.
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  12. #26
    Moderator YBNormal07's Avatar
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    Quote Originally Posted by jaqattack02 View Post
    Obviously they put the synchronizers in there specifically so you don't have to do that, so I would certainly hope they were built to hold up to regular downshifting.
    They are.
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  13. #27
    Registered User 05silverWRX's Avatar
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    It's better not to downshift or upshift. Just leave it in 3rd. It is the universal gear. That way you only have to replace your clutch.
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  14. #28
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    never learned how to double-clutch, but I was trying to learn heel-toe on my old RX-7 before the engine died, the few times i managed to pull it off, it felt good down shifting. No major disturbance in the drivetrain, but it was a pain in the ass to do.

    agreed on the idea of replacing brakes over trannies though.
    I would also prefer not to start out with "sophie the tranny" in my subie when i get one haha.

  15. #29
    Registered User gimme_cat's Avatar
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    Proper double-clutching/rev-match technique is all in the shoes. Loafers and dedicated driving shoes are good for pedal work. Barefoot is best.
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  16. #30
    Moderator schischwein's Avatar
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    Proper double clutching downshifts(obviously with rev matching) is technically not any slower than simple rev matching or slipping the clutch.

    The time required for the rotation speeds to match for the latter two account for the extra set of clutching out in neutral and blipping. When done properly, it is very fast. When you simply rev match, you would have engaged your clutch, but the syncros are still working at matching up. You aren't any faster than proper double clutching.

    Driving bare foot is usually not a great idea. While good for sensation, your foot is unsupported where needed. Proper driving shoes would be ideal, but thin soled, supportive shoes work. Rounded heels are a good idea as well.

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