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I used to have a Renault Laguna (model year 2000) until I got a Volvo V70 (model year 2006) to replace it. One of the things that annoyed me somewhat about the Renault was that, if I was e.g. approaching a red light, I couldn't "pre-shift" into first gear from any higher gear before the car had come to a full stop or possibly very close to a full stop, even if I knew for a fact that I would need first gear going forward. (Note: I sold the Renault several years ago, so the exact details are slightly hazy. However, the general gist is correct.)

Now, I understand why I wouldn't be able to shift normally into a different gear while the car is moving without disconnecting the engine from the rest of the drive train by depressing the clutch pedal. That makes sense given even what little I know about cars, and is not what I'm asking about here.

Rather, I am curious why the Renault wanted me to bring the car to a full stop before I could shift normally into first gear specifically. (I don't think I ever tried it with reverse, and don't recall ever having any difficulty shifting into any gear.)

Volvo obviously managed to make the same thing work a few years later, and it doesn't seem like rocket science. After all, it's a required feature for all other forward gears to be able to shift into them while the car is moving, and a model year 2000 car is hardly an antique.

Is the Volvo lacking some protective mechanism that the Renault had (in other words, it's a kind of safety feature of the Renault, to prevent shifting into first gear at wildly inappropriate speeds whereas Volvo decided to trust the driver), or does the Volvo have something that the Renault didn't (which enables shifting into first gear while the car is moving)? What is the specific difference that could describe this behavior?

  • Driving schools tend to teach you not to shift into first unless you are completely stopped. Saying that, I think that model Renault does actually have a synchro first gear. Its all down to driving experience, I drive a lot of new and old cars, a lot of them aren't happy going into first whilst moving. – DizzyFool Nov 24 '16 at 9:05
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I suspect your Volvo has a Synchromesh on first gear, and the Renault didn't. Synchromesh (or Synchro) is the mechanism that allows the speed of the gearbox shafts to quickly change to match each other as you change gear, allowing you to change quickly and easily without having to 'double-declutch' (press the clutch, change out of gear, release it, press again to change into the next gear).

It's been a common feature of most cars since the 1960's, but many cars did not have it on first or reverse gears, in order to reduce cost - as you're almost always stopped when you select these gears, it was't considered necessary. Newer and higher-end cars (such as Volvos) have it though, as cost is less of an issue on higher-spec cars, and people expect them to be more refined.

  • So you're essentially saying that synchros are per-gear, and the Renault likely didn't have one on first gear? I suppose that makes sense. – a CVn Oct 21 '16 at 17:23
  • Yep, that's it. – Nick C Oct 22 '16 at 16:47
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I think Nick C "hit the nail on the head". Volvo's are high-end, well-engineered cars while Renaults are more "basic transportation" Many, many cars have synchromesh on all gears but it seems your Renault did not.

  • Please can you elaborate on what makes Renault "basic transportation"? I am looking for a source to confirm that the Renault does actually have a synchro on first gear. – DizzyFool Nov 24 '16 at 9:02
  • Well, all I meant by that statement is that Volvos are known to be well-engineered and somewhat expensive cars while Renaults are often considered more ordinary cars. I am not passing any judgment, just observing that Renaults are to Volvos as Chevys are to Cadillacs - both are perfectly fine automobiles but are in different price points due to engineering & equipment differences. – CarCrazyBen Dec 5 '16 at 17:30
  • What is the relevance? Having owned this exact model and wrenched on it I can confirm it has a synchro first gear. I just need to find a source online to share here. – DizzyFool Dec 7 '16 at 22:15

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