Volkswagen Passat Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #1
Hi there thanks for all that make this forum my goto tool when facing issues with my 2004 B5. Currently at 195k and have started experiencing a grind in manual transmission 2nd gear on upshift and downshift. Based on searches it appears I may have bad synchro. Some posts reference a term that I am unfamiliar with "Rev shifting" as a potential way to eliminate grinding short of having tranny repaired. Trying to avoid that as I only need the car to last me a few more months until I put her out to pasture. Can someone explain to me what Rev shifting is? Thanks in advance!
 

·
Administrator
Joined
·
23,555 Posts
Rev Matching. You bring the RPM up to roughly what it would be when engaging that gear. Helps it go into gear easier since the output shaft and trans input shaft are spinning the same speed. Change your fluid every 60k or so. How old is the trans oil in there now?

To quote a Porsche driving instructor:
"Rev matching will save the wear on your synchronizers, and make gear changes smoother. It will also reduce wear on your clutch and reduce stress on the gearbox, and drive train as a whole. Most upshifts do not require rev matching, but downshifts should be rev matched.
You may have noticed: when you drag the gear lever into a lower gear from higher speed (with the clutch pedal pressed and the engine rpm at idle) there is a tiny “whine” sound from the gear box. That is the synchronizers working hard to facilitate the shift. The harder you make them work the faster they wear out and then eventually they will no longer help you. You can nearly eliminate synchronizer wear by using a technique called double clutching, or double de-clutching if you're from UK. This technique involves the following process:
1)clutch depression
2)pull gear lever into neutral
3)release clutch pedal in neutral, and SIMULTANEOUSLY rev the engine to slightly exceed wheel speed for the next gear you will choose.
4)depress the clutch pedal and immediately slip the gear lever into the chosen gear
5) If you’re coordinated… you’ll release the clutch pedal again while the engine speed and gear chosen are perfectly matched.
If you had no synchronizers in the gearbox you would need to do the above for every downshift, or you will hear and feel a “crunch” as you smack the gears together because they are traveling at such disparate speeds.
Rev matching alone…without double clutching, will have an effect of reducing clutch and gear wear, but it becomes more important to make sure that you've reduced the vehicle speed to what is appropriate for the gear you are selecting before moving the lever into the lower gear. Shifting into a gear too low for the speed the vehicle is traveling, even with the clutch depressed, will cause premature wear of the synchronizers. I’ve driven several student cars at various performance driving schools with synchronizers abused and rendered useless. Some students have brought cars in saying “It won't go into second gear.” I’ve taken the car out to check what is going on, and find that it shifts perfectly fine into second gear…but not when you neglect to rev match and double clutch."
 

·
Registered
Joined
·
15 Posts
Discussion Starter #3
Thanks VAGguy for the quick response and correcting my terminology. You say typically not needed when upshifting but this is when I would most like to Rev Match in order to avoid 2nd gear grind. Appreciate the detail you've provided, would the procedure be similar for upshifting? I'm currently reving 1st gear a bit higher than normal and skipping 2nd straight into 3rd. Not sure what long-term affect that will have on the transmission.
 

·
Registered
Joined
·
26,602 Posts
It was originally called double clutching as cars did not have syncros, so you had to do all of the time. I was taught how on tractor trailers as none of our trucks had syncros.
 

·
Registered
Joined
·
992 Posts
Personally, I rarely down-shift into second (or first!) gear, at least in a Passat. 4-wheeling or something might be a different story but in that case I'd use the brakes first to get the car slowed down before engaging the gears. At those lowe speeds I just use the brakes. As for the effect of shifting from 1st to 3rd, I'd say it will probably wear the clutch more than anything as I assume you will need to feather the clutch a bit when engaging 3rd gear.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #7
Personally, I rarely down-shift into second (or first!) gear, at least in a Passat. 4-wheeling or something might be a different story but in that case I'd use the brakes first to get the car slowed down before engaging the gears. At those lowe speeds I just use the brakes. As for the effect of shifting from 1st to 3rd, I'd say it will probably wear the clutch more than anything as I assume you will need to feather the clutch a bit when engaging 3rd gear.
Thank you Iowegian! Hopefully the extra clutch wear isn't too excessive and will last me until springtime. It's a shame as the car looks and runs great (195k) except for this 2nd gear issue.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #8
It was originally called double clutching as cars did not have syncros, so you had to do all of the time. I was taught how on tractor trailers as none of our trucks had syncros.
Thank you ar393 for clarifying!
 

·
in dire need of an organic chemistry lesson
Joined
·
2,327 Posts
Personally, I never down-shift into second (or first!) gear, at least in a Passat. I'd use the brakes first to get the car slowed down before engaging the gears.
Even if you brake the down gear shift happens anyway. So what is the difference in terms of wear and tear?
 

·
in dire need of an organic chemistry lesson
Joined
·
2,327 Posts
The OP has a manual transmission.
With the manual one sometimes quick down shifting gears to slow down is not a bad practice if there is not enough time/space for brake to operate. But I agree it should not become a habit; albeit I do that often myself with my tiptron.
 

·
Registered
Joined
·
7 Posts
Hi there thanks for all that make this forum my goto tool when facing issues with my 2004 B5. Currently at 195k and have started experiencing a grind in manual transmission 2nd gear on upshift and downshift. Based on searches it appears I may have bad synchro. Some posts reference a term that I am unfamiliar with "Rev shifting" as a potential way to eliminate grinding short of having tranny repaired. Trying to avoid that as I only need the car to last me a few more months until I put her out to pasture. Can someone explain to me what Rev shifting is? Thanks in advance!
Hi there thanks for all that make this forum my goto tool when facing issues with my 2004 B5. Currently at 195k and have started experiencing a grind in manual transmission 2nd gear on upshift and downshift. Based on searches it appears I may have bad synchro. Some posts reference a term that I am unfamiliar with "Rev shifting" as a potential way to eliminate grinding short of having tranny repaired. Trying to avoid that as I only need the car to last me a few more months until I put her out to pasture. Can someone explain to me what Rev shifting is? Thanks in advance!
Out of curioisity - when was the last time the manual gearbox oil was drained and replaced? If the oil is old (gummy) and low, it can also cause the synchros to not spin as needed to ease shifting. I bought several quarts for the Jetta but then sold the car. I think it is Royal Purple manual gearbox oil, you need a pump to fill through the upper access hole or barring that, an assistant to pour into an elevated funnel while the person below keeps the hose inserted and watches for the overflow when full.
 
1 - 16 of 16 Posts
Top