It could be pointed out that when reverse gear shares a common shift fork with 1st gear of 5th gear there may be a synchronizer hub/sleeve/and inserts but only a blocking (a.k.a synchronizer ring or brake shoe so to speak) on the 1st or 5th gear side of the hub. Reverse remains unsynchronized.
There is simply no good reason to synchronize a reverse gear assembly and if gear crunching is going on while trying to shift into reverse it’s not because of a synchronizer problem.
And there’s a good reason not to synchronize reverse - it greatly reduces the chance of accidentally engaging reverse while driving forward.
It could be pointed out that when reverse gear shares a common shift fork with 1st gear of 5th gear there may be a synchronizer hub/sleeve/and inserts but only a blocking (a.k.a synchronizer ring or brake shoe so to speak) on the 1st or 5th gear side of the hub. Reverse remains unsynchronized.
There is simply no good reason to synchronize a reverse gear assembly and if gear crunching is going on while trying to shift into reverse it’s not because of a synchronizer problem.
Exactly right, agree on all points
Back in the “Good Ole Days” when learning to drive I was taught to shift to reverse when parking, especially on a hill, because it was much less likiely that the transmission would jump out of engagement due to reverse requiring gears to become meshed rather than syncrhonizers being coupled.
And several transmissions had reverse and/or overdrive in the tail piece extension in the 1960s. The publics demand for 4 speed and later 5 speed transmissions with overdrive was filled by using 3 speed models already in production, relocating reverse and sometimes OD 5th. There was no lack of lubrication in that location.
The Big 3 took the quicker cheaper route on shifting also. The external linkage, even Hurst linkage was sorely lacking compared to the internal rail linkage used on heavy duty transmissions and most European models.
I know my 95 Nissan pickup doesn’t have a synchro for reverse.
Every once and a while, you can’t shift the transmission into reverse unless you shift into first, and just slightly move the vehicle forward.
Then it’ll go into reverse.
Tester
Ferrari 308 1st-neutral-reverse shift. Watch closely at the reverse-neutral shift at the end:
There’s something funky going on between the shift collar and the reverse gear.
I used to want a whatever you want to call it system going into reverse so the gears wouldn’t grind, when I was trying to rock the car out of a snowdrift. First, reverse, first, reverse, crunch, crunch.
Thanks for the interesting comments. I have to say I still don’t understand enough about how it is done I guess. I know a few things at least, for example that “synchro-mesh” isn’t the same thing as the synchronizer ring. And that there is an alternative method to using a synchronizer ring, but can’t remember right now what that alternative gadget is called. I think it has one syllable. In any event, is there a consensus here? Presuming when the Car Talk guys say “synchronizer” that it refers to a synchronizer ring, could the grinding noise when shifting into reverse on that Ferarri be caused by a worn out synchronizer?
...could the grinding noise when shifting into reverse on that Ferarri be caused by a worn out synchronizer?
I’d say, yes it could. To me, the little fingers I see disengaging between the shift collar and the reverse gear in my video could be some form of synchronizer. Whether T&R actually knew about Ferrari transmissions in this detail is, however, questionable.
They were probably wrong.
Worn synchronizers don’t cause clashing gears. Dragging clutches cause clashing gears.
Think about it. You have to be at a standstill to engage reverse regardless of how the gear is engaged, sliding gear or synchronizer. That means that the transmission’s output shaft is not moving. For there to be any clashing of gears something has to be moving, and the only thing left is the input shaft. If the clutch were disengaged it should be at a standstill too.
If you try to shift any manual transmission into reverse too quickly you stand a chance of clashing gears. The best way to ensure no grinding is to come to a standstill, step on the clutch, engage ANY forward gear (which will stop the input shaft’s rotation), then shift into reverse, all without letting the clutch engage. If you still get a grind the clutch is dragging and making the input shaft rotate as soon as you take it out of the forward gear.
A rough and dragging pilot bearing can also cause reverse gear gnashing due to the mainshaft turning instead of remaining stationary.
You have to be at a standstill to engage reverse regardless of how the gear is engaged, sliding gear orsynchronizerreverse clutch sleeve.
There, I corrected it for you.
...the only thing left is the input shaft. If the clutch were disengaged it should be at a standstill too, unless it is still coasting to a stop.
Ditto.
Since this post started with the question of whether a synchronizer is used on reverse gear in manual transmissions, and since I’ve gone into detail about how sometimes they are, I’ll respectfully decline your “correction”.
You have to be at a standstill to engage reverse regardless of how the gear is engaged, sliding gear or synchronizer.
As for your other addition, I’ll agree that if the transmission is put into reverse too quickly following clutch disengagement the input shaft will not have come to a full stop yet, and that can cause clashing. That’s the reason that putting the transmission into a forward gear first before reverse is the best practice, as I explained.
Clutch sleeve documentation:
;-]
I'll agree that if the transmission is put into reverse too quickly following clutch disengagement the input shaft will not have come to a full stop yet, and that can cause clashing because there's no reverse gear synchronizer.
Double ditto.
Persistent, aren’t you?
As I showed earlier, the entire sliding clutch collar, hub, blocking ring and guide assembly is sometimes refereed to as a synchronizer assembly.
You, too, seem hung up on the term synchronized versus the part named synchronizer. But, hey, if it makes you feel better Sunshine, call it anything you like.
Actually, quite a few cars do have a synchronizer for reverse:
Pull-quote:
Among the cars that have synchromesh in reverse are the 1995-2000 Ford Contour and Mercury Mystique, '00-'05 Chevrolet Cavalier, Mercedes 190 2.3-16, the V6 equipped Alfa Romeo GTV/Spider (916),[2] certain Chrysler, Jeep, and GM products which use the New Venture NV3500 and NV3550 units, the European Ford Sierra and Granada/Scorpio equipped with the MT75 gearbox, the Volvo 850, and almost all Lamborghinis, Hondas and BMWs.
Worn synchronizers don't cause clashing gears. Dragging clutches cause clashing gears.
Ever try to shift a 1963 Dodge 383CI w/3-spd manual from 1st to 2nd with a worn out 1-2 synchro? Clash city.
Sunshine
In my research, I haven’t seen many transmissions with a synchonizer for Reverse. Even the transmissions which use a sliding dog clutch sleeve rarely have a blocking/baulk ring in front of the dog teethof the gear.
Now the question to answer is why Reverse is rarely synchronized. My thinking is that Reverse engagement is prohibited when moving forward by the awful sound of the clashing. Can you imagine the mayhem that would result if you got into Reverse at a substantial forward speed and released the clutch with the drive disk spinning counter to the engine flywheel and pressure plate. Something would probably fail i.e. drive train, transmission, clutch disk, drive shaft, etc.
Thanks @researcher, yes, your post reminds me, that’s it, “baulk ring”. That was the word I was trying to remember before. I’m not sure if a synchro-ring and a balk-ring are two different names for the same gadget, or two different methods to accomplish the same function.
Years ago my dad’s 1960’s Ford truck had a 4 speed manual transmission, but when driving around town you only used the top 3 of the gears, which were all synchro-mesh. I think they were labeled on the gear shifter C, 1, 2 ,3 … C for “compound”. C was a really low gear, like for going up a really steep and rocky dirt road, and not synchronized. You couldn’t get into C without grinding the gears unless your were completely stopped or you downshifted and perfectly double-clutched.