non synchro'd reverse

[prove_it]

I got a japanese transmission and I took the end plate off and I noticed that reverse gear has no syncro plus it has an aluminum shift fork for 5/reverse. I was wondering does anyone know whick Japan model this trans came out of? I've put over 3000 miles on it with no problems so I know it has the same final drive ratio. Just curious if anyone knows what trans was built that way.

 

[The_Big_Weave]

Almost every manual transmission ever made does not have a syncro for Reverse.

 

[prove_it]

I'm pretty sure most of the W5M33 transmissions do.

 

[464/2K]

I'm going with the guy above you. They are straight cut gears so they just bind into eachother. That's why like 99% of the time when you wing it into R you get a nice grind. Also why it's super noisy when you get going 3mph+.

 

[jepherz]

Straight cut gears shouldn't have anything to do with synchros, but if you have synchros that means you're throwing it into that gear when traveling at speed? How often do you do that?

 

[NateCrisman]

Bingo. Reverse doesn't need a syncro because simply put, it should never be "entered" when there is any output shaft motion. The job of a trans syncro is to slow down the input shaft speed to match the output shaft speed which allows a clean tooth engagement. When exactly do you shift into reverse with the car already moving backward?

Reverse is straight cut gears simply because they are cheaper to make than helical gears. Helical gears hold more power and make less noise, but they take up more space and are far more expensive to make. This is reverse we are talking about...that should see no more than 1/4 throttle and 1500rpm..(whatever Tq that is). Who cares if it makes noise, you should be in reverse for all of 60 seconds.

 

So what we have learned today is that you shouldn't throw your car into reverse when cruising.

 

[donniekak]

All w5m33's have a reverse synchro. Take off the end case and you will see it on the end of the 5th gear hub/sleeve. It's not on the reverse gear itself, but instead acts on the input shaft. A w5m31 does not have a reverse synchro.

 

[grocery_getter]

Reverse gear does have a synchro but not it is not represented in the transmission in the customary way people think and talk about synchro. The reverse synchro is located at the the very end housing of the transmission as a means to take up the travel of the 5th/reverse shift fork when the linkage is moved into the reverse gear position. The reverse gear itself which is a gear that just turn the output rotation of the 1st gear doesn't have a synchro right on it like represented on the 1st-5th gears because as it is already mention by a few of the posts above, reverse gear isn't meant to be entered at speed so rpm matching is not a function that is needed to be achieved by putting a synchro adjacent to the gear in the customary way a synchro is usually installed.

 

[656of1000]

As far as I know, all W5M33's have aluminum forks. They have reverse synchros, too. The W5M31 from a GGSX has none, apparently.

 

[spoulson]

It is not a reverse synchro. It's called a reverse brake.

Synchro implies it needs to synchronize input/output. The brake simply slows down the input shaft as reverse gear shifts into place. Otherwise, suppose you just started the engine. Then, you quickly depress the clutch and shift into reverse. You find that it grinds then the gear goes in. The input shaft is still spinning even after disengaging the clutch. So, the reverse brake tries to stop it in time for the reverse idler to slide into place.

 

[464/2K]

Quoting jepherz:
Straight cut gears shouldn't have anything to do with synchros, but if you have synchros that means you're throwing it into that gear when traveling at speed? How often do you do that?



IIRC, straight cut gears=no syncors.

 

[prove_it]

great info going on here. I'm not talking about an actual syncro, it is the reverse brake as mentioned above. Both my stock GVR4s have one and so does my friends 96 talon. It may vary by model, but some do exist.

Now I really want to know what transmission I got in my car now. I had it in #1284 then put about 2000 miles on it before storing it. Put it back in and drove another 3000 miles.
I can't have a GSX trans because I have driven over 5000 miles on that trans with NO problems at all. If it were a GSX trans then my final drive ratios would be wrong. Correct me if I'm wrong but, I don't think I would never be able to drive 5000 miles with no problems if that were the case.
So what trans is this?
Has no reverse brake in the end housing.
Final gear ratios are the same as a GVR4.
Has no marking on it beside 255.

 

[jepherz]

Quoting 464/2K:
Quoting jepherz:
Straight cut gears shouldn't have anything to do with synchros, but if you have synchros that means you're throwing it into that gear when traveling at speed? How often do you do that?



IIRC, straight cut gears=no syncors.



Why does a synchro have anything to do with straight cut gears? Maybe there are aftermarket transmissions with straight cut gears that don't have synchros, but you could very well add them. Synchros help mesh the gears; straight cut gears vs heli. gears don't mesh any differently.

 

[iceman69510]

Quoting spoulson:
It is not a reverse synchro. It's called a reverse brake.




Bingo!

 

[464/2K]

k Jeff your, right and always will be. Sorry I tried to argue with the omega. /ubbthreads/images/graemlins/worthy.gif

 

[656of1000]

The trans number should be stamped at the top of the bell housing, near the shift cables. It will start out with W5M33..., or whichever, then a few more numbers.

And for the whole reverse synchro thing, I'm sure I was mis-using the term "synchro." When JNZ rebuilt my trans a few years ago, they gave me the option to replace the reverse "synchro," but it was wicked expensive, and not necessary, so I said no. That's where the term came into my head.

 

[autobahntom]

When needing to use reverse, push the clutch in, put the car in any other gear (I always use 2nd), then put it in reverse without taking your foot off the clutch. It will go right in without grinding. This works well on trans that don't have syncro's or reverse brake, etc.
Tom

 

[jepherz]

Quoting 464/2K:
k Jeff your, right and always will be. Sorry I tried to argue with the omega. /ubbthreads/images/graemlins/worthy.gif



Yeah, you put up one heck of an argument... /ubbthreads/images/graemlins/dunno.gif I simply asked a question; if you can't answer it, then I don't know what to tell you.

 

[prove_it]

so no one has any idea what trans is in my car?