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914World.com _ 914World Garage _ First Gear Syncro and Dogtooth pics

Posted by: Joe Sharp Oct 17 2005, 09:27 PM

I took these pics because Las Vages Steve and I had a conversation about it.
First gear hub and syncro. What I'm looking for is the angle of the inteface between the syncro hub and the syncro band.

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Posted by: Joe Sharp Oct 17 2005, 09:29 PM

The ware aera is close to the split in the syncro band. As you can see the teeth match to the band.

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Posted by: Joe Sharp Oct 17 2005, 09:32 PM

The other side

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Posted by: Joe Sharp Oct 17 2005, 09:39 PM

In order for first gear to be engaged, the syncro has to go into the slider at least 6mm or about 1/4"
:PERMAGRIN: Joe

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Posted by: Joe Sharp Oct 17 2005, 09:44 PM

Steve had mentioned to me that he had a problem going into first gear and that the shifter felt that it was blocked going into first gear.
:PERMAGRIN: Joe

Posted by: LvSteveH Oct 17 2005, 11:28 PM

Nice pics Joe. Just for those who are wondering, I used a new first gear synchro/sider/dogteeth, and am having fussy 1st gear engagement.

The problem occurs when I'm at a stop light, out of gear, light turns, depress clutch, go for 1st gear. Half the time it goes in nice and smooth, the other have you have to re-clutch and pray. When it doesn't go, it's like hitting a wall, no indication of engagement. The clutch is properly adjusted and the 1st/reverse stack is not spinning as indicated by being able to go into non-synchronized reverse repeatedly with no issues. There is never any grinding, it's just hitting a wall trying to get into 1st about half the time. All new shift bushings of course.

The only thing I can think of is that I'm getting some kind of binding of the slider as it engages the synchro. I don't have enough miles on it to know if it will get better with time.

Joe was wondering if adding a chamfer to the slider would make initial engagement more predicable.

Posted by: Aaron Cox Oct 17 2005, 11:34 PM

QUOTE (LvSteveH @ Oct 17 2005, 10:28 PM)
Nice pics Joe. Just for those who are wondering, I used a new first gear synchro/sider/dogteeth, and am having fussy 1st gear engagement.

The problem occurs when I'm at a stop light, out of gear, light turns, depress clutch, go for 1st gear. Half the time it goes in nice and smooth, the other have you have to re-clutch and pray. When it doesn't go, it's like hitting a wall, no indication of engagement. The clutch is properly adjusted and the 1st/reverse stack is not spinning as indicated by being able to go into non-synchronized reverse repeatedly with no issues. There is never any grinding, it's just hitting a wall trying to get into 1st about half the time. All new shift bushings of course.

The only thing I can think of is that I'm getting some kind of binding of the slider as it engages the synchro. I don't have enough miles on it to know if it will get better with time.

Joe was wondering if adding a chamfer to the slider would make initial engagement more predicable.

same here. i always hit 2nd or third, then go for first......

Posted by: Twystd1 Oct 18 2005, 02:11 AM

It is my job to be the harbinger of bad news..

I took the job over from Aaron last month... He couldn't take it anymore.. Oh well...

Twystd1 :

Posted by: Joe Ricard Oct 18 2005, 04:52 AM

Those are some nice looking gear parts ya got there.

I only dressed up my 1st gear parts with a sharpening stone. no burrs etc. new synchro band. I get into gear about 95% of the time. Too much force just makes it worser.

Posted by: Red-Beard Oct 18 2005, 07:05 AM

You need to clean up the ridges inside the slots in the slider.

Posted by: fatlando Oct 18 2005, 08:51 AM

Are we stuck with these 901 thangs???

If money wasn't an issue couldn't machine shop build a better current one??

I'm just sore cuz mine is in pieces at the moment and have had no time to work on it....

plus driving the wifes neon sux!

Posted by: Paul Illick Oct 18 2005, 09:35 AM

QUOTE (fatlando @ Oct 18 2005, 06:51 AM)

plus driving the wifes neon sux!

She already knew that and is probably laughing her ass off to hear you say it.

...so what kind of new car are you going to get her?

Posted by: olav Oct 18 2005, 09:47 AM

The main reason for the "clunk" when slaming it into first gear at a stop light is because only the very tip of the synchro is used for first (when egaging from stop) because of the break band. The break band stops first from rotating after about 1/8 of a rotation.

The synchro engages firt gear and the brake band rotates as it rotates the band expands and stops the first gear dog teeth. At that point the slider engages and their respective positions aren't matched. Basically, there isn't enough time for first to spin up and it gets shut down by the break band.

When they aren't matched there is a "clunk"

Only first gear has a break band.

When you change from second to first you aren't allowing the break band to engage and the syncro is doing it's job of spinnig up first to the same speed as second (via the slider) and it goes in nicely.

Posted by: aircooledboy Oct 18 2005, 10:52 AM

It ain't just first gear, and it ain't just worn parts boys.

I'm driving my V8 w/ a tall geared 901. My 1st gear is your 2nd gear (I just don't use first), and my trany was just rebuilt top to bottom by the world famous Brad Meyuer. I have the exact same issue. Probably 4 outta 10 times, at a stop, trying to put it into gear is like hitting a wall. Going to 3rd first, then to 2nd works about 1/2 the time, but I just discovered in the last few days that reverse then 2nd seems to work every time.

What the cause is, I gots no freakin idear?

Posted by: lapuwali Oct 18 2005, 11:15 AM

QUOTE (olav @ Oct 18 2005, 07:47 AM)

Only first gear has a break band.

No. ALL of the gears have brake bands, and 1st only has ONE, where 2nd, 3rd, and 4th have TWO. One can only downshift into first, so first only needs to be "sped up". 2nd through 4th can be upshifted or downshifted into, so they need to be able to be sped up or slowed down. 5th can only be upshifted into, so it only needs to be slowed down.

Posted by: olav Oct 18 2005, 11:30 AM

QUOTE (lapuwali @ Oct 18 2005, 09:15 AM)

QUOTE (olav @ Oct 18 2005, 07:47 AM)

Only first gear has a break band.

No. ALL of the gears have brake bands, and 1st only has ONE, where 2nd, 3rd, and 4th have TWO. One can only downshift into first, so first only needs to be "sped up". 2nd through 4th can be upshifted or downshifted into, so they need to be able to be sped up or slowed down. 5th can only be upshifted into, so it only needs to be slowed down.

Ok, I knew first only had something unique about the break band but I couldn't quite remember. So, I'm glad someone else set it straight for the record.

Posted by: LvSteveH Nov 8 2005, 11:48 AM

Just thought I'd update, I now have around 2000 miles on the new first gear slider and synchro, and it is getting much better going into 1st gear the first time. It will still block it out once in a while, but now you can pull it in without reclutching. I think it's just a stiff synchro binding with the slider, and with time the synchro wears a bit and becomes more compliant.

Posted by: Bleyseng Nov 8 2005, 03:08 PM

QUOTE (LvSteveH @ Nov 8 2005, 10:48 AM)
Just thought I'd update, I now have around 2000 miles on the new first gear slider and synchro, and it is getting much better going into 1st gear the first time. It will still block it out once in a while, but now you can pull it in without reclutching. I think it's just a stiff synchro binding with the slider, and with time the synchro wears a bit and becomes more compliant.

This is typical with brand new parts as they have to wear in some!