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Posted by: F4i Apr 15 2004, 10:35 PM

This is a pic of my first gear slider. The dog teeth seem ok. What I am wondering about is the portion just rearward of the point. There seems to be some wear there. It could be machined that way I do not know. Should it be flat? Sorry for the bad description. It's difficult to describe. I know there are a few transmission gurus out there. Thanks


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Posted by: JOHNMAN Apr 16 2004, 12:23 AM

You asked for opinions.... So here goes....

In my opinion, I think there is a slight indentation in a new slider just as yours shows. As the slider compresses the "brake bands" they will "seat" in this indentation of the slider and help keep the slider engaged with the gearset.

I don't think you are seeing wear on yours. From my experience, the wear point is the tips of the teeth (or points). As these become more rounded, it becomes less easy to select the gear. Another wear item is the "brake band" itself. New they have an as-cast surface and as they wear, they become smooth. The function of the "brake bands" are to match the speed of the gearset and the slider through friction between the slider and the "brake band".

There you have my opinions.

Posted by: lapuwali Apr 16 2004, 12:51 AM

I think you're confusing synchros with brake bands. The synchro is the bit that matches the speeds, and it does indeed have a deliberately rough finish, to hold oil and essentially act like a fluid clutch. As they wear, they get smooth and a step forms in the band, so the clearance between the synchro and the teeth increases, and the speed matching stops working as well.

The brake bands are separate, and unique to the Porsche type synchros (as opposed to the Bendix-type synchros found on many other cars). You only downshift into first, so the brake band assembly is different on that gear.

Posted by: lmcchesney Apr 16 2004, 12:19 PM

What symptoms were you having?
Are not these dog teeth worn?
L. McCheseny

Posted by: F4i Apr 16 2004, 06:13 PM

It did seem tome that the indentation was there on purpose. I thought I would ask just to be safe. Do the dog teeth look worn? I thought they could go another round. As always opinions are welcome.

Posted by: JOHNMAN Apr 17 2004, 02:09 AM

lapuwali,

Damn, I knew that wasn't the right term, hence the massive use of quotation marks....

You sir are correct.

But I do believe the slider has that groove in there on purpose.

lmcchesney,

the teeth look ok, not great, but ok. There is some brass still down in the grooves (that is wear from the dog teeth on the gearset), but the slider looks servicable to me.

Posted by: bernbomb914 Apr 17 2004, 02:25 AM

could you rough up the synchro ring with the balls of a cylinder hone to improve their performance? I think that surface would help with the oil surface.

Bernie

Posted by: lapuwali Apr 17 2004, 08:56 AM

The surface is important, but so is the clearance between the ring and the teeth. Once the ring is worn, it needs to be replaced. Fortunately, only the first and second synchros need to be replaced in most gearboxes, since the upper gears don't usually get as much of a workout. Fourth and fifth generally last forever. Synchro rings are also only about $50 each. The first gear slider is nearly $400.