911SC SKI

Currently having my 915 rebuilt

Mechanic wants to order new Bulk Rings
Parts shop is talking about Brake Bands and Spyders
This web forum, in the past, has talked about Sliders

Are Bulk Rings and Brake Bands the same thing? What the hell are Sliders?

I guess a little history might help too. Synchro into first was non existent and selecting second was notchy (especially coming back from 3rd) and required force. Mechanic stripped gearbox and found second gear to be missing a couple of teeth and first showing wear. He reports that all bearings etc appear in good shape.
At this stage, what is the minnimum I should be considering on ordering before putting back together?

Im at work in the desert at the moment and don't have my trusty Bentley Manual with me. Can anyone help shed a little light.

911SC SKI

art

They are actually called balk rings. That's the only part of this I can help with, but Im interested in the question.

Peter Zimmermann

1st speed on your car has a synchro ring, a brake band, an energizer block and an anchor block. It shares a slider with 2nd speed. Sliders are a large, thick, metal ring that contact the synchro ring of the gear being shifted into. The inside diameter of the slider matches the outside diameter of the synchro ring, and its machined surface acts together with the synchro's friction surface. The slider also has teeth that engage the "dog" teeth on each gear, thereby engaging that gear. 2nd thru 5th are slightly different, they each use two brake bands, an energizer and anchor. As a gear is selected the slider is moved into position against the synchro. The synchro is compressed and contacts the energizer, which pushes the brake band (which is anchored against its anchor) against the inside of the synchro ring. Think of old fashioned drum brakes that use two shoes per wheel. In this case the shoes are brake bands (2nd - 5th). 1st gear only needs one brake band because engagement is always the same. When the brake band stops the gear the slider teeth can mesh with the dog teeth on the gear. Any time that a synchro ring is replaced the slider must also be replaced. 1st/2nd share a slider, and 3rd/4th share a slider. New synchros must be measured after they are installed on each gear, the manual stipulates an acceptable range. Dog teeth wear/breakage determines if new dog teeth are necessary. The same for brake bands, anchors and energizers, every trans is different and requires different parts. The spyder is the part that locates each slider, and usually needs replacement only if one or more of its three teeth are chipped/broken. Regarding the term "bulk" rings, I've never heard that term used.

911SC SKI

Thanks Pete, you Rock!