Seems unlikely on a car, but 附板 seems to mean the gear that engages with the chain in a chain drive system.

应该是说挡泥板吧？？

1. The definition of 附板 is something that is fitted onto a conveyor chain. It has holes to support or attach other attachments and looks like this: http://img2.cn.china.cn/2/0_113_29577.jpg

“顾名思义，既是附板，那就是普通链条没有，另外附加上去的东西。这附板孔，是在附板上制作，可以把它和别的器件连接的孔。譬如，在下面的图中的滚子链，每节链条都带着块折弯的板，板上面有两个孔，这就是带附板链条。孔，当然就是“附板孔”了。”

Source: http://bbs.cmiw.cn/forum.php?mod=viewthread&tid=251279
2. 带配件 (Attachment) 小型输送链: http://chunben.com/power-transmission/small-pitch-conveyor-c...
3. 短节距附件 (Attachment) 链条: http://www.dgdgo.com/products_content-298368.html
4. The pictures and concepts explained above correspond with the chain attachments shown in these English websites:
http://www.eriks.co.uk/Attachment-Chain/431
http://www.cross-morse.co.uk/pdf/Chain AttachmentsEN.pdf : “British standard roller chain attachments: The attachments below are available on 72 hour service built into the base roller chain at spacings to suit the application, K & M attachments can be fitted to only one side of the chain or both sides (as illustrated). Attachments of different types can be fitted in one chain assembly. “
I hope this helps!


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Note added at 2 days3 hrs (2013-09-21 05:37:17 GMT)
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That said, I can't be absolutely sure that it fits into this context. Perhaps it'll be good to find out how the vehicle in question looks like.