What's a Spider Gear

Dec 26, 2005 Last reply: 20 years ago 3 Replies

Hi,



I'm in the market for a used F-250. Yesterday I drove two...a 1999 with 98k miles...and a 2002 with 58k.



Both exhibited the same odd "feel" when starting from a dead stop.



Right as you begin to move...there is a "thunk" somewhere in the drive line. The used car manager at the dealer that had the 2002 said it was "the spider gear" in the rear axle...and was "normal wear"... (DON'T YA LOVE IT WHEN THEY SAY THAT...).



The 98 truck had the same feel...but it was to a greater degree.



Of course...new trucks don't do this...and neither do others that I have ridden in.



What is your diagnosis of this...and what will it lead to as the years and miles pile up? Is there a fix?



Thanks, Chuck



Not really. The problem is likely splines in the driveshaft engaging with the transmission. It could also be u-joints, so I'd have any vehicle I was interested inspected before I laid down any cash.

Spider gears are the side gears in a differential - the little gears that divide the input power between the two wheels. If you will hunt for a picture of a differential on the web, or better yet an explanation of how a differential works, you'll see what I mean.

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