I just bought a precombustion chamber tool group on ebay, all tools are correct except the 5F8353 wrench adapter which engages the internal splines of the chamber. The number on the tool matches the one in my service manual, but doesn't fit. I count 56 splines on the tool, and only 48 splines in the chamber. Is it possible this set fits a different model other than D2, but carries the same part number? Has anyone seen this before?

I counted (going cross-eyed:D ) 48 splines in my 5F8353 wrench.
I've seen that advertisement on ebay, better take it up with that Chicago Products Group.

Should've gone right to Cat in the first place, I should know by now that you usually get what you pay for. You're right about going cross eyed, I had to count those splines three times to make sure. Thank you for your help.

This is probably going to smart a little:D
That 5F8353 I have came from www.heavyquip.com They still have them $8.20. You can make do without all that other stuff in the group with a little ingenuity:)

Oh, and yes it fits the chambers just fine.

Is the tool you have the same diameter? On another post we were trying to figure out what wrench fit the later 955 330AT engine pre-coms, where the 5F8353 was to small. Maybe that's it.

I measured the tool, it is larger in diameter than the chamber. As you mentioned, I had already made the tools to remove and install the top retainers, but couldn't figure out an easy way to create a splined tool for the chambers. I've been assured I can return the set, we'll see later today. Thanks again.