931 with D4 tracks??

Hello all: Thank you for such a great resource as this forum regarding these old classics.

Several years ago I purchased the subject loader, whose label plate indicates the 81U serial number. Most of the time all the parts match up to that number no problems. The tracks, however, appear to be a different story. I had to repair a track adjuster a few years ago, and the replacement track pin from the local Cat dealer didn't match up (I had to burn the old one out to split the track). The pin that the Cat dealer sold me was just too small (length and diameter). I started calling around, and finally caught up with a gentleman that told me a limited number of these machines came with a D4 undercarriage instead of a D3 (he also noted that the cat dealer would likely think I was crazy if I mentioned it, and they did). To the point, though, I now have to do the other track adjuster, and I've since lost the part number that the man gave me, and his phone has been disconnected. Can anyone here point me in the right direction? I tried to get the cat dealer to look up the part by dimensions, but apparently that's not possible in the new point-and-click era. Measuring best I can before I split the track, it appears the pin is around 1-1/4" diameter x 7" long. The part numbers on the links are unreadable. Is there a parts book or some other reference material available for purchase that supports machines which are so configured? I need to keep this machine running to finish up a few projects before I can bring the old girl into the barn for a teardown and restore!

Any help is appreciated.

Clean the side of the link off good and you will see a part #. The dealer can cross reference the number to a track chain with your parts.
Later Bob

I have a chart that shows the early D3/931's used 6.75" pitch chains (D4) although it is not mentioned in my undercarriage parts book.

For either 2.00" or 2.12" OD bushings the master pin used is a 4K3919.

There is also a 8L5560 master pin used on early 6.125" pitch chain.
I suspect this is the pin you are given that is to small.

Later D3/931's are all 6.125" pitch with alligator link masters.

You could consider converting it to alligators but last time I priced this it was a very expensive exercise!

Thanks guys, looks like the 4K3919 is going to be the one. I was able to get a guy at the Cat dealership to measure the pin and it's consistent with the size of the ones that are installed. Should be in the mail and arriving next week, despite his protests that "this pin will never fit a 931".