Cog variants on Thiokol Trackmasters and replacements(?)

So, here are a few snapshots of the drive-gear from several Thiokols TM's of varying years.

Anyone have any ideas on the design differences? Diameter would be pretty clear but it seems as if there are variations outside of just diameter such as the 'pointy' factor and depth of cut, etc... it appears as if it's more than a 'wear-related' issue but rather there were clear design drivers. Some are clearly curving inward while others are pointy with edges curving outward.

Also, how have most people replaced the rubber on these? Is the only option to find replacement parts as either 'new-old' stock or from other old machines? Does anyone have a catalog of design-variations of these puppies? Kind of interesting.

I think you have couple different machines here. The first picture (big yellow) is on a 4T10 or 4T2 like you have. Same with the next one. The yellow covered one below it is a 601 - notice the drop center grousers instead of tire guides. Big far right picture looks like an early 4VL using the 3/4 ton truck free floating axles. Did that machine have wooden grousers? If yours are shot you might give Ockners in Denver a call. How about posting pictures of the whole machine. I'd like to see a bunch of your 4T2, looks like a nice one.

Thanks for the info. Very nice identification. We should have some sort of 'name that cat' contest...maybe at Big Al's blowout.

Well, I started by buying the 4T2 and got a pretty good deal on it after the previous owner did a bunch of work on it. They broke an axle and then replaced it with 1/2 ton...twice... and broke those (go figure since it sounds like it should have been 3/4 ton). So then they replaced it with 3/4 or 1-ton and they didn't have a problem. They pulled a 2,800 lb drag behind it. Front has a beat-up plow on it that I'd like to replace. This one has floating axles too and is a 1961. I haven't seen many of these around but there was an old b/w photo at Thiokol that had these lined up ready for distribution. I'm attaching some pics.

The one on the far right is also the type with the floating axles like you said but it's tags say it is a 1962 4T10 but not sure. I'm in the process of buying it although I haven't seen the tracks. I have another set of tracks if I can change from wooden to metal by also changing the back sprocket. It should be fun to finish off the work that's necessary...mainly external and interior as it sounds like it runs well. What is known about the floating axles? Nightmare? Avoid like the plague? Had to have had some issues given the subsequent OC's. Thoughts?


I'm also making the investment in a flatbed trailer. Pricey little things.