Will a wide gauge undercarriage of a 1J style 22 and 22 tailseat parts work on a small 20? I came across an old video of a wide gauge tailseat small 20 and I think we have all the parts needed to make something like that. We have a small 20 with a stuck engine and trashed finals, but straight sheet metal. Can I take the finals out of a wide gauge 22 and 22 tailseat parts to make this conglomeration? The sprockets, idlers and tracks look identical, but I’d rather ask before tearing apart 3 tractors. Thanks

I had to dig out my "Bob LaVoie" book to refresh my memory. The small 20 is a relabeled 15, with some good improvements. The book says that the engine, transmission , finals and undercarriage are the same as the 15. Some undercarriage parts from a 22 are the same as a 15, but I dont know which ones. You should pick up a copy of "Caterpillar Gas Tractor, Restoration and Interchange Manual". Some members bad mouth the book and I have seen a few mistakes, but it is a wealth of information. Order a parts book for a 15 and a 22 and compare. I dont know if there is a parts book for the small 20 available? I had a small 20 but could not get the head off of the engine and was offered enough money for it that I gave up and sold it. GOOD LUCK.

Thanks for the info. As with any project like this it will be a while before any wrenches get brought out. But I look forward to reading more about it. 

You might want to start looking for manuals on Ebay. The reproduction manuals have very poor photos. Actual manuals cost more but having a good photo really helps.

I may be wrong but I believe the 8C Twenty and the 22 share the same Fifteen transmission. That is why steering clutches are weak on 22's, it is really 15 clutches. You are on your own on the tail seat modification, I would not have one in my stable.

We should have all the parts needed for the tailseat conversion. And if not, more swap meets and tractor shows should help out as well.