I made notes a lot of what I did and measurements of stuff and have that info in many of the pictures also. I talked to the guy in our club that told me that the JD stuff will fit and I asked on his if he narrowed up the JD differential case to fit it in his and he said no. I didn't think it would ever fit in there but I tried it and it went in. So all I had to do to the stock JD differential was drill and tap 6 holes for the ring gear, 2 of the holes come out in the stock JD holes with just a little filing of the holes so 2 of the bolts have nuts on them. I taped the carrier flange for 5/16" fine thread Allen head bolts, the new holes come out in the thick part of the flange and I figured the fine thread would be stronger than coarse thread. I was worried if the metal would hold threads very well but I torqued the ring gear bolts to 32 ft lbs and they felt very solid probably could go to 35 lbs without a problem. I had lock washers on the Allen bolts at first but when I tightened them up one felt funny and I found that the head of the bolt and spread the lock washer open so I took all the lock washers off and used high strength Loctite on the bolts. I used all metal locking nuts on the 2 bolts with a nut. With the stock JD differential the left side bearing cup is very narrow plus it had to make a 1/4" aluminum spacer for between the left side cup and the housing. The race is inside the hole in the case so I figure the case will help support that bearing and being on the other end from the ring gear there probably isn't the stress on it like the ring gear side. The ring gear side cup is pretty short also but the same deal, the race is inside the hole in the housing to help support it.
Towards the bottom of this web page are pictures and details of the parts.
Also with the bearing cups so short I drilled a couple 1/4" holes in them that come out right behind the race so I can put a punch in the holes to be able to drive out the races if I ever needed to.
A good machinist probably could make some bearing cups that would be stronger than the modified stock ones I used and wouldn't need a spacer on the left side, but when the rear end broke last year the cast cups held up just fine so I am not worried.
The ring gear will need to be fastened to the differential after it is in the case.
I noticed the JD axles are worn some where the needle bearings run on them after one season I assume because they are way to soft for a bearing so maybe a bushing might work better. The guy in our club who also runs the JD setup has some kind of aluminum deal bolted to the end of the Cub axle housings and still runs the splined JD wheel hubs on his so I assume he has some kind of ball bearing in there. He offered to make me a set of shafts from some good chrome molly steel,
He says making the coarse spline is easy and I can just weld some Cub wheel flanges on the ends like I did on the JD axles. I think with the grabby aluminum clutch disk out of it and I modified the clutch linkage so the pedal pushes much easier so I can slip it off the line this year I don't think I will ever twist a JD axle again with my small engine but maybe the chrome molly axles would hold up much better where the needle bearings run. Or maybe its possible to case harden the JD axles in that area, I don't know much about that stuff.
So in the end this JD setup probably isn't the best deal the way I did it but if someone is able to make some real good axles and bearing cups I bet it would be really strong. I was told that some of the Dana 30 front axles in the old Jeeps and other makes have fine spline axles so maybe that would be a better way to go but I bet that stuff would be hard to find.
But for a low buck setup and the stuff on Ebay cheap and for a tractor that don't have a ton of HP I think the JD setup is a fairly easy way to go now that I have figured it out better the second time around. The guy in our club with the JD setup in his runs a very strong open super stock and he said he was breaking the Cub ring gear all the time with the Dart setup so he went to the Dana 30 stuff because the flange on the differential is stronger, he said he only lost one ring gear after switching. But to be fair he is a machinist as his job and goes all over the world for his work so he can build stuff I can only dream about. I think he even built his own over head valve head on his engine in the tractor and his own splined 8" diameter clutch deal because he said the 7" stuff would slip on a good power track. I would love to get a look at how he has the rear end built in his Cub but I don't think that will ever happen.
He will answer questions about the JD setup he did but that's all, he won't give me any more info other than what I asked about and I don't want to be to big a pest with all kinds of questions.
For example I have no idea on how he mounts the ring gear to the Dana 30 carrier, For all I know he is able to put bigger holes or more holes in that hard Cub ring gear to bolt it on stronger. Sorry for writing a book here, but I hope there is enough info here that you can maybe put something together for your website. I have gotten a few emails about the JD set up but I felt bad because till now I didn't have any real good info or pictures on how I did it, and the way I first did it I did many things wrong or machined things I didn't need to. Like I said before I don't know if I still have all the answers on how to do this, but if I got it to fit with the small lathe I had to work with and not much experience as a machinist than about anyone should be able to do it who can make stuff.