Lets grow the sport
I won’t go into much detail about building the gearbox but will direct you to buy the “how to video” from MWSC its the best 30 bucks you will ever spend. This will give you detailed info on how to setup the gears and carrier.
So basically the only part you will keep from the Cub diff will be the housing. The stock carriers and gears will not hold up.
The most common carrier being used is the Dodge Dart setup.
They seem to hold up well and you can buy them with axles for around 350.
I would buy the MWSC carrier bearings and holders as well. I prefer the ring and pinion gears from True Gear (Also known as Canadian gears) they are reverse cut and don’t spread with under load these are around 450 for set.(Also sold by Vogel)
I also like the fact that Truegear top shaft or pinion is a left thread so it does not loosen under load.
As far as gearing I would say if your running a 1105 with turbo start with a 38% overdrive with 24/25/26 gears. I like to keep my reverse but if you want 4 speed maybe go with 23/24/25/26 you can use that 23 for those really sticky tracks that come up once in a while. MWSC and Vogel sells kits that include spacers and shift forks and gears.
So another way of building a diff is using planetary gears. This is by far the best setup to have.
What is nice with this setup is you can actually use a stock cub two peace carrier. The load is shared by more gears and removes stress off the transmission and carrier.
Planetary gears have been used for years in bulldozers and other heavy equipment for this reason.
They are pricey but if you take into consideration the cost of dart carrier and heavy ring and pinion and snubber kit and so on… it comes pretty close to the same.
Zack Kerber sells them for 1650 and of course there work is always top notch. I believe there is a wait time to have them built.
It is possible to get it to slip in with bearings in place but takes some doing. A little trick is to sand the carrier some where the bearings slide on. Make it so they snugly slip on instead of needing to be pressed on. This way if you need to remove them from inside the housing it will be a simple job that will not ruin you bearing cages. Follow the bearing load setup up from MWSC video you bought.
There always seems to be a debate about flipping the carrier on these diesel builds. Most of us who have built tractors have put the flywheel to the rear for various reasons.Weight distribution is the main one. With a big operator it is usually best to keep the weight towards the rear for crappy tracks with no bite. For those of us running a Pro or Limited Pro diesel, a reverse ring & pinion is probably the best choice. But for those running smaller cube engines and non turbos at the local level a stock R&P with the carrier flipped should work fine provided some other modifications are made.
One is called the steel front pinion bearing cup;
It works with the stock bearing.
The other they call combo pack #1 and it consists of a deeper cup and a heavier double row front pinion bearing;
Depending on your HP level one of these should solve the problem as long as the operator uses their head running the tractor. Now you will probably still need to do some of the other mods that are commonly done to the transaxle for pulling applications. A dart carrier or at least a factory two piece with fine spline axles will most likely be needed along with a hardened top shaft. A ring gear snubber isn’t a bad idea either.
For most builds the flywheel to the rear will make for a better all around pulling tractor. It is fairly simple to have the flywheel drilled and tapped for clutch driver pins and eliminate the need for a separate driver. This lets you have the water pump and radiator hose outlets and the radiator at the front with simple plumbing. This is also how big tractors are built.