transmission gear compatability?

[winton]

I have a 51 model cub that runs good but no 3rd gear and bearings seem worn bad,fair amount of play in trans and kind of noisy. I can get a 68 cub cheap for parts. can the newer 68 cub gear train fit the 51 model? I would like to use pto from 68 also. thanks

[bob in CT]

Yes. All the same. Even less wear can be found in gear sets Cub Cadet gearboxes, as they were usually used an hour a week in the summer and kept in a garage. Keep your shims in order. Shims follow the castings, not the gears.

[Gary Dotson]

Yes, it should fit just fine.

[John *.?-!.* cub owner]

I am not sure where the change was made, but in the later ones there was a difference I believe in the 2nd gear ratios. You will be ok though so long as you switch the upper and lower gear together, even with the different ratios. If just switching half the set, count the number of teeth, that is where the difference is.

[bob in CT]

You have a couple of options.
You can swap the entire gearbox. the least amount of work and if the other tractor is not running, you can find out if the gearbox is any better than yours.
You can swap the gears to keep the original casting number.

Shifters are probably different, but that is just the top cover.

One thing that is different is the inner bearing for the driveshaft. The old case has a larger roller bearing, the newer case has a small needle bearing. Both bearings roll directing on the driveshaft, which is induction hardened. This bearing takes a beating as it it on the top of the case and requires splash lube. For the early case, there is a fix where you can grind the shaft a little and replace the roller with a sealed bearing. This is an excellent upgrade and saves buying a replacement driveshaft. This is not an option for the later case, as the needle bearing and machined bearing opening is much smaller in diameter. Replacement bearings for the original Torrington bearing do not have the oil hole that allowed splashed oil to drip right into the bearing cage. I have swapped Cub Cadet gear sets into both styles. Because of the bearing, I like the earlier one with the sealed bearing fix. If you are going to use the PTO with a stationary attachment, no lube gets splashed up to the top of the box when it is in neutral with a direct connection to the PTO.