swap the hydrogear 347 on Kubota Z400 failed

[Matty_]

I’m trying to fix Dad's old Kubota Z400. The transmission is identical (Hydrogear 347-3000 subbing for the original 312-3000), but we can't get the two halves of the transmission case to seal up.
It feels like something is blocking the differential from dropping into place. We checked the planetaries, they aren't the issue. What else inside those Hydrogear transmissions likes to jump out of place and keep the case from closing?

Also, are the two models truly identical, or are the splines on the input shaft slightly different lengths, meaning it can't quite drop into the pump housing?

 

[Alan]

Be sure to check the thrust washers and bearing races, as they can often shift during disassembly and may stop everything from seating correctly. Don’t forget to also look at the alignment of the swash plate and charge pump gear. The 347-3000 and 312-3000 are pretty similar, but the input shaft spline length and pump depth can vary a bit, so make sure to measure both to ensure a proper fit.

 

[h1ck0ry.b]

I’m trying to fix Dad's old Kubota Z400. The transmission is identical (Hydrogear 347-3000 subbing for the original 312-3000), but we can't get the two halves of the transmission case to seal up.
It feels like something is blocking the differential from dropping into place. We checked the planetaries, they aren't the issue. What else inside those Hydrogear transmissions likes to jump out of place and keep the case from closing?

Also, are the two models truly identical, or are the splines on the input shaft slightly different lengths, meaning it can't quite drop into the pump housing?

The 347-3000 is the correct, functionally identical replacement for the 312-3000, including the input shaft splines. It might be an issue with the charge pump assembly. It's one of the most common reasons why the case halves won't seal on a 3000 series! Check that the seals, check balls, or the small rubber damping pucks on the input shaft haven't shifted or popped out of place. Also make sure the brake pucks oor actuator assembly, if your model has it, are seated cleanly against the differential flange.