Slim other post I think answer in that post take back apart check weld on dog.

Is the trans dog sliding all the way out against the retaining ring on the output shaft? If yours is the PTO model it should have plenty of grease packed in there w/ the dogs.

Mike

I have a horse model and it seems the dogs are worn short, has anyone else experienced this problem? The transmission dog turns with the engine and the tine dog turns with the tines but when bolted together the tines will not turn, help. Only thing I know to do is install new dogs, is there a way to check the dogs for wear or something else I could try?

Did you check what we suggested?
Mike

I have checked all of the above, welds are solid, dog all the way out and plenty of grease.

If they're worn there should be evidence of wear on the faces where they engage ie: the corners will be rounded instead of square.
Mike