Back when my 755 was just out of warranty (maybe a year and a half old) the steering valve failed and was blowing hydraulic fluid out the steering shaft. I removed and replaced it with a new one. That was about 16 years ago, so my memory is kinda hazy. I remember spending about 3 hours dissassembling, and about the same reassembling. I also recall the muffler coming out. I did the job without benefit of a service manual, and the machine has been almost troublefree since.