1991 Ku1991 Kubota B20 CUT 4X4 with hydrostatic transmission knock

SethJohns

New member

Equipment
1991 B20 4x4 compact tractor with front loader and 3 point
Jun 20, 2019
2
0
0
Fort Klamath, OR
Looking for help with a substantial knock when moving forward, less so in reverse. Just changed all fluids and filters but that didn't make it better.

I'm going to lift the lid on the transmission and have a look. Maybe fish for metal with my magnet.

Just to gather a little more information, does the knock speed up or slow doesn with engine RPM change or ground speed change? Does it do it with the differential lock engaged (if applicable), or more going straight or when turning? Different in high/low range? Wondering if the knock could be in the rear end rather than in the transmission itself. Any sign of metal in the fluid when you changed it? Might cut the filter apart with a tubing cutter to inspect inside it.
Can you feel the knock at all through the hydro control or the chassis, or it just audible? Hollow thunk or metallic tink?

Speeds up with ground speed, same in hi / lo range, same turning / straight, not sure about differential lock (I'll check tomorrow). I feel the hollow clunk on the transmission and chassis, I'll see if the sane is true for rear end tommorow.

No metal in old fluid, already threw the filters out.
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
4,884
1,619
113
Mid, South, USA
Bet you'll find a broken pinion and/or ring gear. Less likely a broken side or spider gear in the differential. Seen lots of each.