SX/M Drive knocking - U joint?

[ssquare14]

Volvo penta 4.3gl - SX M outdrive

At idle there is a loud knocking/clunking from the lower unit. I think it increased with speed when I rev'd in neutral in the driveway, but it was hard to tell. I can hear a similar knocking on the water when pulling a U turn.

I recently changed the lower unit oil and it was fairly clean. I have never removed an outdrive before, but from what I have read it sounds like it could be the U joint...in which case im out $500 if I do it myself. Sound like a U joint?

If so, how is the replacement? Can I do in a day or so (winter is coming)?

 

[dypcdiver]

Easily done in a day, I did gimbal bearing, seal and new spiders in a day. You need to make or buy a tool to push the spider out leaving the input shaft in the drive.
There are several write ups on how to remove the drive on this site if you use the search at the top of the page you should find them.

 

[Sparkinator]

Make sure and get an alignment tool as well. You can get them off Ebay for around 50 bucks and that includes shipping. You need one to ensure your alignment is correct whenever you pull your drive. If you have a problem with your gimbal bearing, then it serves as an installation tool as well.

 

[ssquare14]

Update for future readers.

Although I recently changed the gear oil, the level was low. After topping off with fresh gear oil the knocking stopped. I probably still need to check the gimbal bearing in the spring - while the unit is off, what should I be looking for while inspecting the U joint?

 

[dypcdiver]

"U" joints should be smooth in all directions and with no play. If there has been any water in the bellows or the joints are seriously rusty I'd change out the spiders as they are cheap and easy to do. Gimbal should also be smooth to rotate and no play, again if there has been any water ingress change it.

 

[ssquare14]

Update: I eventually took the boat to a mechanic. There was a small tear in one of the bellows which more than likely allowed water inside the housing causing my gimbal and U joints to fail. The gimbal was in rough shape (basically exploded) and U joints needed to be replaced as well. Also had him replace bellows and seals (obviously). There is still a slight knocking in the rear when trimmed at certain angles, but not nearly as much as before. Cost about $1k - hope it helps future readers.

 

[GA_Boater]

Thanks for the update. :thumb: It doesn't happen enough.