Changing Transmission Oil

[GKuffner]

While this is the end of the season and the manual for my new 3YM20 Yanmar said that I had to change the gear box oil after 50 hrs or at the end of the season. So I used my vacuum pump to suck out the ~300 ml of gear oil which went well. I slowly added new gear oil to the transmission. The silver colored 4" dip stick is difficult to read with new oil. There are two marks on the dip stick, one about a 1/4" above the bottom and a second about a 1/2" from the top. The top mark is actually a hole drilled through the hollow tubular dip stick. After I poured oil into the transmission I waited 10 minutes and took a reading. I found that the new oil level was about a 1/2 over the lower mark on the dip stick, so I used my vacuum oil extractor to remove a little oil until the oil level was just above the lower mark on the transmission. I think that this is where the oil level was prior to my changing it.

My questions are? - How important is it to maintain the level of gear oil in your transmission? My manual doesn't say where the oil level should be on the transmission dip stick - where should it be? What kind of bad things can happen if you over fill it?

Gary

 

[ITMaster]

My 3JH3E

Specification calls for the oil level to be maintained in between the marks. The manual says not to overfill it, so I don't know how bad it is to overfill it. I don't over fill it. Mine calls for 30 ml if I recall, so I measure with a metric clyinder graduated in ml, the required oil quantity and transfer it into the transmission. That way I don't juggle back and forth with under and overfilling.

I check it, but it never indicates that I need more oil, so for my good fortune, it is a non-issue.

You could try a turkey baster if you lack a graduated cylinder.

 

[Rich (P303)]

I do believe that the first mark from the bottom is the fill line... and the bottom of the dip stick is actually the lower mark. When you check the level... do not screw the filler screw down... it should just rest on the top of the filler hole (so my manual says).

I do not know what the hole drilled through is.

That is the way it is... on my 1984/2GM.

 

[Steve Dion]

Too much oil = too much pressure. If you over fill the tranny, you can cause additional pressure that may blow out your tranmission seals. This can be a costly mistake. I am sure that resealing a transmission is not inexpensive.