Yanmah 186d 4WD transmission gear problem

DrivenByFear · Aug 31, 2015

Hi there a few months ago I purchased a yanmah 186d 4WD. Good engine starts instant every time.. However when you hold the clutch in and go to change gear with lever It doesn't change that's the problem

So I unbolted the seat and took the top lid off. everything looks fine there. Not such an easy fix. So I unbolted all the pipes , drained the oil from gearbox and unbolted the gearbox to have a look for any damaged gears but there all in good condition. I also took the back wheels off and the brakes were locked and needed freeing up but is ok now, The only thing I can think of is maybe the o ring seals need replacing on the the drive shaft. Also checked all filters and strainers there clean. Any suggestions why it won't change gear ?

winston1 · Aug 31, 2015

Welcome to the forum. :welcome: range gears or power shift gears?

DrivenByFear · Aug 31, 2015

Thanks for the quick response still very new to all of this. What I mean by gear is neutral, first , second gear. Those gears. I believe the machine is stuck in neutral and will not shift into first gear to drive.

normde2001 · Aug 31, 2015

winston1 said:
Welcome to the forum. :welcome: range gears or power shift gears?

You need to be more specific. Are you saying the tractor will NOT move? How about in front wheel drive?

California · Aug 31, 2015

Ok, step by step:

Which transmission are you concerned about? Range, or Powershift?

The range shifter sticking out the right side of the transmission has three ranges. From back to front, they are 1 N 2 3. When you let out the clutch power goes through this transmission direct to the PTO, and also into the second, Powershift, portion of the transmission.

The Powershift portion is controlled by hydraulic fluid that is routed through various passages to engage internal bands and clutches to select R N 1 2 3 , same as an automotive A/T.

If you suspect the range portion, engage the PTO (lever behind your left knee) and look at the PTO shaft sticking out the back of the transmission. After you let the clutch out the pto shaft should turn.

Then make sure the range shifter is in anything but neutral and shift the little Powershift lever. You don't need to have the clutch depressed for this, but the tractor will move so have some space in front of you. What do you see/hear?

The problem could be simply that the Range selector is at the Neutral position. Also, the different selections of the Range selector give different sounds in the Powershift portion depending on which range you chose. Observations?

Aside from the Range shifter not engaged in a gear, debris in the hydraulic fluid blocking a passage (or low fluid) is the most likely problem. I don't recall anyone ever posted here about broken internal parts in these transmissions.

DrivenByFear · Aug 31, 2015

The tractor will not move in front wheel drive or 4wd back or front. That's how I bought it.. I'll see what my brother says tomorrow because he helped me unbolt the gearbox from the machine.

DrivenByFear · Aug 31, 2015

Reading your post having low fluid could be a possible. But When I drained it , still Looked like it had a lot of oil still in it. Didn't look clean though so I won't be using it again. Going to have to get some fresh Oil and fingers crossed that's the problem

California · Sep 1, 2015

I should clarify - I haven't read of stripped gears etc in these but we have seen posts saying the pressure relief valve spring broke, and I think I remember one where the Powershift's internal hydraulic pump needed to be overhauled. Basically stuff where a Automatic Transmission tech would be the person with test gauges and some intuition based on experience. Does anybody else recall anything more relevant?

Its just a wild guess on my part but I wouldn't be surprised if the Powershift shares some internal parts with some Japanese car AT of that era, around 1980, so a tech specializing in those might have the best intuition. But you should be able to test hydraulic pressure at some test points if you can find manuals describing the test process. Note this internal hydraulic pump is like that of an AT, internal to the Powershift, and separate from the tractor's hydraulic pump mounted forward on the engine which draws from the same sump.