main drive shaft (coupler)

bwilliams · Jan 30, 2011

I have a yanmar 169d. I used it about 100 hrs after buying it. Then the clutch plate cracked. So, I split the tractor and replaced clutch, pressure plate, pilot bushing, and throwout bearing. Maybe a few other things too. When I put it back together I installed the splined coupler sleeve over the main drive shaft connecting it to the rearend.

The tractor has run fine for 20 hours or so. But then I started having trouble shifting. The clutch did not seem to disengage. I have split the tractor again to ensure the throwout bearing, pressure plate and clutch plate are all still in good shape. All looks good.

The only thing that I could find is that there is some end float in the main drive shaft. It can slide in the direction of in/out of pilot bushing. My main shaft is tapered at the pilot bushing end. I'm guessing that if the end float is excessive then the main shaft could slide out enough that it wobbles in the pilot bushing and then the clutch plate could wobble too. Which might keep the clutch plate in contact with the pressure plate even when its supposed to be disengaged.

I noticedd that there is a hole thru the main shaft coupler that seems like it could hold a roll pin. If a roll pin (or cotter pin) were put thru this hole I think it would shim the gap between the main drive shaft and the shaft from the rear end (prevent the end float).

Is there supposed to be a roll pin there? My repair manual and parts manual don't show the coupler, let alone a roll pin. Or, does anyone have any other ideas for why the clutch is not disengaging? BTW, its not a stuck clutch because I keep the pedal blocked when not in use and it will disengage while not running.

thanks, Brian

normde2001 · Jan 30, 2011

Are you sure the clutch is adjusted properly. (1/2" free travel in the pedal)? IT should be a positive movement from the pedal all the way through to the pressure plate, with no wear in between, with any front, back movement of the shaft having no bearing on it, (that's just a place to hang the TO bearing carrier). Is there an inspection plate above or below the clutch in the bell housing?

winston1 · Jan 30, 2011

Don't have a clue if your 169 is like this 1401, if so, if may be suppose to have #8 in the drawing. Yanmar Tractor Parts: TRANSMISSION_INTERNAL_2

Gary Sweat · Jan 30, 2011

This is a photo of the 3PT gears with a spline coupler. There are two couplers on the driving shaft and both only use cotter pins to keep the shafts from traveling in the coupler. I would think you could use a spring pin or a cotter pin.

bwilliams · Jan 30, 2011

Wow this site is really cool! I posted the question at 11pm and have three very useful responses by morning.

The pedal adjustment is okay. Maybe not perfect, but since it works intermittantly then I don't think its the main problem.

The splined coupler in Winston1's post is the coupler that I was talking about. Is part number 8 a cotter pin or spring pin?

Also the latest response with picture of coupler inside the transmission with the cotter pin seems to answer the question of whether a cotter pin work.

Thanks again, Brian