Rc72-38 MMM blades hitting/slipping

Grodrianst

New member

Equipment
L3430 with FEL and belly mower
Nov 22, 2018
16
1
3
St. Louis area
Just changed blades on my Rc72, used new bolts and cup washers, tightened to specified torque. Thought I had lined them up to not make contact. When I started it up the right blade, by the chute, and the middle blade ends hit each other. I loosened the right blade adjusted the timing so the ends of all three would never be in the same space at the same time during a rotation and retightened to torque. When I tested it worked fine for about 10 seconds and then started hitting again, none of the blades seem to be in the timing position that I set. I bought the L3430 and mower about 3 years ago and have no idea how old the belt is so my next thought is that maybe the belt is slipping and needs replaced? Thoughts and recommendations would be appreciated.
 

chim

Well-known member

Equipment
L4240HSTC with FEL, Ford 1210
Jan 19, 2013
1,089
177
63
Near Lancaster, PA, USA
Just changed blades on my Rc72, used new bolts and cup washers, tightened to specified torque. Thought I had lined them up to not make contact. When I started it up the right blade, by the chute, and the middle blade ends hit each other. I loosened the right blade adjusted the timing so the ends of all three would never be in the same space at the same time during a rotation and retightened to torque. When I tested it worked fine for about 10 seconds and then started hitting again, none of the blades seem to be in the timing position that I set. I bought the L3430 and mower about 3 years ago and have no idea how old the belt is so my next thought is that maybe the belt is slipping and needs replaced? Thoughts and recommendations would be appreciated.
Unless you have a chain in lieu of a belt going to the pulleys, they won't stay timed for very long. Sounds like your replacement blades are too long.
 

je1279

Well-known member
Lifetime Member

Equipment
LX2610 w/ 60" MMM, LP 72" FB, Wicked Tooth Bar & 55" Grapple and Woods 60" BB
Dec 6, 2020
528
276
63
Upstate NY
@chim makes a good point. While the blades are designed to overlap each other a bit to prevent leaving strips of uncut grass, that is done by positioning the center spindle slightly forward of the other two. Are you sure that the blades you received are correct for that deck?
 

Grodrianst

New member

Equipment
L3430 with FEL and belly mower
Nov 22, 2018
16
1
3
St. Louis area
@chim makes a good point. While the blades are designed to overlap each other a bit to prevent leaving strips of uncut grass, that is done by positioning the center spindle slightly forward of the other two. Are you sure that the blades you received are correct for that deck?
Makes sense, a belt is always going to have the potential to slip. I got part #70000-25002 from Messicks which their parts diagram says replaces part #76553-34330 for the Rc72-38 deck. I can only see paint scuffing on just the ends of the two blades so I would assume that only the ends are hitting. Any other thoughts? I guess I could measure them but I don't know what they should measure and the old blades were so worn im afraid they wouldn't be accurate.
 

je1279

Well-known member
Lifetime Member

Equipment
LX2610 w/ 60" MMM, LP 72" FB, Wicked Tooth Bar & 55" Grapple and Woods 60" BB
Dec 6, 2020
528
276
63
Upstate NY
Could the spindle bearings be worn out causing enough play for the blades to come in contact on occasion?
 

Grodrianst

New member

Equipment
L3430 with FEL and belly mower
Nov 22, 2018
16
1
3
St. Louis area
Just to satisfy curiosity, I measured the old blades and both outer new blades, can't reach the middle without dropping the deck again, and they measured the same at 24.5".
 

Grodrianst

New member

Equipment
L3430 with FEL and belly mower
Nov 22, 2018
16
1
3
St. Louis area
Could the spindle bearings be worn out causing enough play for the blades to come in contact on occasion?
I don't know about the spindles being worn, does make sense as a possibility. I do know that the dealer did some work on the gear box before we bought it. I don't remember if they rebuilt it or just fixed a leak. If so, I'm guessing that over time as the play increased on the spindle(s) the blades would have worn away where they were making contact and now the square new blades are striking each other.
 

je1279

Well-known member
Lifetime Member

Equipment
LX2610 w/ 60" MMM, LP 72" FB, Wicked Tooth Bar & 55" Grapple and Woods 60" BB
Dec 6, 2020
528
276
63
Upstate NY
I would try removing the belt and checking the spindle bearings for play.
 

Grodrianst

New member

Equipment
L3430 with FEL and belly mower
Nov 22, 2018
16
1
3
St. Louis area
I would try removing the belt and checking the spindle bearings for play.
Thanks all. When measuring the blades I did notice unusual wear patterns on the end of two of them but the third was still flat. I think the worn spindle on the right blade seems to make the most sense. I've got a limited amount of time, so going to see if the local dealer has the parts I need tomorrow to do a rebuild. Will post the results when done.
 
  • Like
Reactions: 1 user

je1279

Well-known member
Lifetime Member

Equipment
LX2610 w/ 60" MMM, LP 72" FB, Wicked Tooth Bar & 55" Grapple and Woods 60" BB
Dec 6, 2020
528
276
63
Upstate NY
You may want to replace all of them while your at it but that's your call.
 

skeets

Well-known member

Equipment
BX 2360 /B2601
Oct 2, 2009
11,587
494
113
SW Pa
For my 2 cents je 1279 makes a valid point, if one has reached the point of needing replaced how far are the others from needing replaced. Granted it is not a cheap proposition, but why take the chance?