MTD Deck Vibration

[lefty]

Just to be safe, I'm going to replace everything. None of the components are really bad but none are really good either, including spindles. I think the vibration may be the result of harmonics. Maybe it wasn't very noticeable with an old stretched-out belt because it would just slip but maybe during a certain point a few pulleys will be dragging at the same time and the new belt is grabbing a lot better.

The vibration is rather subtle and rhythmic. Sounds like when you hear a machine running in the distance for a long time and start to hear a rhythm to it and you tilt your head because you're not sure if you're actually hearing it or imagining it. When you're on the machine, you can feel it, and like I said in a prior post if you watch the top side of the deck the idler pulley (not the pivot one but the one that swings when you engage) will bounce up and down during the period of vibration. It's tight on its mount so it takes the arm with it. It's not constant though...it's rhythmic.

The deck is in wonderful shape and was able to get some of the components in "used-like new" condition. I guess that means the packaging is damaged but part is new. So they were like 1/2 price. I went with 2 new idler pulleys and 2 new spindles. I've already got new blades and a belt. Hopefully, this does the job.

Edit: And I wouldn't be surprised if the spindles are bent slightly. Not enough maybe for me to notice visually but I have heard the old blades hit the curb.

[Arkie]

Those types of vibs are not easily found.

I had one similar once that I will not forget. Turned out to be a roller bearing, the type bearing that has the round roller bearings and only one of the rollers was bad. (small flat spot) It would eventually get on the bad side of the ONE bearing every once in awhile in the race which would cause intermittent vibration. All the other rollers bearings inside the race was ok. One bad apple ruined the whole barrel. Even after it was found to be bad it would not feel rough very often when being checked manually in the hand. Was ok more often than bad.
I eventually removed the bearing's side seal after I knew the bearing was bad just to inspect and could keep turning the bearing slow and eventually seen the one bad roller bearing

[lefty]

Well I've replaced just about everything and still have the vibration. The only thing I hadn't replaced was #37, the shoulder spacer which KE4 suggested. So I've ordered that. If that doesn't do it, I'm giving up.

Funny, when I ordered new spindles, I experienced a lot of the same problems mentioned already in this thread. Both showed up with bent pullies. They must have been dropped or something. Wobbling all over the place. I went ahead and installed the old pullies and complained to Amazon so they refunded my money. I guess that worked out pretty well for me since the spindles themselves are fine.

The new ones came with a spacer while the original has the spacer built right on the pulley. The separate spacer raises the new pulley up just a bit higher, which is why I think I needed the washer to keep the nut from bottoming out before securing the pulley. Everything aligns well.

The original pullies I put on the new spindles looked in really good shape to my eye. Running true and not a log of wear on them. What are the chances that this decision is going to bite me in the behind?

[bgsengine]

Other thing that will allow for harmonic vibrations like that is the deck linkage itself - the mounting holes for the pins wear into an oval shape so as the belt moves around pulleys , (belt dimensions are never perfect all along its length) it pulls and relaxes on the whole deck assembly - with the pin holes out of round, deck will shift forward and back and at certain points, everything is "in tune" where it seemingly runs smoothly, then the harmonics hit and you get the vibration. Almost nothing you can do to solve that without completely replacing all the mounting points, suspension and linkages, hardware, etc - by the time you do that, you spent enough to buy two new tractors.

[Arkie]

Other thing that will allow for harmonic vibrations like that is the deck linkage itself - the mounting holes for the pins wear into an oval shape so as the belt moves around pulleys , (belt dimensions are never perfect all along its length) it pulls and relaxes on the whole deck assembly - with the pin holes out of round, deck will shift forward and back and at certain points, everything is "in tune" where it seemingly runs smoothly, then the harmonics hit and you get the vibration. Almost nothing you can do to solve that without completely replacing all the mounting points, suspension and linkages, hardware, etc - by the time you do that, you spent enough to buy two new tractors.

This is a very good explanation by bgsengine of such.as a possible cause of a mower deck vibs and rattling deck noise)
I have a 52 inch deck on a mower and almost all the linkage holes are oval shaped, has new bearings, belts, pulleys. Deck is completely rebuilt except for the wallowed out linkage holes.

I can adjust the deck or the anti-scalp wheels so as the anti-scalp deck wheels touch the ground little more than they should (instead of the mower carrying the weight of the deck with the deck wheels slightly off the ground at it's lowest position as it should) and the deck oscillating noise almost quits.
One of these days I plan on just drilling some holes in some metal plates so as to make washers and just tack weld the washers over the elongated wallowed out linkage holes.

[KE4AVB]

Also don't forget to check the double stack engine pulley too for bent places.

[lefty]

I was finally able to get my hands on the spacer for the deck brake arm assembly after some shipping errors. I installed it and the fibration still persists although not as bad. There is still play so maybe some of the meat on the brake arm has worn off. That's the only thing I haven't replaced...that and the springs, and idler pulley bolts. The hole doesn't look ovalled out but maybe the thickness of the arm?

I don't think I'm supposed to be able to wiggle that arm around...up and down. Perpendicular to the directions it's designed to operate. Or is there supposed to be play there?

At this point, all that's left are some idler pulley bolts and springs. I'm starting to wonder if the brake arm return spring may be weak and causing this.