Mowing 72d belt wear

[Plater]

I've had this 72d for three years and put on roughly 150 hours. It is used with 3520. For the past couple cuttings, I've noticed a heavy black dust on the deck. After the last mowing I felt the belt, hot but not too hot to touch or hold on to. The front bearing assembly (owners manual calls drive shaft to deck bearing assembly) was so hot burned finger. The same goes for the gear box.

The two bolts that hold the bearing and keep it level were very loose. I've tightened the two bolts as good as possible. They do not have a hex head on bolt head and the hole is not square to hold the bolt for tightening. Another topic I guess. The bottom plate on the bearing assembly was chattering quite a bit on steel plate it sits on. Seems like something is loose or bent to cause vibration?

Further investigation of all bearings proved to not be an issue. All turn easy and no noise. The gear box also seems good. Oil smelled a little burned. Gears sound good when turning gearbox. Actual bearing on bearing assembly is good also. I did notice that when turning the gear box using shaft the left pulley has 1/4" out of round condition. The belt actually moves 1/4" when turning as well.

At this time I have drained the gear oil out of the gear box to change. Considered getting new belt. Do not know if tightening the two bolts will help?

If anyone has any comments it would be greatly appreciated.

 

[beenthere]

I understand this 72d to be a belly mower deck, but not everyone will necessarily get that connection as it isn't in the title.

You may be mowing grass that has mildew spores on it and getting a spread of them on the deck from the cloud that they can produce. Just sayin, as it has happened to me usually about this time during the summer.

Some pics of the black dust would help diagnose too.

 

[Oldtink]

The two bolts that hold the bearing and keep it level were very loose. I've tightened the two bolts as good as possible. They do not have a hex head on bolt head and the hole is not square to hold the bolt for tightening. Another topic I guess. The bottom plate on the bearing assembly was chattering quite a bit on steel plate it sits on. Seems like something is loose or bent to cause vibration?

I did notice that when turning the gear box using shaft the left pulley has 1/4" out of round condition. The belt actually moves 1/4" when turning as well.

I'm with beenthere about the dust assuming it's all over the deck but the two carriage bolts you speak of being loose are of great concern and probable cause for the carrier bearing to be hot.
I've had the same experience on my 3520 and auto connect 72" deck.
At this point you'll either have to buy a new bracket or weld up those rounded out holes (they used to be square to hole the carriage bolts) and buy new carriage bolts. They are a royal PITA to tighten but it will fix a lot of your problems with the carrier bearing getting hot.
The JD installation booklet is a little fuzzy about tightening those bolts. They say to snug them up initially but never mention tightening them for final assembly. You want them tight!

 

[Plater]

Oldtink,

How hot does your bearing get? So far I have replaced everything from the universal joint going forward to the gear box and still hot after 15 minutes of mowing. Everything is tight. I may be chasing a ghost?

After working with the deere dealer, they are trying to find what the temperature of this bearing should be. If you have the equipment (contact or non contact pyrometer) and would be willing to check the bearing race temp and the gear box temp, after mowing, would be greatly appreciated.

Thanks for the previous response.

 

[Oldtink]

I can check that with an infrared probe the next time I mow. Not real sure how accurate those things are but will try it next time I mow.
You are wise to contact your JD service department. They are there to help you and address your concerns.
Replacing all that stuff should have really quieted things down. Keep an eye on those carriage bolts.

 

[nch209]

I'm experiencing the same heat and now some more noise. What cairage bolts are you guys finding loose? On the deck or on the pto shaft that come out of the tractor?

I haven't had much of a chance to hunt my problem- but your descriptions sound like what I'm going through on my 72d/3520.

Thanks!

 

[beenthere]

Can't tell what is in Oldtink's pic that was posted. Maybe the carriage bolts..

 

[Oldtink]

Beenthere, you're good. That was a horrible picture along with no explanation.
I wanted to show the gap between the deck and the assembly that supports the carrier bearing.
When the little carriage bolts get loose that assembly hits the gearbox mounting frame on the deck and makes one heck of a racket as the mid PTO rotates. Here is a much better picture pointing out the bolt location and the resulting wear that occurred from them being loose.
I still haven't checked the temperature of anything but that gearbox DOES get pretty darn hot after 3 hours of mowing.

 

[Plater]

Great explanation.

The temperature of my bearing is better then it was but still hot. I noticed the belt gets hot as well. My major concern is with the gear box failure due to over temp of oil and loss of lubricity. I plan on checking the bearing over time while mowing. Maybe every 30 minutes. Will check bearings for blades, idler bearings, belt temp, and finally the drive shaft bearing and gear box. Will post when done.

I have noticed that my drive shaft bearings begins to howl more when it gets hot. When cool the deck is very quite.

When my bolts came loose it sounded like it chatters. Actually the metal plates are chattering together. Had my wife sit on the tractor with pto engaged watched the thing bounce like crazy. It will be obvious if it is loose. When tightened it does not move.

 

[nch209]

Thanks a bunch fellas! Sure as snot mine was loosey loose! :-(

Gave it a quick snug, but wondering if I can/ should do more? Loctite? It's not like you can draw they down super tight since it needs to pivot. Seems like there should be a better design for such a well thought out overall setup.

Thanks- need to spend some time and look it over more!