John Deere 40U - Transmission input bearing failure

[Glen D Anderson]

Good day!

So, as the title suggests the front bearing on the transmission input shaft on our 40U failed. This occurred while the tractor was stationary & being ran at a variety RPMs for testing some other repairs I had done to the unit(engine & T.O.M. O/Hs)

While I was testing the T.O.M. I could hear a slight squealing / grinding noise coming from the front of the transmission. The noise got progressively louder so I shut the engine down. I removed the shifter cover from the transmission & inspection revealed the input shaft front bearing was bone dry & failing as a consequence. Further investigation revealed the port at the front end of the lube trough was plugged with a piece of a broken shift fork & sludge.

Full disclosure: Rewind the clock a bit. While the tractor was apart for the engine & T.O.M. repairs I had removed the transmission shift cover to replace the gasket as it had been torn from an impromptu overshifting repair years ago & we'd been getting water in the trans. ever since. While the cover was off I noticed there was quite a bit of sludge in the bottom of the transmission & in the lube trough so I washed everything off with the solvent sprayer thinking I was doing it a favor. LOL Well, I guess I didn't pay enough attention to the port at the end of the lube trough as I clearly pushed the piece of broken shift fork into the hole along with some sludge. That combined with the fact that the solvent washed most of the lube out of the bearing lead to the failure while I was testing the other repairs.

I thoroughly cleaned out all of the lube ports in the transmission case & bearing quill & reassembled with a new bearing cup, cone, & seal. Being a little gun shy I wanted to make sure that lube was flowing to the bearings properly before I reconnected the front half of the tractor to the back so I spun the transmission with a heavy duty corded 1/2" drill that is allegedly rated at 700 RPM. I found that the trough fills up immediately(within 10 seconds-ish). [i:1c33b0cacc] Now for the confusing part[/i:1c33b0cacc]............Despite the trough being full(running over) and seeing oil running out of the output shaft front bearing, I see nothing but a little bit of oil glistening in the rollers & cage of the input shaft bearing - no oil running out like I was expecting?

So, is that normal? Was the drill not spinning it fast enough to replicate an idle situation? Does oil get flung up onto that bearing from the 3rd gear once you start driving? Am I simply over thinking things & should just put the shift cover back on & forget about it? I have to remember the transmission run fine for the first 70 years. LOL

Some pictures for reference:

This post was edited by Glen D Anderson on 02/23/2023 at 11:16 am.

 

[Glen D Anderson]

Forgot to mention that I couldn't find any description of how this lube system works in the JD service manual at all. Thought they'd at least mention the lube trough and the need to keep the galleys clean during repair procedures but not a word......

 

[M-MAN]

Old Murphy strikes again! I
wouldn't have thought about that
happening at all. Might be the new
bearing and race tolerance is close
enough to not allow a lot of flow.
As long as it's got an oil film
that's really all it needs. I think
you'll be good to go.

 

[Glen D Anderson]

The SM calls for .002" - .004" end play and this one was sitting just under .005" with the new bearings. The smallest shim in the current pack was .005" and I didn't want to have to try and build a. 002" shim so I left it as is.

Regardless, I would think there is still plenty of room for the oil to run out between the rollers even if there was preload on the bearing?

It's hard to explain it without being able to point to the transmission case & bearing quill in person but the position of the oil ports / galleys in case in respect to the port in the bearing quill leads me to believe that very little oil could actually flow out of that bearing. Not because of the port / gallery size but due to a lack of difference in elevation if that makes any sense? LOL

I forgot to take any pictures of mine but here's some pictures of the bearing quill I found on the 'net. The port in the quill that feeds the bearing is located
at the bottom when it is installed in the transmission. When you look at the postion of the ports in the case and imagine where the lower edge of the bearing cup would sit it seems that the oil would barely be able to flow over the edge and out through the bearing cone.....

Also the bolt holes in the bearing quill are offset so it can only be installed in one position.

It's a head scratcher for me for sure and I guess it's going end up being one of those "I don't know how it works but it just does!" LOL

 

[used red MN]

Sorry you had to experience such an unusual failure. I
always say.. no machine machine made by man is
perfect, so any inconceivable thing can and will fail.
Help someone out who is not in the know, what is
T.O.M.? All I find is ..Task Order Management.. which
does not really seem to apply.

 

[jCarroll]

TOM is Deere's 3 point hitch - Touch-O-Matic.

 

[Glen D Anderson]

It's frustrating at the time but I find problems like this tend to improve one's overall situation. You're forced to learn more about the machine than if it were just a cookie cutter repair with no anomalies. Same with lessons learned the hard way because of a mistake of which I've made a few. LOL You damn well don't forget those. LOL

(quoted from post at 23:17:27 02/24/23) Sorry you had to experience such an unusual failure. I
always say.. no machine machine made by man is
perfect, so any inconceivable thing can and will fail.
Help someone out who is not in the know, what is
T.O.M.? All I find is ..Task Order Management.. which
does not really seem to apply.

 

[deeretails]

I just rebuilt an MT transmission and the oil trough was completely blocked. Oil is feed to the input shaft bearing via this arrangement, the front pinion shaft also is lubed this way.
Check close and you'll see a drilled passage between the two bearings. If you pull the cover off the pinion shaft bearing make sure no rust has accumulated there, an indication of no
oil.

 

[Glen D Anderson]

Thanks.

The picture I posted in this thread above shows the 2 galleys you mention.

I did remove the cover from the output shaft which was a good thing as the washer behind the nut was "dished out" & there was no preload on the bearings.

I don't suppose you looked in your transmission after the rebuild after it had ran for a bit to see how much oil was actually coming out of the input bearing?

(quoted from post at 05:40:33 03/02/23) I just rebuilt an MT transmission and the oil trough was completely blocked. Oil is feed to the input shaft bearing via this arrangement, the front pinion shaft also is lubed this way.
Check close and you'll see a drilled passage between the two bearings. If you pull the cover off the pinion shaft bearing make sure no rust has accumulated there, an indication of no
oil.