JD4300 -- Catastrophic Failure of the Shift Shaft

[reasley]

MJN are my initials and CAD comes from my former life as a CADD Dweeb for 24-years in the engineering world. Engineering and Marketing...sounds like something out of Dilbert.

I'll have to see if that Fortune article is online. The only paper magazine I subscribe to anymore is Fine Homebuilding.

Matt

Good morning, Matt --

I just looked up the article on Fortune's site -- no luck -- and then google, where I found the proper Fortune table of contents:

FORTUNE Magazine: Table of Contents - CNNMoney

. . . but the article isn't hyperlinked.

Sorry about that -- I figured that it would be on-line for sure . . .

Richard Easley

 

[reasley]

Richard,

Can your machinist cut a circular recess in the bell crank (YZ80993) where it contacts the housing? I'm thinking a quad ring that resides in the bell crank and protrudes slightly so that it is in constant contact with the housing. Keeps the oil in and the moisture and dirt out. Since this is a common sump tractor, keeping foreign matter out is quite important.

At one time, Deere offered a rental yard upgrade kit that locked out the C range. I suspect that the purpose was to limit travel speed. On my tractor, the shift between A and B is usually quite easy, It appears that the cogs on the shift collars are always aligned between the low and mid ranges. Shifting between B and C almost always involves a touch to a hydro pedal to bring the collars into alignment and is probably where the most potential for failure occurs. I'm not sure that I'd want the tractor locked in B. If it is doing a job in the B range that really should be done in the A range, there is potential to overload the hydrostatic transmission and build heat. Locking out C, which could be done top side, at the lever mount, would probably be a better choice.

Thanks for taking the time to document the repair. Hopefully, this thread will make all of us more alert for any changes in the way that the range shift operates and any failures can be avoided with a little bit of lubrication.

Good morning, Jim --

The recess in the bell crank is exactly what I'm going to have him do that's what I meant the other day by chamfering and then putting an O-ring in that groove to contact the case sideways. However, I am unfamiliar with the term"quad ring." Can you tell me more about them?

Interesting what you say about the A-B shift being easier this is in keeping with the TSB on hard shifting it states going from C to B or A will be enhanced by the new fork kit. But that requires splitting the tractor and my forks are in great shape so I'm gonna pass on that for the moment.

Good idea on the locking out of C. My point in locking out was to keep an inexperienced operator (read: 14 year old son, good neighbor borrower, etc.) from breaking the shaft or forks. I thought my machinist's idea of cutting the lever off (to reduce excess leverage) was a great idea, though I don't want to do that to mine.

Richard Easley

 

[Jim_Fisher]

Good morning, Jim --

The recess in the bell crank is exactly what I'm going to have him do that's what I meant the other day by chamfering and then putting an O-ring in that groove to contact the case sideways. However, I am unfamiliar with the term"quad ring." Can you tell me more about them?

Interesting what you say about the A-B shift being easier this is in keeping with the TSB on hard shifting it states going from C to B or A will be enhanced by the new fork kit. But that requires splitting the tractor and my forks are in great shape so I'm gonna pass on that for the moment.

Good idea on the locking out of C. My point in locking out was to keep an inexperienced operator (read: 14 year old son, good neighbor borrower, etc.) from breaking the shaft or forks. I thought my machinist's idea of cutting the lever off (to reduce excess leverage) was a great idea, though I don't want to do that to mine.

Richard Easley

Richard,

A quad ring is very much like an o ring but it is made from square or rectangular stock rather than round stock. A good hydraulics shop will probably have an assortment.

My thoughts on using the quad ring as opposed to an o ring are that it gives you more bearing surface and less chance of leakage. Any water that ends up on the quad ring will tend to run down the round part rather than laterally across the flat.

 

[mjncad]

Good morning, Matt --

I just looked up the article on Fortune's site -- no luck -- and then google, where I found the proper Fortune table of contents:

FORTUNE Magazine: Table of Contents - CNNMoney

. . . but the article isn't hyperlinked.

Sorry about that -- I figured that it would be on-line for sure . . .

Richard Easley

Thanks for checking Richard. Nothing is ever easy I'm afraid.

 

[reasley]

Quick update on the progress of the repair:

All of the parts ordered came in from John Deere On Wednesday. I took the new shaft and the shift levers to my machine shop Thursday AM -- first interesting find. The new shift shaft from John Deere is too large to use. That's right -- the original shaft is .625, the new one ranged across its length from .636 - .640 (.011 - .15 difference). No way would this shaft ever work -- it would not fit the new shift lever and fork that I ordered, nor would it fit the case. Of course, after measuring it, we knew all of those things anyway! My plan had always been to get the new shaft so that we could get exact length and distance from spring pin to spring pin measurements anyway.

The machinist noted that the shaft was not as polished as the old one and theorized that, when it was made, it never got finished -- explaining the larger diameter.

Got the newly manufactured shaft yesterday from the machine shop -- sans the O-ring groove. Will install today and get back to the list with more.

One other quick finding: got the TSBs from JD and another problem was uncovered about 4WD units, which requires replacement of gears. It, too, was a "cuustomer complains (under warranty, of course), we do the repair" they don't complain, we don't fix. Unbelievable for product defects. More on this later.

Richard

 

[mjncad]

Yes, that is correct -- it is installed backwards -- look again at M94864. Note how the lever butts against the transmission case? Mine doesn't -- it was installed with the lever about 2" out from the case, and that explains the continued angular strain on the shaft (keep in mind the built-in ridge on the shaft, too, right inside the case). Really ticks me off -- this thing has had undue stress on it since new because of an assembly error. [Note: the only other thing that would explain its incorrect attachment is maybe this was the original attachment method and the factory changed it over time, but I doubt it, because the picture in the manual shows the "correct" way and there is no reference to earlier differences.]
Richard Easley

I got a chance to look at my shift lever today and it sticks out from the transmission case about 2" too. Looking at the shift lever and its assorted linkages to the problem lever in question shows that if the lever were close to the tranny case, it would require additional bends in the shift linkage between the tranny lever and the shift lever.

In any case, I gave it a good shot of spray lubricant today.

 

[mjncad]

One other quick finding: got the TSBs from JD and another problem was uncovered about 4WD units, which requires replacement of gears. It, too, was a "cuustomer complains (under warranty, of course), we do the repair" they don't complain, we don't fix. Unbelievable for product defects. More on this later.

Richard

My JD dealer calls this type of warranty/recall a "Fix as found" defect. I had this happen when the original battery leaked and ate through the hydraulic oil cooler. I got it fixed under the recall; but only after my machine blew hydraulic oil all over the place while mowing a neighbor's yard one year.

 

[reasley]

I got a chance to look at my shift lever today and it sticks out from the transmission case about 2" too. Looking at the shift lever and its assorted linkages to the problem lever in question shows that if the lever were close to the tranny case, it would require additional bends in the shift linkage between the tranny lever and the shift lever.

In any case, I gave it a good shot of spray lubricant today.

Good morning, Matt --

I also concluded that -- re-routing is not really an option.

I completed the job today around 5:00 and the results are phenomenal. I've had this tractor (my first) for a little less than a year and the range shift has *never* shifted this easy. I knew that it always felt "sloppy," but I thought that this was because of the length of the shifter and assorted linkage.
Now, it is very, very easy to go all the way through from A to C without resistance.

What I ended up doing on sealing the case where the shift rod extrudes was to insert a nylon washer between the bell crank (lever) and the case of the transmission, with liberal amounts of lithium grease on the shaft at that area and also both sides of the washer. Before committing to installation of the washer, I carefully checked clearances with the top of the box still off. Interestingly, there was more than a 1/16" of clearance between the lever and the case when the shift lever inside the transaxle us aligned properly with the shift fork set.

After reviewing everything again and shifting it now that it has been repaired, here are my conclusions (some discussed earlier in the thread):

1) The shift shaft is a faulty design. Not only does the O-ring groove weaken the shaft, but it is:

2) within 1/2" of the outside of the case and this, combined with:

3) the "outside leverage" of the bell crank and:

4) the very long shifter that provides tremendous leverage

. . . is a broken part waiting to happen.

I believe that somewhere along the way, prior to my purchase of the tractor, the previous owner tried to forcefully change the range shift gears and this caused an initial bend at the O-ring groove. This bend, in turn, caused some of the shifting effort to be displaced into trying to overcome the resistance of the now-bent shaft, since that area is inside the case bore. This just became worse over time and eventually broke the shaft.

Richard Easley

 

[reasley]

My JD dealer calls this type of warranty/recall a "Fix as found" defect. I had this happen when the original battery leaked and ate through the hydraulic oil cooler. I got it fixed under the recall; but only after my machine blew hydraulic oil all over the place while mowing a neighbor's yard one year.

My mechanical experience has been in the automobile industry and I am quite disappointed in John Deere's handling of known defects. The MFWD TSB that I received the other day is even more disconcerting to me than the shifting problem. Basically, there is a maximum difference tolerance in speeds between the front and rear axles of less than 5%. However, many of the tractors that left the factory have been found to have a difference of greater than 5% with some tire combinations. If your tractor (4100, 4200, 4300, and who knows if there are any more) is affected, then it can cause excessive wear in the gears, to the point of requiring replacement.

To me, that is clearly, clearly, a product defect and should have been recalled.

Richard

 

[mjncad]

Richard:

Glad to hear you got your rig back online without having to split the tractor. Should mine ever punk out like your did; it's a relief to know the repair can be done at home should I need to do it, and that the redesigned forks work better along with your machinist's improved shaft and lever.

Based on what you describe of the replacement lever you received from JD; it sounds like JD outsourced replacement parts manufacturing to our good buddies in China. That's a heck of a difference in dimensions you measured.

Matt