Fan Shaft John Deere A

[Mike Keson]

Working on my 1952 JD "A" tractor I had a bad friction washers on fan shaft. I took the fan shaft out of the tractor and also found a bad bearing on governor end of the shaft. I had a tractor mechanic rebuild the fan shaft new from end to end. Now, I have a different whining noise from the fan shaft. My I and T shop manual wasn"t much help. Do I need to shim and if so, how much? Or, any other ideas.

 

[Paul from MI]

Yes, shim the fanshaft so the "heels" of the bevel gears match. This is controlled by the shims between the fanshaft and governor. Then adjust backlash by shimming the governor shaft L.H. bearing retainer. Should get rid of your noise unless the gears are baddly worn.

 

[Lee B]

A 'real' $80 manual won't help you much better other than being relieved of the $80 of course.

Yes, you probably do need to shim, but it might be in places you haven't thought of yet. The governor shaft also adjusts with shims on the left side bearing cover to loosen/tighten clearance between the big driver gear and the smaller driven fan gear. These two gears need to be set up in a similar manner to the way a pinion and ring gear are set up in an automobile rear end. It takes some talent, but not a vast amount.

The best tip I can offer is to reach your arm up inside the crankcase and extend the handiest finger up into the governor to feel the backside of the two gears where they mesh. If you can feel no step where the two meet then that's a real good starting point. Closer measurements are needed but essentially if you can get the slack down to .003 to .010 without any binding, you should close it up and give it a test whirl.

Test whirl might include a summer of farming to get rid of the whine entirely as some do and some don't. As long as the clearance is close to right and the two gears are engaging well, they will wear into one another to such an extent that the whine should go away eventually. Mine did with brand new gears.

Closer measurements mentioned above include the use of rocking shafts back and forth to detect the amount of slack remaing. A crude form of guesstimating, this technique reaches it's apex at slapping rocker arms around to listen to the click made by the slack in them and adjusting them based on the sound alone. Won't be so much based on sound in this case as much the feel and some experiance helps a lot. Perhaps your mechanic might want to give it a try after reading this?

 

[F-I-T]

I think you should adjust the governor shaft location first. This sets the heel. Then you move the fanshaft fore or aft to set the lash. Right? And it's best to do thjis woth the governor case and fanshaft assembled on a bench....

 

[Mike M]

If your fanshaft bearing was bad then I'd say 99.9% chance the governor bearings are too.

The whole thing needs to come off to adjust it correctly. The Late B service manual shows this proceedure very well.

 

[Shawn MN]

I would pull off the governer plate on the flywheel side and check out the ball bearing. It seems to make noises from there that would make you think they are from else were. Been there, done that. Goodluck!

 

[F-I-T]

...BTW, here's an old post of mine where I describe how I rework gearsets to prevent unmatched whine...

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GNB:
The spec (which I do not have handy) is to measure the backlash at the intersection of the gear teeth. To do this, you would have to have the fanshaft and governor case dismounted and sitting on your workbench. Not an easy task.

If you knew the diameter of the gear on the fan shaft, and compared that to the diameter of the fan blade, you could say that if the specified fanshaft play was .005" at the gears, and the fanshaft gear was 4" in diameter (2" radius), and the fanblades were 24" in diameter (12" radius), then the .005" play would look like .030" play at the tip of the fanblades. Now the play will go all the way through the governor and then onto the cam gear to the crank, so one of the Deere Service Bulletins say that a Model A, B, G, or D should show about 1/4"-3/8" total play when the fanshaft gears have about .005" lash in them. That gets you in the ballpark.

If you do choose to remove the fanshaft and governor case to make the adjustment, there are a few things to consider. If you have ever set the heel and lash in a ring and pinion of a differential, then this will be familiar. If you have not, then it can be a bit vexing. You'll need a dial indiactor to do it right.

First you set the heel using the shims on the fanshaft side of the case. Add or subtract shims to get the edges of the gears flush. Then you add/remove shims at the governor shaft (flyhweel side) of the case until you get the correct backlash or free movement using the dial indicator resting on a gear tooth while you rock the opposing gear. After this adjustment, re-check the heel, rinse and repeat.

The I&T manual describes it better than I probably did, but that is the essence.

Now, since many of these gears have been run out of spec for many years, their wear pattern will probably be such that after a correct setting, the gears will whine and howl as they wring in to their correct wear patterns. The problem with this is that as they wear, quite rapidly at first, the heel and lash will be changing. One of the things that I do to alleviate this is to make the adjustment on the bench, and then rig the assembly on my drill press so that I can run it in by driving the fanshaft via the distributor drive lug. This way I can set it, oil it, run it, oil it some more, and when the whining finally begins to subside, I can measure the the heel and lash again, correct if necessary, and run it some more. Once the howling and whining has decreased substantially, I feel comfortable that it will not howl after installation, and that the gear sets will last for a good long time.

Also, if the gears are very worn, there will usually be a wire-edge burr on the teeth edges. Be sure to stone this off before you begin the setting and running in.

Hope this made sense.

Frank

 

[Mike M]

I think some may of even used lapping compound on the gears while running in their rigged up jig to hold the case and the fanshaft.

I have never tried this ( yet )the ones I had problems with was back many years ago and I either found really good used matched sets or bought new gears. New gears is sure the way to go if you can find them.

 

[F-I-T]

On tough ones, I use Clover 0000 lapping compound, which is SC in a grease base. You have to rinse thoroughly after you do this, then I finish with oil to hear it work as it will be assembled. Over on johnnypopper.com, I helped a fellow work out the lapping of a high tooth in a Dubuque transmission which had a repaired tooth that continually sang. He rigged itup wiht an electric motor and let it wring itself in. We used that technique on many, many gear heads on traversing horizontal milling machines.

 

[Mike Keson]

Thank you for all the good information and ideas. I talked to my tractor mechanic and he thought since I did not have any noise before rebuilding the fan shaft I should try a thick shim gasket between fan shaft and governor. While apart, I'll check for bad bearings in governor housing. Thanks again for all your help.