Damaged spline on axle shaft of the 420

[Lu47Dan]

I finally got around to building the puller to remove the bull gear from the old broken final drive from the 420 . The gear pulled with a little push from the portapower cylinder . Once I got it apart I discovered that the spline was beaten wider on the axle shaft , the old broken gears spline looks to be in fair shape . When I was counting teeth on the bull gear on the left side I noticed a little slop in the bull gear , The gear must be cast steel and harder than the shaft for the splines on the axle to be hammered wider by the splines in the gear . What I have been thinking about is to tiq weld the metal back into the splines and have them ground back to factory spec's . Or would it be better to just get another axle shaft ? As I still need to finish tearing the left side final drive apart , I am just trying to get ready for the bad news . Dan

[Lavoy]

If you have any rotational slop, it will not hold. Imagine the foot pounds torque on that axle in low gear and you can see why there can be no play. If you want to reuse the old axle, I would clean everything up spotless and grease free. Then use JB Weld, or Titanium Putty on both sides of the spline, and on the flat portion of the spline on both the axle and bull gear. Between the void filling and adhesive properties of either on, you will probably be fine.
Lavoy

[jdemaris]

. . . The gear must be cast steel and harder than the shaft for the splines on the axle to be hammered wider by the splines in the gear . What I have been thinking about is to tiq weld the metal back into the splines and have them ground back to factory spec's . Or would it be better to just get another axle shaft ? As I still need to finish tearing the left side final drive apart , I am just trying to get ready for the bad news . Dan

If there's engough metal in the splined areas for driving - and you just need to remove the slop - Deere Company sells metal-epoxy repair kits. These kits were usually used for outboard use - on worn axle splines where axle-hubs attach. Used on many old crawlers, wheel tractors, and 440 and 540 log skidders. It does work - we used it on many 2010s and 440 skidders with loos hubs on axles.

The epoxy Deere used - and maybe still does to reclaim worn splines is Devcon Metal Repair (steel or titanium). It tests as being stronger than any epoxy that JB sells (long cure or quick).

Devcon specs:
Cured ASTM D2240 hardness - 87
ASTM D638 tensile strength - 4000 PSI
ASTM D790 flexural strength - 7700 PSI
ASTM D695 compressive strength 18,800 PSI
ASTM D1002 adhesive bond/tensile shear - 2000 PSI
Maxium service temperature - 350 degrees F
Cure time - 16 hours

[jdemaris]

I got looking on my part's shelf. The kit Deere used to sell with the Devcon steel-epoxy was Deere part # AT33536 and came in a 1 lb. container. Some of the kits I have are 15-20 years old. I see now that Deere subs the part # over to AT76136 and it costs over $70. I have no idea what that $70 gets you now - I suspect it may not be the same as the Devcon product they used to sell.

[Lu47Dan]

jdemaris , thanks for the information . My dealer lists the kit and has three in stock will call them and find out what they include . I hope it is not like some of the repair kits I have bought in the past . They were good kits would have been better if they included instructions . Looks like the way to go for now .
What I can never understand is how people can run something to the point of this kind of damage . The crawler must have had a lurch to it when changing directions with as much slop that is in the splines .
Back to designing the fire box for my outside hot water stove . Dan

[Lavoy]

The Devcon is good stuff, I have the Titamium Putty, seems to me for a very small container and the activator I paid over $40 a few years ago.
Lavoy

[Gil]

New addition to an old thread. I saw that a guy on eBay was selling 2 pound kits of Devcon Titanium Epoxy Putty for $100 plus $20 shipping, a little over half the normal price. My understanding is that it last on the shelf for a good deal of time, so I thought I would buy this larger kit to try..

I plan on doing the traditional bull gear to axle wear repair. My QUESTION: do you clean both the axle and the bull gear surfaces or do you coat one piece with a release agent or oil film so that the putty only fills the void and the two parts are not "welded" together.

If you do epoxy them both together, how do you separate them if you need to later? Thanks Gil

[Lavoy]

I clean them spotlessly clean, no petroleum residue of any sort. I use no release agent, the bonding effect to me is just as important as the void filling aspect. You need to have all your ducks in a row, because once you start, you need to go til you are done. Bearings installed, preload set, and completely assembled in one rush, no do overs.
Lavoy

[Gil]

And what type of luck do you have taking them apart later? I mean like in a year or more. Gil

[Lavoy]

Never taken one apart. My theory is they hold, and if the final is rebuilt correctly, there should be no reason to take it apart again. If so, then heat is the answer I would guess.
Lavoy

[Gil]

Thanks. I did read somewhere that heating to 250 deg F will allow a gear disassembly of Devcon with a gear puller. However, I like your other theory: I'll never need to take it apart again! Gil