New sprockets contact final roller on 420c

[jk]

Hi, I've been buying parts from Lavoy and periodically checking the message board for a few years, and now I'm finally going to tackle the tansmission input shaft that needs replacing. During the tear down I tried my new (solid gold) sprockets on. I had to slack the frame to final drive bolts and spread the rear cross member from the final drive with a porta power to get them on, and they still hit the last roller. The axle bearings need a little shimming, but nothing that seems drastic enough to create the problem. The rollers have button style grease fittings, and I assume they are the correct part.
I was thinking about turning the crosstubes upside down, in case they're bent, but that seems like alot of work for something thats not likely. This is a pre 100,000 sn 420c by the way, and has wide snowtracks set at, I believe 46" and there is an outside blade that mounts on the overlength front crosstube and bolts into the end of the rear crossmember....so it has taken some hits out there, no doubt.
I'm also wondering if there is enough meat on the roller that I could turn a quarter inch or so off the center?
I've seen sprockets hit the roller on someone elses machine, but his answer was to let them "wear in". With new sprockets (the last in the JD inventory, I was told a few years ago when I bought them), I'm hoping for a better solution.
Anyone have any experience with this problem? Clever ideas?

[Lavoy]

I have run in to this on a couple of 40's, and a couple of 420's below 100,000. What it has always been is the side frame has moved rearward because the nuts that hold the sideframe to the clutch housing have not been kept tight, or the bolts have broken. This allows the side frame to mover rearward and causes to little clearance between the sprocket and the roller. There is absolutely no way that they were designed to be "run in", I can't believe that someone actually told you that. There is something wrong someplace, you just need to find it.
Look at your holes in your sideframes, and see if they are elongated. Also look at the nuts that are on there. What many people do not realilze is that on these crawlers, the nut HAS to be on the outside. Additionally, you can NOT use a standard nut and lockwasher. The correct nut is a lugnut for lack of a better term that has to seat in the conical seat that is machined into the sideframe. Using a standard nut allows the sideframe to work back and forth and slot the hole out. At one time I had one crawler that this had happened to so badly that the sideframe had worn a groove in the front of the final drive case, and the sprocket had hammered the roller to death. There are other possiblilites, but I would be this is the problem, or at least part of it.
Lavoy

[jk]

Thanks alot Lavoy. I guess I was thinking there was some additional problem because things were still hitting after backing off the frame to housing nuts,and pushing apart with the porta power. Probabley not though, because there has been some welding around the frame holes, and things may not be able to get back where they should be. Definitely doesnt have the correct conical nuts...also one final drive has only half a hole; the ear is busted.And yes the frame has worn into the housing alittle.
I think I know where there is a 430 frame set. Is it true 430s use 4 bolts each side instead of 2? Would 430 frames work on the 420?
Alternatively I guess I could fashion a plate with some kind of robust self centering bolt holder, set everything where it appears to belong, and then weld it on, scabbed over the old frame? I presume the frame is steel and is weldable?
How did you deal with it Lavoy? Are the conical nuts available?

[Lavoy]

420 after 100,000 as well as 430 and 440 used four bolts per side, as well as a double plate. Yes they will work on yours, you need to change the clutch housings as well. The nuts were availalbe a few years ago, have not checked in a while. If all else fails, a 5/8" fine thread lug nut that uses a 1" socket will work fine.
I know on one 40, the side frame was so trashed, I cut out the lower section with a plasma cutter. Then I jacked everything back in place, cut a plate to fit with the hole in the proper place, bolted the plate tight with the correct nut, and then welded the plate in place.
Also, look close at both of the crossbar clamps to make sure they have not come loose or broken the rivets, this can contribute to the condition as well.
Lavoy

[JimAnderson]

JK,
I ran into the same problem with my first JD crawler.The side plates are
steel and can be welded.I welded the holes up and removed the studs in the clutch housing.I then ground the ears on the housing so that I could
install a 5/8 bolt,drilled out the side plates to accomodate the bolts and
put the beast back together.That was over twenty five years ago and
they are still fine.Use a good grade of locktite and use grade 8 bolts.
The 430 crawlers used a four bolt side plate.You can bolt them to
the older clucth housing using the upper and lower holes only.
One thing I found with the older two bolt style side plates is a
tendancy to crack just foward of the bottom bolt holes at the point they
bolt to the final drive housing.JD solved this problem by adding an inner
steel gusset on later side plates.You can weld up this crack but it
will come back if you work the machine.Hope this helps.
JimAnderson

[sbarr]

Yep had the same problem,I made up a sort of stepped washer to take up the wear in the hole in the side plate,then welded it to the plate ,I even had to re-tap the housing to the next size bolt cause of wear,boy was this old crawler used hard in its early years.

[jk]

Lavoy, Jim and sbar,
Thanks for the input. This gives me some confidence and several good options. I appreciate the details in how you all approached the repair. Sometimes it's easy to miss the obvious, and sometimes it's not so obvious how things will stand up over time. Think it's best to leave my options open until all my problems are out in the open. Jim, my machine has a crack at the rear frame to crosstube connection just as you mentioned. It's helpful to know the later frames were reinforced while I'm weighing whether to replace the frames with later ones or repair these. Guess I better check what the guy wants for the frames to see if that really is an option. Not sure I want to replace the clutch housings....but by the time I get the tranny apart, who knows? Thanks again for the input folks, I'm sure I'll be asking alot more questions before I'm done.
Thanks Lavoy for keeping this forum afloat.