Flywheel ring gear

[Lew Best]

Hey guys

The time has come where I have to change the flywheel ring gear on my 420 JD. Can’t find a “good spot” on it to start it again.

Probably been over 20 years since I did the last one; first off what’s the best way to get the old one off? Can’t recall if I cut it or if I heated it to expand it so it would slide off.

Secondly; I recall heating the new one to make it go on but can’t recall if I heated it in oil or just kept circling it with a torch to make it expand. Sure don’t wanna mess it up; the new gear is a little over 100 bux with shipping!

Any suggestions appreciated.

Lew Best near Waco, TX

 

[Bob]

Since you are REPLACING the ring gear, take a hammer and cold chisel, and cut the gear nearly through at several points around it's circumference. This will expand it enough so it will fall off.

Put the new one in a pre-heated oven, set as hot as it will go. After 20 minutes or so, grab the ring gear with oven mitts, or suitable leather gloves and drop it on the flywheel, which you have sitting near the oven.

It will fall into place.

To make it even easier to slip into place, put the flywheel in the freezer for a few hours, until just before the ring gear is done "cooking".

 

[Lew Best]

thanks!

Lew

 

[Andy Motteberg]

If you just want to flip the ring gear so that the good teeth are being used, just heat it up hot to expand it and remove it. Flip it and install, let it cool. As the hot ring cools, it will shrink and tighten down. If you are just going to replace the ring gear with a new one, you can cut off the old one.

 

[Mike M]

Just lay the fylwheel down and take a big punch and a hammer and start driving that old ring gear off.You may need to put blocks under it. Just go evenenly all the way around. They come off very easy. No need to destroy it like the other posted ways will do.
To install just clamp vise grips on the outer edge and heat evenly until spit sizzles good on the metal.Then it should flop right on. Have hammer and punch ready just to be sure it is seated before it cools.

 

[JDemaris]

If you heat before installing it will displace less metal when going on and be a better fit.
Some new ring gears can break if you try to drive them on cold.

At our Deere shops - we heated new ring gears in open air with a rosebud on a torch. Did not get hot enough to turn color - just hot enough to expand and go onto the flywheel.

 

[almrm]

Lew,

Thanks for this post as I have the same task to do on my 440I. In my case I have to remove the 74 loader and the backhoe to split it in two. Thanks to all for the great advice. It would seem to me that that this would be a good time to refresh the clutch if it is not in the first half of its life. Is ring gear wear a common problem with these engines? Maybe it is the utility nature of the typical work that causes many more starts per day than row crop tractors.

Mark

 

[Mike M]

Those models are HARD on ring gears mainly because the starter drive engages just by flying out as the starter turns.

 

[derbynut]

I recently turned one around on my '46 B because I couldn't find a new one and heating to remove and replace just as posted makes it very easy. I would add one thing no one mentioned: I like to use a brass punch to remove and a brass hammer to replace the gear. Not good to start off with damaged teeth, that will come soon enough.