I have a D4 7U28085 tracks are shot my pads are ok. I purchased a scrap Cat for decent chain, front idlers and lower rollers. What is the easiest way to repair rear sprockets? Is there a way to weld new tooth assemblies on without removing the track frame?  

Also try here if you want. He makes inserts for the sprocket teeth. www.manta.com/c/mmdjxfq/pigeon-products-mfg.
Does a good job, lots welding. If you are handy you can make your own liner inserts.

Good luck

I dont like welding near bearings or close to an engine, I have seen [not my machines] where bearings were "arc'ed" or pitted from welding on the machine.

You have to be careful to welder ground placement.

place the work lead close to the weld and have a spot ground nice and clean for it to get a good contact. it can be a good idea to shift it for each weld many bad welds can happen due to poor prep and crook earth clamps the best are one that are a proper clamp and not just relying on spring pressure. remember electric current will always flow to terra firma by the path of least resistance.

when i welded my new sprocket rims on I moved the ground lead to each spoke as i welded the rim to that spoke

Not sure proper name - Beam Clamps with a bolted on ground wire and ground clean clamp area work great and easy to move to new spot.

dpendzic, What did you mean by welding sprocket rims on? Is that a part I can purchase if I do remove the track frames? I guess I think I'm looking for the best solution, I just thought maybe there was a ring with bolt holes available to cut old sprocket tooth ring off, weld ring with bolt holes on old sprocket and then bolt tooth sections on? I must be dreaming right! Vic

Both Berco and Cat had new sprocket rims==I went with Cat as they were a little cheaper---I don't know if rings with holes are available for these old machines---newer machines have a sprocket with holes to bolt on sections of teeth---as Neil said you can cut a section out of a new rim and slide the rim on and then weld the section back in---the other alternatives is build up the teeth with weld or weld inserts in the old teeth