Swapping 955 undercarriage

Sounds like someone has played mix and match. By your s/n's the undercarriage should be the same with the change to D6 undercarriage components coming in at s/n 12A5793. Either way if the whole undercarriage assembly fits one, it will fit the other as well. Sprockets will also need to match the swapped undercarriage.
Nothing is easy working on a loader.

So what possible undercarriage would be under my 58? Would it be easier to change sprockets or whole final drive assemblies?

I have no idea what you have for roller frames. Nothing I know of has inner frame rails that extend past the final drives. Maybe some pictures would help with identification.
As far as sprocket vs final drive assy change out you get to choose between sprocket pulling equipment or lifting equipment to do the job.
Pulling the sprockets would at least let you check out the condition of the splined hubs, the sprocket fit to the hubs and the bellows seals.

The later 12A with track guiding guards also had a guide on the inside going back part way under the final drive, but it could also have been added by a previous owner some time in the past.

Thanks, I will post pictures next time I get a chance.

if the one machine is strictly a parts machine, then you can cut the good sprocket rim off and weld it on the other machine and swap the track, might want to swap out the rollers as well. it has been done many times by others on the forum that have a good runner and a machine with good undercarriage for parts. on a loader machine, it is easier to work on undercarriage then it is to swap the engine.

there were some good conservation mabulas uploaded and stored in the technical archive, i think Josh put them up? someone will help out here. Mike Myers did this exact think on an old 2h RD6 while the sprockets were still on the machine. Not sure if that story is on this forum or the ACME forum, had very detailed pictures.

[quote="rmyram"]if the one machine is strictly a parts machine, then you can cut the good sprocket rim off and weld it on the other machine and swap the track, might want to swap out the rollers as well. it has been done many times by others on the forum that have a good runner and a machine with good undercarriage for parts. on a loader machine, it is easier to work on undercarriage then it is to swap the engine.

there were some good conservation mabulas uploaded and stored in the technical archive, i think Josh put them up? someone will help out here. Mike Myers did this exact think on an old 2h RD6 while the sprockets were still on the machine. Not sure if that story is on this forum or the ACME forum, had very detailed pictures.[/quote]

Seems to me there was a post a while back about a fellow using 10-24 or something similar screws and washers to hold the welding grove spacing and alignment until he got the replacement sprockets tacked in place on the machine.

[quote="rmyram"]if the one machine is strictly a parts machine, then you can cut the good sprocket rim off and weld it on the other machine and swap the track, might want to swap out the rollers as well. it has been done many times by others on the forum that have a good runner and a machine with good undercarriage for parts. on a loader machine, it is easier to work on undercarriage then it is to swap the engine.

there were some good conservation mabulas uploaded and stored in the technical archive, i think Josh put them up? someone will help out here. Mike Myers did this exact think on an old 2h RD6 while the sprockets were still on the machine. Not sure if that story is on this forum or the ACME forum, had very detailed pictures.[/quote]

Seems to me there was a post a while back about a fellow using 10-24 or something similar screws and washers to hold the welding grove spacing and alignment until he got the replacement sprockets tacked in place on the machine.