Hi everybody - I'm asking the above question because the undercarriage on my 1980 25Y series 931B is shot - and I picked up in the Cat undercarriage dimensions section of the Undercarriage Conversion guide, that there's a weld-on sprocket rim available for the 931, that utilises a 6.75" pitch. The P/No for that weld-on rim is 6S7879. The standard undercarriage of the 931/931B is 6.125", and the D4 is 6.75" pitch - so I don't think this figure in the book can be a typo. So that just got me wondering - why would Cat produce a D4 pitch sprocket for the 931/931B, if there wasn't the ability to convert to D4 undercarriage? The strange part is, this is the only 6.75" undercarriage pitch component I can find listed for the 931/931B. You'd think, if they listed a sprocket with that pitch for the tractor, there would be other 6.75" pitch undercarriage components listed for the 931/931B. But all the track links/chains listed for the 931/931B are 6.125" pitch. I looked up the D4 roller dimensions, and it appears that they may be too big to fit the 931/931B trackframe, so all this has left me puzzled. Any useful advice/knowledge would be gratefully accepted.
The only place I can find any reference to 6S-7879 is under 81U (931), 82U, & 83U (D3).
I would have thought the 951 undercarriage is more likely to be similar to the D4.
I recall seeing a 931B (think it was a B) wide pad with heavy duty undercarriage that I think they said was D4 undercarriage.
My track manual shows the 6.125" pitch tracks used on the D3-931-935-D4B-D4C. It shows two different bushings possible, large stepped and a small diameter standard bushing. Possibly that is what is referenced. The D4-941 tracks are completely different in that the pitch is 6.75". This is probably a newer machine model than the D4C.