D4 undercarriage

The only thing that is the same is the 6.75" pitch.
D4 bushing diameter is 2.0", the D4C 2-1/8" diameter.
D4 sprockets are 27 tooth, The D4C is 29.
The pitch diameter is also different, 29.2" on the D4, 31.33" on the D4C.
D4 grouser bolting is 1/2", the D4C is 9/16".

Thank you for the information.I did'nt know there was that much difference in the tracks.Will they work?Also what is the "pitch diameter".I assumed that if the pitch and width was right I'd be fine.Worse come to worse I may have a very good 7U undercarriage for sale.Thanks again

Pitch diameter is basically how tall the sprocket is. Going from a 29 tooth down to a 27 tooth with the pitch remaining the same 6.75" results in a smaller sprocket.

The D2's have a relatively small sprocket compared to most other tractors. Sort of gives a rocking horse appearance if you look from the side. They also have the track frame pivot shaft in front of the sprocket so that may be one reason it was done that way. In general most improvements to the track systems from the early years result in more track on the ground and improved stability vs less track on the ground and easy turning the original designs had.

Sprocket pitch diameter is the centerline diameter of the track/rails as they wrap the sprocket.
Sprocket tip diameter for the D4 is 30.19", the D4C is 31.74"

Check your sprocket part number on the D4C. Apparently there are both 2" diameter and 2-1/8" diameter bushing versions used.

Thanks,I'll do that.This is a very early D4C serial 3xx,not sure exact,but before serial 400.

It would be unusual that it would still have the original undercarriage tracks/sprockets.

Also note part number if it has a weld on sprocket rim.