I think the issue with the hard steering D4 is that the booster springs are not adjusted properly. I don't think they can be set up without removing the transmission cover like PNW Hillbilly did. Even my 1939 1H D8 has booster springs and steers quite easily.

Thanks for all the replies, the dozer is a 1970 83j897 they modified the undercarriage to have bolt on segments, they may have welded a bolt on segment sprocket ring or used a d4c sprocket on it. I have a picture but don’t know how to post it. It has salt rails also.

I have this spring Assist kit of a D4 if anyone can use it. Skinner

Aha Mr. Skinner! Thank you for sharing. I did not have any proof of any booster unit for a D4 existed. Now I can say I told them so... I did not know the name, I thought all of them were Rivinius. The HD-5 orchard tractor I grudgingly bought has external boosters near the operators kneecaps. I will post when I get the courage to bring it to my yard. Thanks again, JM

Dancat, check your 7u out well before you throw in the towel. My 7u was night and day difference between the two levers. Figured the bearing was out going through the top cover on the hard one. Found out when I had the top cover off this summer that the spring was broken for the assist on that side. Nice used spring and some oil in the bearings and they are both the same again. It is possible that you have two broken springs or two siezed bearings.

At a stage I looked quite seriously into a modification to segments forthe D4 D/E. Could never find a segment with the same pitch and similar sprocket diameter to keep speed and load on the drivetrain about the same. I think I even looked into different pitch chains but that would still work with the standard rollers and idlers.