I thought i would offer what seems to possibly be a not so uncommon problem and how to fix it temporarily.  The symptoms are as follows. When you pull back a steering clutch lever and the dozer is leaning toward that side, it could be either or both, the clutch sticks open, but if you get the dozer back to level and you pull the lever again it will release. Also, there is no click when the clutch lever is first pulled and the clutch lever will pull harder as the counterbalance spring is not being activated.
     If you take the clutch cover off you will be able to pivot the rearward linkage toward the problem side. What has happened is the rearward linkage has broken and is pivoting to the downhill side and catching on the casing. When you get back level the broken linkage moves toward the center and frees up. To fix it properly and get the counter balance spring back in play you have to remove that big casing that goes from the rear of the dozer to the rear of the engine and replace that linkage. But to get by, you can pull the pin and front half of the broken linkage.
     The first pic is of both clutches engaged; the second pic is of the left clutch stuck disengaged because the broken rear shaft is broken and has pivoted to the downhill side and caught on the casing. The third pic is a closeup of the stuck left clutch. The fourth pic is of the removed broken rear linkage. The fifth is a picture I took from a you tube video by Pacific  Northwest Hillbilly of his rebuild of his D4 7U.