LCAM-01XA
Full Access Member
Supposedly the 1983 model year T19 transmissions were the only wide-ratio diesel 4-speeds available from the factory, at least based on info from members here who've had them. Those would have 5:1 first gear, still not a true creeper gear like the NP435 or the T18, but better than the close-ratio 4:1 for sure. Actually with 4.10 gears the 4:1 is manageable, less than ideal but not too bad. Keep in mind the 4-speed reverse gear is always a creeper lower than 6:1 so at least that part is never an issue.
Then the older diesel ZF5 (the S-42 model) has not just the 4:1 first but also a 3.something reverse, first is again manageable with 4.10 axles but reverse is horrible when trying to move a load. The later ZF5s that were used behind powerstroke engines (the S-47 models) can be had with a wider gear ratio, those have a 5:1 first gear and similar reverse - they are decent, but also quite sought after, so finding one for cheap is pretty unlikely.
The factory LSD is a Dana Trac-Lok unit and is somewhat of a hit or miss affair - it's better than nothing at all, but it's not as good as a full auto locker like a Detroit or something similar. In our IDI we have one in both axles (same basic design is used in both Sterling and Dana 60 axles, very close in dimensions too), the front one is the newer version with actual clutch material on the discs and it holds very well even with the weight of the engine right on it, the rear on the other hand is the older steel-on-steel model and it's kinda weak and allows one wheel to start slipping even when both are on relatively low-traction terrain (say one side is on loose dirt the other on grass and there's nothing in the bed, the grassy side will slip). For a truck that's gonna spend quite some time on paved roads you probably want the factory LSD cause tires ain't cheap these days, but for a farm truck that will mostly see dirt and mud and grass and such I think a simple welded open diff would be a better choice as you will always have both wheels spinning no matter the terrain. And a long-wheelbase nose-heavy 2wd diesel truck will tend to get stuck quite often so you really wanna give it every fighting chance you can, that can include even tire chains if ground is soft and grabby tires alone ain't cutting it.
Then the older diesel ZF5 (the S-42 model) has not just the 4:1 first but also a 3.something reverse, first is again manageable with 4.10 axles but reverse is horrible when trying to move a load. The later ZF5s that were used behind powerstroke engines (the S-47 models) can be had with a wider gear ratio, those have a 5:1 first gear and similar reverse - they are decent, but also quite sought after, so finding one for cheap is pretty unlikely.
The factory LSD is a Dana Trac-Lok unit and is somewhat of a hit or miss affair - it's better than nothing at all, but it's not as good as a full auto locker like a Detroit or something similar. In our IDI we have one in both axles (same basic design is used in both Sterling and Dana 60 axles, very close in dimensions too), the front one is the newer version with actual clutch material on the discs and it holds very well even with the weight of the engine right on it, the rear on the other hand is the older steel-on-steel model and it's kinda weak and allows one wheel to start slipping even when both are on relatively low-traction terrain (say one side is on loose dirt the other on grass and there's nothing in the bed, the grassy side will slip). For a truck that's gonna spend quite some time on paved roads you probably want the factory LSD cause tires ain't cheap these days, but for a farm truck that will mostly see dirt and mud and grass and such I think a simple welded open diff would be a better choice as you will always have both wheels spinning no matter the terrain. And a long-wheelbase nose-heavy 2wd diesel truck will tend to get stuck quite often so you really wanna give it every fighting chance you can, that can include even tire chains if ground is soft and grabby tires alone ain't cutting it.
