Lot of good info there.
Aren't the Torson 3.73 differentials hard to get now? I realize you said 4.10 I'm just mentioning it because guys that build cars were saying they can't find the 3.73 very easily.
If I limited the search to FX4 Level II in the newer trucks or '97 if it were really nice (it'd be quite a bit cheaper I think) that would sure cut down on the ones that qualify.
Yeah true about the older 4.0L I have to remember that.
Looking at trucks online is probably just good in terms of seeing what the market thinks things are worth. But unless it's close, the chance of me driving 500 miles or something is about zero. I'd want to see the thing in person that's for sure.
When did they start with the torsion spring deal? My '99 has the SLA but it has coils.
Ford offered two different torsion differentials (if I remember correctly), one is gear driven (the better one in my mind) and the friction plate model. There is a third style that I can't remember the manufacturer has an S-shaped spring in the middle of the differential carrier and maybe some friction plates as well but I'm not sure. The latter two aren't as strong and the clutch plates eventually wear out and need replaced. They also need the friction modifier. Not a huge deal since many gear oil manufacturers include the additive in their oil but check to make sure.
I believe the "regular" FX4 model came with the friction plate design and the standard 28 spline 8.8" rear axle. The Off Road model may have had that same setup as an option.
As far as the gear ratio, 3.73 in a V6 should be pretty common. It's the best compromise between power for towing, hauling and driving off road and fuel mileage. They shouldn't be hard to find. As far as 3.73:1 gears in the aftermarket world, they should be available but I haven't looked for them either.
Not many V6 Rangers came with 4.10:1 gearing. If you plan on stepping up to 31" tires, I would strongly recommend looking for a truck with 4.10:1 axles. Those will give you about the same performance as 235/75R15 or 30" tires will. If you plan on driving off road regularly, 4.56:1 will be a better choice but those do not come form the factory. That gear and tire ratio will give you the best performance for off road, hauling, and towing but your fuel mileage is going to take a hit.
The Torsen limited slips are harder to get but available for the rear axle. The front SLA axle model only gets done in limited runs off an on. You would need to check with Torsen on if they have any left from the last run. I don't know what is out there for the D35 TTB.
The torsion bar suspension started in 1998. As far as I know, all 4X4 Rangers came with a torsion bar suspension. There was a kit made at one time that used coil over shocks to eliminate the torsion bars. So, that may be what you saw.
If you are looking at lift kits, you are still going to have to go with the kit designed for torsion bar suspension trucks. The brackets, knuckles and other bits are designed to bolt up to that frame only. TTB kits will not work.
From your profile, it shows you have a Mazda B3000 RWD truck. That would have coils and no SLA front differential. Unless you are talking about another truck.