Starting up the sas project on the Jimmy. Only two options locally for axles to choose from and would like some opinions. 05+ SD Dana 60s (3.73/4.10) are the most common around me and can be had for a couple hundred bucks. Late 90s Cherokee Dana 30s are less common, but still available albeit they're 3.55 gears for the same cost as the 60s. I know I'll probably never wheel hard enough to cause issues to the 60s, so that's a plus. However, I'm intending this rig to be a cross country "overlander" and will see a good amount of highway, yet be prepared for mountain passes/offroading. Not trying to kill the mpgs too much. I will be replacing the drivetrain with a tuned 4.8LS, built 4L60e, and whichever t-case I can find to support this setup. Not looking to run anything over 33-35 tires. Is the 60 overkill? Will the extra weight effect the mileage significantly? Which gears would be best for either axle?

 

I've never done a SAS (yet) but personally I'd go with the option that is more durable, and involves less work. I think even 35's might be a strain on a dana 30, but you'd be extremely unlikely to break a D60 with 35's. Yes you can make a D30 stronger, but if both options are the same cost, a stock D60 is stronger and cheaper than building a strong D30. The extra weight of the heavier axle might be a hit to your MPG, but I think the benefits will outweigh the costs.

As for gearing, if the idea is setting up for off-roading, then you'll probably enjoy lower gears more. I wish my truck had 4.10 gears with the 32" tires I run. Even if I LS swapped, I still think I'd prefer the lower gears for off-road.

Just my

Just editing to say: Is the D60 going to be too wide for your purposes? Will the D30 fit easier? Are you ok with, or do you want a much wider stance from a full-size axle?

 

Along the same line of thought I've been having. Plus with the 60s it leaves room to grow should 33/35s end up too small.

I agree with lower gears, but would like the highway to not suck. I had a Zr2 with 33's back in the day with stock 3.73 and she moved just fine for me. I hear 4.10 and 4.56 are a good option for larger than 35s.

I don't think I'll struggle with the wide stance, in fact I'd prefer it I think. Looking at photos with other blazers/s10s with 60s doesn't seem too over the top. Was thinking of getting 4" baja fenders for the front.

 

As far as gearing goes, in my Sonoma with 3.73 gears and 32" tires I cruise on the highway at 110Km/h (around 70mph) with the engine at 2000RPM. It's probably the best point for fuel economy on flat ground, but in the hills and mountains, or in the heavy winds we get in my area it can cause the truck to hunt gears. If you were running 33's or 35's you'd be even lower. 4.10's would put me at about 2400-2500RPM, which I think would be in a healthy range for my driving style and needs. I don't drive faster than that with my Sonoma, I often tow or haul a load, and personally I'd rather have the lower end acceleration on the street and better crawling gears for off-roading that 4.10's would give me. I doubt I'll spend the money on it though.