4.10 or 3.73
 

98 4dr 4.3L running 31X10.5 and power train is stock except cold air intake
Wanting new diff gears
Still have my original 3.42 ratio,
Was going to buy the 3.73 gears to give it more grunt, then I noticed you can get the 4.10 gears cheaper, I have driven blazers with the 3.73 and they work very well on highway and off road.
What do you think it would work like on the highway with 4.10 ratio with speeds around 100kms to 130kms
Also looking into 32 or 33's next year so I want to keep that in mind as well
Comments welcomed!!!!!

Well if you are for sure getting bigger tires next year i would go with the 4.10's. With 31's and 4.10 gears you will have roughly the same speed to RPM ratio as you would with 3.73 gears and stock tires.

But if you are sticking with 31's then i would probably stick with the 3.73 gears. I guess it doesnt really matter either way, with the 4.10 you will do better in city but with the 3.73 you will do better on the highway. I have the 3.73 and i do just fine with 31's. But if you are planning on getting bigger tires then most definitely go with the 4.10

Hope this helps.

My blazer had 3.73 factory and while I'm not unhappy with them if I didn't have them and was gonna swap I would pick 4.10s over 3.73s.

The danas I've built for my sfa have 4.10s and my goal is 35s but ill have to see how it sits first.

3.73 gears put you back almost exactly with 31" tires as the stock 235's
with 3.42, i cheeped out and just replaced both front and rear diffs with
factory units from a $300 parts truck i found, the cost of gears plus the
bearing kit and install cost was way too much, and i got a g80 in the
process

with 32s or 33s run 4:10s. do it rite the first time.

I agree with pretty much everyone above. If you're sticking with 31's the 3.73 will be great. If you're planning on tires bigger than that in the near future then definitely go with the 4.10's. It sucks bogging down climbing a steep trail because your truck is geared for highway cruising.

Well after all of your contributions to this and many internet searches and research I have decided to go to a 3:73 and stay with 31s, reason is tires are cheaper fuel mileage will be better and looked at a lot of blazers with bigger then 31s and in my opinion they don't look right unless you install the big lift kit, which for me takes the blazer out of my daily driver class due to local restrictions, so as soon as I get the dollars to do both front and rear with all the install kits it will end up with a 3:73, Thanks for the help!

From my experience this is what I found:
31"& lower 3.73
32-34 4.10
35-38 4.56

Most talked about 4:10's & city & off road, not highway. Personally I wouldn't want a 4:10 gearing for highway even with 31's or 32's. I have 32's & a 3:42 gearing & it kicks into OD & TCC locks up & I'll cruise at 1700 -1800rpm at 65mph.
That of course depends on wind, trailer weight, tire pressure etc. But by itself I'll cruise at 1800rpm all day at 60mph.

<edit/afterthoughts> my trans has been upgraded with a TransGo Mr Shift kit, corvette servo, kevlar belts etc & the PCM has been reprogrammed for the changes I've made. But the gearing still holds true IMO.
Your choice is how much highway compared to city &/or off road you do & the costs in gas.

I still got IFS and I want to upgrade from stock gears to 4.10 or 4.56s. I got 35s and about 9"-10" of lift with a new CAI, catback w/ 2.5"piping and magnaflow Should I do both front and rear, what do I buy for the front gears if I do upgrade, and what is the most cost effective method of approaching this project.

*BTW I know im piggbacking on this post but y'all have had the best input I can tell so far