4.10's, like 'em or hate em?

[82F100SWB]

The rear diff in my powersmoker decided the gearset's life is coming to a close after 300 miles of towing on the weekend(almost 220K on the truck), it's not dead yet, but the howl says it isn't far off.
I managed to score a 4.10 geared 60/10.25 combo out of a 65K mile 97 for cheap(traded a winch for the diffs plus cash, and I had traded a 60 housing I got free for the winch) and I'm going to get at least the rear in this coming weekend.
I have never driven a PSD with 4.10's ever. I'm thinking it'll be fine with my summer 35's and it's going to be much happier towing, but, my winters are 235/85's. I don't want to kill what fuel mileage I do have.
I have a 3.54 R&P I could put in the front, but, I don't have any other long pinion 10.25 gears, just another set of 4.10's. Is the difference in fuel mileage worth buying another set of gears, or not enough that it would pay for itself?

 

[94f450sd]

youll be happy with the 4.10s.i forget what i was getting for mileage with mine but it wasnt anywhere even close to as bad as my idis were.mine has 4.10s and i run 235/85/16s year round on it.

but honestly i could care less about fuel mileage as long as its better than the 460s i used to run.

 

[Diesel_brad]

I have 4:10s in my CCSB w/ 315s and it as about PERFECT for towing. I do kinda wish i had 3:55s for empty highway driving but they would suck for towing with 35s

 

[94f450sd]

honestly im kinda biased toward the 4.10s.when i got my license every 1 ton truck i drove had 4.10s.we had a 72 f350 that we think had 3.73.it would run the highway with a 428,4speed at 80 all day and loved it.also had an 87 f350 with 3.55.they sucked!!!would cruise nice but had no sack with a 460.

 

[snicklas]

I have to agree with the 3.73's also, if they are an option. They seem to be a good compromise. I have them in my Excursion... and I still have the towing grunt I need, but running down the interstate ~70mph = ~2000rpm........

 

[94f450sd]

3.73s are a nice all around gear.not too low and not too high.

 

[Black dawg]

are you sure a bearing kit wouldnt fix it up?

 

[Diesel_brad]

But 3:73s were never an option in a 10.25/D60. so you would have to buy all new gears and install kits for both axles. By the time you spent all that money you would be better of using the 3:55s or 4:10s

 

[towcat]

another vote for 4.10's
there's no substitute when pulling heavy......well there's 5.13's but they're really obnoxious on the freeways.

 

[82F100SWB]

are you sure a bearing kit wouldnt fix it up?

No, there were nice big flakes of gear material on the magnet, not bearing material, a bearing kit might patch it up for a while, but the gearset is damaged.

I'm going to swap the rear in over the weekend, and probably do the 60 in a few weeks, need to get new spring eye bushings and the likes, I have a set of F350 springs that will get swapped in with it.
I'm thinking I'll probably like the 4.10's for the rest of the summer, the winter may be different. Next on the list is a new HPOP and injectors, drove a bone stock 96 on monday with a sub 30K re-man engine in it, and it'd flat out destroy my truck. I've been thinking I have had a weak HPOP for a while, especially towing it seems to fall on it's face much past 22-2300, more noise, but no real power increase, and the injectors, I know I have one or two that are questionable, the idle isn't the smoothest.

 

[fuzzydog]

I'm going to buck the trend and speak out in favor of the 3:54's

I used to have a 91 F250 with 3.54's and I would haul a heavy camper and pull a flatdeck with a Jeep Cherokee on it. I never won any races but I always got there with reasonable mileage.

Recently bought a 95 F250 with 4.10's and drove that for a bit trying to decide which I like best and the 3.54's won out - I swapped the 91 axles into the 95 (I had previously put a D60 in the front of the 91 so that was a motivator too)

I have been using the 95 like I used the 91 and still I won't win any races but it gets me there at a reasonable cost. And when I'm empty, well.....

 

[OLDBULL8]

Are you using 80-140 synthetic in the differentials, that's the recommended, comes from the factory that way?

 

[82F100SWB]

4.10's have been in for almost a week, fuel mileage might be a hair better, it's a little bit peppier, but, overall is isn't really that noticeable. My 6.9 with the turbo still on it would have walked all over this thing. I really miss my poor broken dodge right now.

As for gear lube, I'm pretty sure the 75W140 spec only came about with the Super Duties. I've been running 75W90 synthetic in my Sterlings for 10 years and many hundreds of thousands of miles(3 trucks combined) without ever having a problem.