I'm running 3.55's with the stock tire size on the ORP 265/70/17. Paying someone to swap gears is steep. The best price I have been quoted is $1700. To keep cost down I was thinking of buying a complete salvaged front axle with either a 3.73 or 4.10. Was 4.10 an option? Can I simply unbolt mine and bolt in the different ratio, or are there other issues?
For the rear, I would do it myself or pay to have it done.
I want two improve my towing capability and the 3.55's suck with a heavy load. The transmission ratios don't work well. I also don't want to go too far. Would 4.10 be too much with my tire size?

 

nope, not from the factory. Maybe if you did enough junk yard searching you could find someone that did it aftermarket on a vehicle, and can buy the units from the junk yard

 

You wouldn't notice much difference with 3.73s. 4.10s would be noticeable. For heavy towing you might want to consider an even higher numerical ratio.

To know what rpm your engine would be turning with the new ratio compared to the old just multiply the existing rpm at a certain speed by the ratio of new to old. For example if you went to 4.10s, multiply the existing rpm at any speed by 4.10/3.55 to find out what the rpm will be after changing to 4.10s at the same speed.

 

Or use this calculator:

http://4lo.com/calc/gearratio.php

 

So much for the 4.10 swap on the cheap and easy!
Going to a 4.10 only concerns me because at 70 with OD off, I will be turning about 3500 rpm. That just seems too high. Realistically I wouldn't tow that fast often, but if I did, it just seems like too much. Also OD on would put me at about 2600 likely making my mpg worse.?
Would the benefit of a 3.73 be that minimal? Although it has been years since I drove one, my brother's LD f250 with a 3.73 and 5.4 was a beast out of the hole... from what I remember.
I can't justify dropping $1700 on this truck for gears knowing it will still have its shortcomings. Hmmm.

 

I did a swap to 4.10s and I cannot begin to tell you what a difference it makes towing, especially with a manual transmission. I remember when I had the stock gearing and what a dog the truck was, especially in reverse.

 

Your math is off. At 70 mph with 265-70-17 and 4.10's, it's 3050 rpm in 3rd. In OD it will be 2130. Your tire diameter is 31.6.

 

The numbers you are posting are about what I have now with 3.55's. Something is off!
I have no doubt 4.10 will help towing, but I also don't want to regret going to far for when I'm not towing.

 

Those numbers assume locked torque converter.

4.10's with stock tires won't be a problem on the highway. A 5.4 is good for 5400 rpm, that's where the rev limiter is. Without the limiter the engine is good for over 6000, but the tranny isn't.

3.55's to 3.73's are not worth the expense, there just won't be much difference.

 

Maybe it's your tachometer that is off.

 

your truck hasnt been recalibrated for larger tires right? So you're going faster then it is displaying. So your 70 is probably more like 74

 

easiest way to look at it is simple numbers

410-355=46

46/355=12.9 So about 13% difference from 3.55 to 4.10

So if you're currently turning 2100 at 70, add 13% so 2370 rpms

 

He said his tires were stock size. They are the stock size on my 02.

 

Correct. Tires are stock.
Tach and Speedo are as close as they were when it rolled out of the factory.

 

They won't be with a gear change, you will need a programmer to adjust that on a 99+, a different VSS gear on a 97-98.