Swapped wrong axle?

[VcentG]

So first post but I've used the forum for a long long time as a stalker.

Anyway so I have a 97 ranger ext. cab 3.0 manual 2wd. A long time ago I lifted it and put 31s on it. I was poor so my friend and I went to the junkyard to pick out an axle to swap using the axle code. Didn't have any problems but now I'm using it as a pilot escort car and I've been looking into ways to up my mpg. Long story short I've been using calculators online and a speedo app (that seems pretty accurate in every car I've tried) to see that the gears in that truck may have actually been 4.56s. At ~2500 rpms my speedo says 60 in 5th and the app says 62-64. Using the engine rpm and speedometer calculators on Spicer's it seems like 4.10s would say I'm doing 72. And 4.56s would be doing... 64. So anyway I guess my "help" is is this likely the case of swapping the wrong ones or are these calculators outdated? I also looked up what my ranger SHOULD have for a tranny and it's final gear should be a .79 ratio. But again this is all internet. No under the truck looking.

And secondly. Is it worth swapping to 4.10s if they are the wrong ones? As in what mpg gains could I expect and also will it still maintain hill power? Or even get better? My OVERSIZE LOAD sign does catch a decent amount of drag so climbing some steep hills I can cruise at around 50 with ease yet can't really go much faster in 4th. Mashing the gas nets me barely an increase for 70% more pedal down. I barely have to push the pedal to.maintain 50-55. So would 4.10s make that easier or worse?

Edit: also currently sitting at around 15-19 mpg on these runs I guess depending on terrain.

Edit 2: the axle we swapped in has limited slip. Don't know if that means it will.be more expensive to swap.or what. My original did not.

 

[adsm08]

4.56s were not a stock ratio. You likely have 4.10s, unless that axle was swapped to 4.56 before you got it. 60 on the speedo vs 62-64 on the GPS is within the margin of error. That margin is given in percentage, rather than absolute numbers.

Also none of the stock ratios ended in a .79. The closest would be 3.73.

4.56 would make hill climbing easier over 4.10s, but will reduce highway MPG. The problem is that gears are expensive, so even driving a lot like you do it is going to take a long time to recoup the money you spend on gears in fuel savings.

I doubt any of that was helpful, I'm just having trouble getting my thoughts organized tonight.

 

[scotts90ranger]

Measure the height of your 31's, my guess they're closer to 29", almost all tires are much smaller than they say in the inch size... I don't remember back far enough for when my Ranger was on 31's with 4.10's... and my Explorer on 31's has a 4R70W with a taller overdrive and has 3.73's anyway...

 

[BlackBII]

Just for reference, I have 31"s and 4.56's and I'm at 2700rpm at 65mph on gps.

If you jack up the rear end and rotate the tires, you should be able to count the driveshaft rotations to see if you have 4.10 or 4.56

 

[VcentG]

4.56s were not a stock ratio. You likely have 4.10s, unless that axle was swapped to 4.56 before you got it. 60 on the speedo vs 62-64 on the GPS is within the margin of error. That margin is given in percentage, rather than absolute numbers.

Also none of the stock ratios ended in a .79. The closest would be 3.73.

That's what I'm saying though. The axle we swapped we only grabbed because the axle code said it was 4.10. But maybe the guy swapped it before his truck got junkyarded?

And for clarification the .79 was the transmission ratio in 5th gear which is required when using this calculator.
http://spicerparts.com/calc/transratio/index.html

As for the other posts (sorry on phone ATM so multiquote is eh). Edit. I'm dumb so I'll just measure the tires.

And BlackBll that sounds really close to where I'm at. I was hoping I'd post on here and it would be like "duh you idiot of course you have XXX" but I guess I gotta get dirty. I'll do that then.

Any clues as to if the 4.10s would mean I now cruise up hills at a lower speed than 50s? Because I do have to keep up with the truck I'm behind and depending on the load hills don't even slow them. And also we any clue on mpg gain? I only remember looking at charts saying 4.10s we're best for balance of power and mpg but I don't recall any saying if it's like 1-2 mpg or like something massive like 5-6

 

[VcentG]

Alright so update. 3000 rpm I'm at 76-77mph. 2700 area I'm at 70 mph and 65 mph for me is at JUST above 2500 rpm (gotta be like 2525-2550).

The information seems pretty damn accurate to what the calculators say my rpm's and speed would be if I had 4.56s. Like dead on accurate
http://spicerparts.com/calc/transratio/index.html
http://spicerparts.com/calculators/engine-rpm-calculator#
For instance in the speed calculator one 3000 rpm with 4.10s would be 85 mph. I was nowhere near that so it seems impossible. (have I answered part of my own question)

Didn't measure the tires yet because it's been a long trip across California but I know they do kind of "sag" when my trucks sitting (33 psi) so perhaps when rolling they are as well? *Shrug* They're new bfgs ats. Well new to the road. I bought them a year or so ago but my truck had some head gasket issues so it sat. Which is another reason all this info is vague to me. I lifted it and swapped the rear end so long ago.

So I guess all that's left is to manually check to see if the calculators are correct and see if anyone has any details on if it's even worth swapping.

 

[alwaysFlOoReD]

When you measure the tire, on asphalt, from the ground to the middle of the hub or axle, then times two. That will give a truer representation of tire diameter.

 

[Mac]

Saw this post earlier so when I went to town, at 70 mph with "31's" I run 2600 rpm.
Dave

 

[Mountain12]

Help

I am trying to find someone who will show me how to post.
My e mail is xxxxx.

Thanks
Ray

You have 2 posts on site so I don't understand your problem.
Until I find out if you're a bot you can't post your email publicly. Sorry.
Richard

 

[85_Ranger4x4]

With 31's and 3.73's I run about the same RPM at 60mph, around 2700rpm.

I also have a three speed automatic transmission with no overdrive...

Post your pics somewhere like Flikr or Imagur and remote link them to here.

 

[fastpakr]

Honestly, I wouldn't mind a bit running a 3.0 with 4.56 and 31's. You're not going to lose much in highway MPG and it's great for running around town, getting a load moving, or starting on a steep hill. Seems like a great selection to me.