Thanks everyone, I think I'm going to go with the one out of the 96 F250, 4.10,PZ with 132,229 miles for $400. I will need to take a drive to Spokane to pick it up. Hope to get it next week.

 

What transmission do you have?

E4OD with 5.30 gears would run 70 MPH at 2870 RPM in overdrive with 235/85 tires.
The metric bolt pattern would mean 2 spare tires required, one for the front axle and another for the rear axle, but it should be a pulling beast for a NA 7.3.

Any of the 97 back to 88 axles will have the speedometer sensor and the same bolt pattern on the wheels though.

 

I have the E4OD and 235/85 tires. I do not like the idea of two spares. If I understand you correctly the axle I listed above (96 F250) will take a different wheel. This would mean I would have to buy three wheels for the truck, two for the back and a spare. That would raise the cost.

I'm looking for a simple switch without any fabrication work if at all possible.

 

The 96 will have the same bolt pattern, the 99s and up are different.

 

Ok, good. Can anyone explain why and how much of a difference there would be? I understand the RPMs would be different at 60mph. How does this relate to better pulling on flat ground and up hills? Sorry for these questions, I'm trying to explain this to my wife and show a justification for the spending of the funds. Yes, my wife is the BOSS.

 

E4OD with 235/85-16 tires.

3.55 gears in overdrive at 60 MPH = 1650 RPM
4.10 gears in overdrive at 60 MPH = 1900 RPM
4.30 gears in overdrive at 60 MPH = 1990 RPM
4.56 gears in overdrive at 60 MPH = 2120 RPM
5.13 gears in overdrive at 60 MPH = 2370 RPM
5.30 gears in overdrive at 60 MPH = 2450 RPM

Peak torque may be down low in the RPM scale, but peak HP is up at 3300 RPM.
Yes it may pull the load at the peak torque RPM, but heat will be getting high fast.
So you need to get the RPM's up toward the peak HP RPM to keep the heat down.

12,000 pounds with a large frontal area is a hard load to pull.
You not only have to overcome gravity going up a hill, you are also pulling a sailboat with the sail up.

That takes twice the HP it takes to pull a heavy but short load like I usually pull.
The excavator/trailer I pull a good bit is heavier, but the cab is like a phone booth, it don't catch much wind.

Swapping axles is not that hard to do.
With air tools, a Saturday afternoon would be plenty of time.

Unhook E brake cables.
Unhook brake line,
Unbolt driveshaft.
Unbolt U bolts.
Roll axle out.

Roll new axle in.
Bolt axle up using new U bolts over springs.
Hook up E brake cables.
Hook up brake line and bleed brakes.
Bolt driveshaft back up and go for a drive.

 

Thanks for all the info on the different ratios that was great. I have been pushing back and forth on weather its worth making the switch. I'm worried I will see very little benefit from the money spent.

 

Have you tried to lock out overdrive? That will bring your cruise RPM up to 2324 RPM @ 60 MPH. Your torque converter should still lock up and thats a pretty good RPM for towing. It will not harm your truck or transmission and transmission, EGT as well as engine temperatures will be lower. I agree 1650 is way too low for that kind of weight.

The example I have going from 4.10s to 3.08 was before I turbocharged the truck.

10% hill, foot on the floor, the thing would do 46 MPH in 3rd gear with 4.10s. After the swap it did exactly the same speed but in 2nd gear. Why? because your rear axle ratio doesn't matter compared to the final drive ratio. After the swap, I had slightly greater gearing with the 3.08s in 2nd gear than with 4.10s in 3rd. At 46 MPH, 2nd gear would have given plenty of gearing, but the RPMs are beyond the range of the truck.

For getting a load moving from 0MPH, the low gearing will help a lot, but once you are rolling at 60 MPH, it will not make any difference because thats a horsepower limitation, not a rear axle torque limitation. You can only move a load uphill so fast before you run out of power and that assumes ideal gearing.

 

I think that 4:10's and taller are limited slip as well, if that is any advantage to you.

 

I currently lock out the OD with the trailer. I go down the road at about 55 - 60 mph. "IF" I can get her up to 60mph it tows better, there seems to be a sweet spot at that range (3rd gear). My second gear seems to be too high, pushing 50mph or so before shifting to 3rd. So when I hit a hill it drops to 2nd. The problem is there is no way I will get up the hill at that speed (not that I expect to) so it starts dropping and when I get to 35 or 40mph the rpms are low and then it cannot pull the hill with the rpms that low so it shifts to first and I pull the hill in first. My speedometer is off; I think it reads about 3-4 mph high. The numbers I gave are what the speedometer reads.

 

How steep are these hills? Are we talking more than 5% here? Looking in the operators manual for my 86, the trailer tow ratings assume a frontal cross section of the trailer that is not greater than that of the truck (not sure if the same rule applies to your model year). I can't help but wonder if you are towing a 12000lb trailer that also has a large frontal cross section than your problem is more related to horsepower than gearing.

Although having said that, it sounds like the gear spread is getting you caught between gears and causing a bog down situation in your cruise speed. In which case, a gear swap will move those "dead zones" somewhere else in the speed range While favoring the 55-60 MPH speed zone. These engines do have decent low end torque, but when it comes to moving lots of weight, you need to wind them up - or turbocharge (or both in some cases).

With 4.10s, my truck would hover around 3000 RPM @ 60 MPH before I tossed the gears. You will see slightly lower RPMs thanks to the locking torque converter however. My calculations turn out 2500 RPM @ 55 MPH and 2675 RPM @ 60 with 4.10 gears and OD locked out (assuming 235/86/16 tires). That should allow you to have more RPM and Hp at your cruise speed. 2500 is not a bad RPM to be at compared to 2150 (@55) considering the load you are moving.

Am I close, Dave? I'm still running my numbers manually.

 

2675 RPM in third gear would be 60 MPH in that setup with 4.10 gears Dave.

What I am looking at is say 3000 RPM with 4.10 gears would work like this.
1st gear = 24.9 MPH
2nd gear = 43.8 MPH
3rd gear = 67.4 MPH
4th gear = 95.0 MPH

So when you are loaded at 60 or less you have 2.5 usable gears, and the shift points are going to drop you down below your optimum RPM for power every time you shift.

If this was a dailey driver and an infrequent tow rig, then 4.10 gears would still leave decent MPG's and somewhat better towing ability.

But if the main use is a tow rig and it is an infrequent dailey driver, a lower gear set would give you more gears to play with, a lower speed shift point and a better torque multiplication factor to recover from the RPM drop when you shift gears.

Right now with the E4OD and 3.55 gears, if you max out the RPM's at 3300 RPM, you are going 120.7 MPH.
Great for MPG's, but a total waste towing a load.
Shift points look like this if you shift at 3000 RPM.
1st gear = 28.7 MPH
2nd gear = 50.6 MPH
3rd gear = 77.9 MPH
4th gear = 109.7 MPH

So even if you lock out overdrive, the best you can hit a hill at 70 MPH is 2700 RPM in third gear.

Take the 5.30 axle ratio, same 3300 RPM and now the top speed is 80.8 MPH.
So now you have shift points looking like this if you shift at 3000 RPM.
1st gear = 19.2 MPH
2nd gear = 33.8 MPH
3rd gear = 52.2 MPH
4th gear = 73.5 MPH

And the same hill at 70 MPH you are hitting at 2860 RPM in overdrive.

Not going to be great on MPG running empty, but much stronger on towing with little or no drop in MPG.
And you have three full gears to drop on steeper hills.
The shift points have also been lowered to the point that is will be easier for the engine to recover from the RPM drop when you do shift gears since the speed difference will make the RPM drop less between gears.

Find a used turbo in decent shape, throw that on the engine and suddenly you have a very decent tow rig.

If the 5.30 axle is cheap enough, swap the gears into your housing, then you have the gears and the wheels are still the same.

If you swap your old gears into the new housing, you could even sell it and make back part of your investment.

 

If you lived closer I"d swap you rearend for rearend. I have a 4.10 rearend I"d gladly swap but I live in Georgia. To far to drive to swap.

 

dyoungen check your pm

 

the other thing worth mentioning is making sure you understand how gears actually work when it comes to torque multiplication....
Unfortunatly I dont know the ratio's off the top of my head for your tranny, but based on your statment of needing to grab first to pull a hill, and daves calculation above I would put money on you being able to do the same grade in 3rd.

You mentioned being worried about the cost vs benefit, one thing I always do is make a chart with the gears I am considering, what there cruise rpm/speed would be, what there max power rpm/speed would be, and what the available power at each of those actually is. Its not really this simple, but you already know that you need x amount of power (1st gear ratio x 3.55 x engine output) to keep the load moving, so what gear ratio will give you that at a speed closer to what you desire...you also need to factor in wind load etc, but done right you will have an idea of what to expect