I just bought a 1999 F250 light duty. The previous owner swapped out the stock rear axle with an 8 lug rear end. The rear differential has 12 bolts. It looks like the rear brakes stick out a lot. I dunno. I'm going to try a upload some pics. It's currently in the transmission shop getting the 4r100 automatic transmission rebuilt. I got it knowing the tranny was no good. My question is about the rear axle/differential. How would I know the gearing if I don't have any tabs to tell me? P.S. How can I get a pic on here?:-arrg

 

I've got pics in "My Garage" of my rear axle and rear differential. Please tell me what you think. Is this just a standard 8 lug rear end?

 

I've got an 01 F150 7700 which I think is the same truck. I've got 7 lug wheels, 245/75R16 tires. Mine came with load range D tires when I got it 2 years ago, they've been replaced by load range E tires. My rear end is a 10.25", I think 14 bolts on the cover.

On the VIN tag there is a place that says "axle". What does yours say? I'm not sure if you have 4 wheel drive, but I would think if you did the ratio would be the same at both ends.

 

Hello thanks for the response. My truck is a 4X4. I might have forgot to mention the rear axle in my truck has definitely been swapped some time in the past. It has 12 bolt rear differential with 8 lugs at the rear tires. The previous owner said that they swapped the rear end. But that's all I know. I placed a couple pics in "My Garage". Any way that I can identify exactly the setup I have would be greatly appreciated. Thank you.

 

I have posted pics under my name 1999 Ford F-250. There is 3 pics of my truck. Maybe that would help someone help me in identifying this setup. Thank you

 

If it's 4x4, the rear axle had better be the same as the front....or else.

You can figure out the axle ratioo by counting driveshaft vs. wheel rotations with the rear axle up in the air. It's not hard, you can find the instructions with a Google search.

 

The original axle ratio code should be on the door jamb tag.
If the front has not been changed, the rear 'must'/has be the same ratio for 4wd engagement or do not engage 4wd..
The check involves how many times the drive shaft turns with one turn of the wheels.
For example 4 turns of the drive shaft with one complete turn of the wheels would be 4:10 or close to a stock gear offering for the truck.
There can still be an issue if the ratio is even a little off such as a 4:10 or 4:11.
The small difference is in the physical size of the ring gear diameter if the rear has been replaced with a non stock unit.
That difference is the number of teeth and pinion combination for the size of the gears.
You may even have brake balance issues with a larger brake area in the rear.
Good luck.

 

Thank you for describing how to figure out my rear axle ratio. I should tell everyone that I got a real smoking deal on this truck. I new there were some issues with it. That being said. The front driveshaft was sitting under the rear seat when I got it. I thought maybe they never put it back on after they attempted to do some transmission work. Now I wonder if its off because when they swapped the rear axle maybe there was an issue with different ratios....
Very interesting. Thanks again for the info.

 

Ok. I don't know what type of rear axle setup I have in this truck. As seen in my pics in my gallery. I have a 12 bolt rear differential with 8 lugs at the wheels. What is it? Thank you

 

I will look at mine tomorrow. You say 8 lugs on the rear wheels? From the pictures looks like the fronts are the original 7 lugs.. Hmmmmmm..

John in Rochester NY.

 

Yes my rear axle is 8 lugs. You are correct about the front. They are still stock 7 lug. But as I mentioned the rear has been changed. You can barely see it in the pic of the whole truck. If you zoom in you can make out the lugs. But trust me. I promise you that it's 100% 8 (EIGHT) lugs. Thank you. I'm thinking maybe Sterling 10.5 or 10.25 but I hear that only drum brakes were on the 10.25. And my truck has rear disc brakes.

 

Any way of finding out what vehicle that rear axle came from?

 

I wish I had more information about the where the axle came from and any other thing about it. Unfortunately I do not have any info other than what's in front of me.

 

OK Norm, from my previous posts:

My diff is a 12 bolt (the tranny pan is 14 bolts), and looks like yours, which should make it a 10.25", but, the ends are different. I took a (crappy) pix with my c-phone, when I get time I will take a better picture with my "good" camera.

The two ears that hang down on yours - my axle only has 1 and has the bottom of the shock attached to it.....which leads me to ask are there any shock absorbers back there???

VIN tag codes for axles:
2001 Ford shop manual lists these:
NON-LIMITED SLIP;

18 - 3.08
19 - 3.55
26 - 3.73
27 - 3.31

LIMITED SLIP:

H9 - 3.55
B6 - 3.73

I think the 99 F250LD you have and the 01 F150 7700 I have are essentially the same truck and I THINK they are all Limited Slip.

Now, for the front axle:
- in 2001 they were an 8.8" ring gear axle
- shop manual says "an embossed tag, bolted to the rear face of the RH axle tube contains front axle identification information"

So, if that tag is still there, you might be able to see atleast what the ratio should be and work from there via the methods in the other posts to figure out what the ratio actually is.

I was going to measure the track width but my wife ran off with it before I could. As another poster said, can't identify where it came from. Sorry.

Hope this info helps.

 

Knew I forgot something. The 10.25" can have rear disk brakes. Blown up picture in shop manual shows both drums and disks.