Hello, I recently found out I have a fully open diff in the rear of my 1974 Ford F250, it has a 390 FE and has the 8 lug bolt pattern. I was just wondering if it's a simple answer to what axles do I have and what a diff is gonna run me and what's the best limited slip. I thought it'd be easier to ask and maybe someone knows off the top of their head rather than research for hours and get nothing. I wanna know if I have a Dana, Ford 9 inch, or 8.8, I'm clueless and want to know what diff to buy. Thanks

 

Well...we can eliminate 2 right off the bat.....If it's an 8 lug it ISN'T a 9 inch or an 8.8.....Probably a Dana 60 but without pics......

 

74 F250...='s 3/4 ton with 8 lug nuts, I am pretty sure it is a Dana 60. ID is by being able to remove the rear cover by removing some bolts. Also ck the bottom corner webbing to have a 60 cast in it. Also ck for the axle tag that is usually bolted to the side of the carrier with 2 of the rear cover bolts.

Ford 9" is a F100 F150 1/2 ton truck 5 lug nuts,. And does not have a removable rear cover. You have to pull the front "3rd" member to get to its gears.

8.8 is a newer axle under the Explorer SUV I do believe.

https://www.ringpinion.com/

https://www.yukongear.com/

 

My $.02

Pull the diff cover and get the numbers off your ring gear. Plain and simple.

Doing this will kill all the birds with 1 stone. First you will know your gear ratio. Second, You will know what axle you have. Third, you will know the condition of the lube to know if water has been making it by the seals. Fourth, you will know the condition of the gears and bearings.

I was recently fooled by the axle code AND the tag under the cover bolts. They both said 3.54 gears so I ordered 4.10s. When I opened her up to change them, to my surprise I already had 4.10 installed. Also, shipping is high on heavy parts and you can save money by having all the stuff you need shipped in 1 box.

Knowing the condition of all assosiated parts when starting a job on these ~40 yr old rigs can save a lot of head aches and added down time.

 

It is a D60 unless someone did a custom swap with another axle.

The issue you may run into is that the early years of these 73-79 trucks had axles with something like only 10 splines on them. I have yet to see an aftermarket locker or limited slip accommodate that spline count. You may have to get new axles as well.

If you do not know or want to mess around with setting up gears that is going to cost you money as well. You can very easily be $1000 plus into this operation.

IMO this is a wasted effort, as the extra traction you gain is minimal unless you are building a hot rod and need to keep a tire from spinning when romping on it. But, it is your truck and your money.

 

On the 1976 F-250 the tag looked like this:

 

Ha rd to read with such a small picture but looks like maybe 3.07 gears? I had no idea they put anything other than 3.50 or 4.10 ratio in 3/4 tons.

Like others said, don't trust the tag. Here is a very easy way to determine your gear ratio. Put it in neutral and jack one tire off the ground. Move it to where the yoke of the pinion is easily clocked like one u-joint cap being straight up at 12 o'clock. Turn the tire exactly 1 revolution. How far the pinion yoke turned x2 is your gear ratio.

So 1.75 revolutions of the yoke would be 3.50 gear. Just a tad over 2 revolutions, 4.10s. 3.07s would be just a hair past 1.5 revolutions.

 

Yup, starting in '76 you could get a 3.07 (axle code 22) or a 3.31 (axle code 23) ratio in a Dana 60, actually it was the D61 version.

 

On the limited slip rear... I kinda like having the LS rear. It does help keep the truck moving when it is slick... especially with 2 wd. I ran one on a 3/4 ton back in the day. Is it worth swapping? Your choice.

I have worked with Moser axle and "Randy's Ring and Pinion" on other projects and was well satisfied... though never on a D60.

Pulling the axle shafts on these is easy. No need to jack the truck. Remove the retaining bolts at the hub and give the end of the axle a good hit with a hammer. It will bounce loose and you can pull it right out and check splines. Expect a little oil to come out also. A new gasket for re-install is available at NAPA. With good cleanup first, black RTV works also.

 

Great info here. https://www.ford-trucks.com/forums/1...erentials.html

 

You're right; I should clean & paint that before it disappears completely. It does say 3.07. That was the "tallest" ratio for that axle according to the books, and I believe that you had to get the auto trans to have it. It does help some with MPG on that 460/C6 combination.