Hello,

I am new to the forum and I have a question about a current project I'm working on.

I have a 52 Ford, f-1 with the original 239 v8 Flathead and 3 speed transmission column shift.
I am going to swap out the engine with a 302, and a c4 transmission. I have found a 9 inch rearend to drop in the truck that came out of a 59 ford f1 to match up with the transmission.

My question is, what gear ratio would I use in the rear end to match the c4 transmission? Could I keep the stock 9 inch rearend from the 59 an not change the gears, providing they are in good shape, or would I need to swap?

I am new to this swapping rearends thing so any help would be greatly appreciated!!

Thank you!

Jon Preston

 

Depending on what diameter tires you use, you want a ratio of not more than 3.25. It isn't likely the '59 rear end has gears that low, probably more like 3.70 or as high as 4.11.

 

Thanks! I appreciate the information!

Jon Preston

 

Hey Guys, i am brand new to to forum and i have a couple of question. first i have a 99 F-150 with 35's and a 3" body lift and i 5 inch RCD suspension. i think that some noise that i have coming from the back are the gears. does anyone know how to tell what you have stock and any recommendations for new gears. i will be moving in a few weeks and will doing a lot more highway driving than now, so i want something that will get up and go but not have that loud whine from the back. any help/suggestions wold be appreciated

 

I have a 289 from 1966 Mustang with a C4 transmission . I am thinking i need a 300 gear for my truck

 

ravert, you might want to post this question in the forum that is the correct year. This is the 48 - 60. While I am sure that someone here could tell you, it would be quicker if you asked with the proper year.

 

Jon: Tire size makes a big difference, but so does what you're planning on using the truck for; if you're looking for burn outs, or larger tires, the stock gears will be fun, if you want more economical you'll probably have to swap them out to around 3.25. It will be faster (top speed), but not quicker (0-30mph). I would suggest swapping in your new power train and then seeing how you like how it's geared. You can do it with math and where RPM's should be at and what not, but you might find your driving style prefers something less logical and more fun, lol.



Ravet:

Mark the tire at 12 o clock, mark the drive shaft too. Put the rear off the ground and the transmission in neutral. Spin the drive shaft 10 times, have someone count how many times the mark at the tire when to 12 o clock again. Divide the number of tire rotations by the number of drive shaft rotations and that's your rear gear ratio. Most accurate way with as little guessing as possible if you want it to the hundredths is to spin the drive shaft 100 times, but at 10 you can figure it by where the mark ends up.

If you spin 10 times and the tire rotates exactly 30 times, you have 3.0. If you spin it 10 times and it rotates 35 times, you have 3.5. The hundredth number can be guessed by where it's at, say 6 o clock, thats half way, so it's 3.55 for this example. Slightly less is 3.54. If you want to be critical and know for sure, spin it 100 times. It's not fun to try to keep count though, lol.

 

Ravet, as new as your truck is, it likely still has a tag on the diff cover that tells you the ratio.

 

Well...first...welcome to the forum to all three of you.

Jon..on the 9" that you have from the 59, see if there is still a metal tag attached under one of the nuts that holds the rear end into the housing. If you have it, clean it up carefully and get the numbers off of that tag.

Albuq is spot on with 3.25:1 ratio for either of your engine trans setup (both John and Jon). I'll caveat that with the notion that there are differences between trucks and what you want to do with it. If you're drag racing, maybe a lower ratio....if you're on the freeway all day, maybe a little higher. The F1's are pretty light, so probably comparible to the Mustangs that the 289/302 C4 combination came out of. It also will depend a lot on the height of the tires that you choose.

Ravert...welcome aboard, but I think you ought to hit up one of the 4x4 forums to find out what is working with the 35's....that is a really tall tire & you may need a relatively low gear ratio to balance that out.

Dan

 

I second looking for the tag. If you find it check out this link.

Ford Rear Axle Assembly Identification - Page 01 - FORDification.com

 

52' Fordnut,

I see you're from KY. What part? Does your truck run now?

 

Thanks guys! I really appreciate all of the help!! I haven't picked up the rearend yet but I have purchase 2.75 gears because for what use I'll be using the truck for is mainly cruising down the interstate, and back and forth to work, not as a daily driver but a recreational vehicle, you know, car shows and such.

Thanks for all the help, I'm sure I'll be back on here at some point for more help!

Also, I'm from the southern part of ky, bout an hour from Knoxville.

Thanks again

Jon Preston

 

I went with 3.00 gears and have pretty much the same application. Originally my rear end came with 2.45 which means my cleveland would redline and 159mph! But for what good on the interstate that would be would kill you in the city. Being in Kentucky I know staying outside Louisville and Lexington its all pretty much like highway.

 

I just now pulled a tag off of the rearend that is currently on the 52 and the tag reads

W 47
12

What would this mean as far as the rearend in the 52? Once again this is the stock rearend on the truck as far as I know.

 

It should be a Dana 41 with 3.73, 3.92, or 4.27 gears. None of which would be highway suitable. Are you around Corbin Kentucky? I am Bowling Green.

*Found this old thread here, which seems to confirm what I read on another page.
https://www.ford-trucks.com/forums/8...rear-diff.html