I have a 1953 F100 and I wanted to know the different between the rearend that is a 3.92 gear ratio and a 3.73 out of a 1956. Could I just use the 3.92 with a 302 out of a 1984 Crown Vic or should I change it to the 3.73? Thanks

 

that depends on how you plan to use the truck. Also depends on what transmission is in the truck also.

 

Truckfarmer
I think youcan ,however your cranking it a little tighter than need be. try for 3.00 effective ratio by using 3.00 gear,overdrive trans. or tire size,or any of the above combination. I think this make better hiway gear.
Can anybody tell me what rearend to use for upgrade? Ford 9"or 8.8 preferred. Many various width's.Measure between both BRK MOUNTING FLANGE My 53 f100 original rear measure's 56.75"
I hope for approx 2.79 to3.00 ratio using 235x75x15 tire,fmx tran,&351w aftermkt 4 barrel setup.
Some rear's I've checked are 3" to wideor 2.5"to narrow ThankS cad @ecr.net caddy 53

 

You can use the stock rearend. The one in my 53 is an old Dana 44. The gears are a little high 3.90-1, but makes for tire spinning fun. The other practical option is get a rearend out of a mid-sixties truck. I don't remember the exact years, but this is supposed to be a bolt in with the correct lug pattern. Then you can select any gear ratio you want, since it is a 9 inch ford, and drop it in. This is the easy solution. You can make anything work if you have a tape measure and some welding skill.


truckfarmer
Charter User
219 post
2. "RE: I don't know what to do about the rear end for my 55 F100!! Help!"
01-Oct-01, 10:31 PM (EST)
a 9" from 57-72 will bolt in to the 53-56's. You will need to modify the u-bolts and plate as the 9" has a larger diameter than the Dana 44. If you can get a long yoke on the rearend you can use the same driveshaft. Like mentioned in an earlier post, then you can pick an appropriate gear ratio for your application. Heck, you can have extras for when you want a highway gear or when you want a tire-smoking posi unit.

 

 

I stuck a 9" in mine out of about a '71 F100. Cheaper and easier to find brakes, gears, parts, etc.

 

The 57-60 F-100 nine inch rear ends will bolt up; you will need to use the plates with lower shock mounts and U bolts from the donor truck. 1961-1972 F-100 nine inch rear ends will also bolt up, and you will need to use the plates and U bolts from . The only fabrication is for the shock brackets; try to get the upper shock mounts from the donor's frame (they are riveted on) and measure the location from the axle bumper centerline hole. Then drill and reattach the upper mounts (three holes per mount) to your frame using grade 5 or 8 hardware. The lower mounts on the new 9 inch axle tube will then take a stock 61-72 shock. Look Ma, no welding!
A lot of these truck rear ends still have too high a ratio (3.50/3.70/4.11) for drivability/highway cruise rpms, but any passenger car drop out third member will swap right in (These early 9 inch third members were all 28 spline, just like the passenger cars). Then sell the deep-geared truck third member to a drag racer with a Mustang- or work a trade for his gears- and you are all set.