Axle Identification
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Axle Identification
Hi, I have a '78 F-150, 4 x 2, was a 351 M now a 460. The rear axle is coded 15 J on the door. On the axle it says 3.25. What I need to know is it a 31 spline or is it a 28 spline axle? I am looking to buy a 3.50 locker rear axle and I am going to look at a 31 spline one tomorrow. The guy wants $ 250.00 do you guys think that is a fair price? They seem a little scarce around here. I am in Nebraska.
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From: Pa.
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According to that it is a 3.50, 31 spline axle. But the 15 J on the door says it is a 3.25 axle. I am really confused now.
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From: Pa.
So your running 33" tall tires? Your missing 1 number 2.55 x ??? x 18
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Here's another reference that should help clear things up 31 spline
https://www.ford-trucks.com/forums/1...l#post10398311 Need to be sure you don't run to tall a tire with those gears though
https://www.ford-trucks.com/forums/1...l#post10398311 Need to be sure you don't run to tall a tire with those gears though
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From: Simi Valley, CA
[or WDM BA2 = Ford 9" Rear Axle / 3.50-1 / No Limited Slip / D6TZ-4234-A = 31 spline R/L axleshafts.
7FA = Assembled the 1st week (A) of June (F), 1977 (7).
Warranty Plate AXLE code 15J: 15 = Ford 9" Rear Axle / 3.25-1 / No Limited Slip // J = Power Steering.
Compare the VIN on the registration to the VIN on the Warranty Plate to see if they match.
People replaced damaged left doors with used doors. 99.9% of the time, they failed to install the original Warranty Plate on the replaced door.
If the VIN's do not match, the 15J AXLE code is wrong. If the VIN's do match, the rear axle was swapped.
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From: Stanley, VA
What's confusing me about this is the OP says that the axle tag says 3.25 also, not just the warranty plate (15J). WDM-BA2 does cross to a 3.50 ratio, but why would the same tag show 3.25?
I'm wondering if the tag has been misread and the code is actually WDM-BY2, that would cross to a 3.25 ratio.
Kind of a moot point though. Both axles use parts list #88, so both will have 31 spline axles.
I'm wondering if the tag has been misread and the code is actually WDM-BY2, that would cross to a 3.25 ratio.
Kind of a moot point though. Both axles use parts list #88, so both will have 31 spline axles.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
What's confusing me about this is the OP says that the axle tag says 3.25 also, not just the warranty plate (15J). WDM-BA2 does cross to a 3.50 ratio, but why would the same tag show 3.25?
I'm wondering if the tag has been misread and the code is actually WDM-BY2, that would cross to a 3.25 ratio.
Kind of a moot point though. Both axles use parts list #88, so both will have 31 spline axles.
I'm wondering if the tag has been misread and the code is actually WDM-BY2, that would cross to a 3.25 ratio.
Kind of a moot point though. Both axles use parts list #88, so both will have 31 spline axles.
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Ok, Went to the body shop and checked the door tag against the VIN on the registration. They are the same. Called the guy who sold me the truck. He bought it new, he says he has never worked on the rear end except for brakes. The tires are 255 x 45 x 18 on the rear and 235 x 45 x 18 on the front. Love my truck...... why does my tag on the rear end say 3.25 yet definately says WDM BA 2 on the top line?