Ok so a lot of folks grab a 9" to open up gear ratio options, sooo it is kinda on topic bear with me.

I went to a junk yard and pulled a 9" off a 72 Ford 1/2 ton, and only did a couple quick checks - ratio, and opened up the case to drain fluid thuroughly and check no massive wear or chipping of gears.

I did not check 31 spline versus 28 spline (oooops).

I've subsequently done a ton of research before asking, and can't positively tell without tearing it open again.

The outer hubs have the center chamfer and 2 holes, not the oval slot - I know that rules out a positive 31 spline id, but leaves possibility it could be either 28 or 31 still (from popular 9" guides).

The tag reads:
WDM-AG 2FA
3.00 9 343A

Supposedly according to every 9" site you can cross reference the spline based on this.... my problem, all sites claim this, but nobody posts a chart or lookup or reference.

Reason why I am asking, I am heading to the junkyard to get more T5 stuff and as long as I am there I figure I will poke around for a locker 3.50 - I'm not too lazy to tear it apart, but I am just not thrilled with opening it up given that it is currently a running ,driving truck and it is the workhorse that will be going with to go get parts today. If I don't get a definitive I will tear it open either this weekend or next - so no worries if you just can't help me figure it out.

 

You've got a 31 Spline set up. It is true that some post '71 31-spline axles have the "oval", no 28-Spline axles have the 2 holes that I've ever seen or heard of?

Just to be save, jack up one side of the axle, pull the wheel, brake drum, brake backing plate and brakes (one assembly - 4 bolts) and then slide the axle out and count. Shouldn't take too long at all. I say to jack it up so gear oil loss is minimal... Good luck!

31 Spline:


28 Spline (and some post 1971 31's):


Jim

 

Is a non-locking 9" with 3.00 gears and 28 splines from an F100.

WDM-AG1 would be with 31 splines, but not made until 1973.

 

Not doubting, cause you sound pretty sure, but mind sharing how you figured that out so I can decode in the field (junkyard)? I get the 3.00 versus 3L00 (second line)... but the splines I can't find any guide/chart/database on that.

 

I at least looked smart for a second there, didn't I? lol.
Ford Rear Axle Assembly Identification - Page 01 - FORDification.com

 

and I thought I was the google master - can not believe that didn't come up in all the variations of the search I did....sometimes it just takes a fresh set of eyes.

 

I've known about that site for quite awhile. It does come in handy, though in the early days of FTE there was a rift between the two sites. Hopefully everyone's grown out of it.

 

Just curious, what is the best gearing to use behind a stock flattie? I think the 9" I have is a 3.25. It's out of a '72 F-100 I think, maybe a '71.

 

I think that depends way too much on transmission for a simple answer.... IF my crash box was all synchro and I didn't have to double clutch with that big pause between gear then I would love my 3.00. One lesson I learned is that you keep your final drive ratio (1st gear) above 10:1 - preferably above 10.5:1 to keep from killing the clutch on takeoff.

My thoughts, with a manual - aim for about 11:1 final drive, understand the higher (lower numerically) the gear the higher the top end and possible fuel economy but the worse the accelleration (and at 3.00 I just don't have any acceleration). Drag race guys often times hunt down the 4.11 posi rear end, so I would say "generally regardless of transmission" anything in between a 3.25 and a 4.11 is a good fit - higher than a 4.11 and you have a stump puller with no top end, lower than 3.25 and you have a slow accelerating unit that doesn't save you enough fuel to be worth the road manner.

 

Any one of those rear ends mentioned above will take care of any thing your old truck will toss at it. (within reason)!

 

My F-1 panel has a synchronize 3 speed. I found the 9" on CL a few years back for $75 with all new brakes. Now I just have to get the time to put it in.

 

hmmm... 4 options of 3 speeds that I knew of - one not used after 50 though castings of 3C, 3CS, 3D, and T89 here's my research - the green chart:
https://www.ford-trucks.com/forums/1...l#post11121365

If you have the 2.78 first gear than I wouldn't want to put anything lower than a 3.73 rear in.

Know what your 1st gear is and want to double check your rear end tag before I give you the bad news?

 

Well I'm suppost to have the 4.11 in my 9", but behind the th350 and I have to either change my transmission (to a 700R4) or the gearing as I can't go onto the freeway that well...

 

I have the truck in storage right now and can't get to it. I have another panel truck sitting in my shop that's half cut apart, I'll try to take a look at that one to see what tranny is that one. I have the 9" also in my shop, I'm pretty sure the tag says 325.

 

WDM-AG = Ford 9" Rear Axle / 3.00-1 / non Limited Slip / 3,300 lb. Rear Axle Capacity / Rear Axle Parts List #91: C8TZ-4234-A .. 28 spline axleshaft / C9AZ-4221-A "Slim Line" tapered roller differential bearings (intro'd mid-year 1969).

2FA: Assembled the first week (A) of June (F), 1972 (2) / 343A: 343 = Assembly Plant Code / A = 1st Design (B would be 2nd, C would be 3rd and etc).

IF it had 31 spline axleshafts, the AXLE ID tag number would begin with either WEY or WFF

The ring gear would be 9 3/8" diameter, would have Limited Slip (Traction-Lok) and a 3,600 lb. capacity. The H/D 9" w/a 9 3/8" ring gear was an option for 1968/72 F100's.

> > Info source: 1964/72 Ford Truck Parts Catalog / Text, Section 40.3, Page 2: Differential Carrier & Rear Axle ID Charts. < <

1959/60 Rating Plate; 1961/80 Warranty Plate; 1981 thru today Certification Label: If the AXLE code begins with a letter: Limited Slip / If with a number: No Limited Slip.

NOTE: Ford did not offer Limited Slip w/a 9" until 1968 in F100's. 1959/67: If Limited Slip was ordered, Ford usually installed Dana 44's. Dana 60.2 (1963/66), Dana 60.3 (1966/68) were also optional. These are NOT Dana 60's.

Ford type 3.03 3 speed manual all syncromesh transmission introduced in 1963. Will be found in 1963/83 misc Passenger Cars, 1963/83 F100, 1966/77 Bronco, 1969/87 Econoline, 1975/86 F150.

3.03 Warranty Plate TRANS code: A = 1963/65 / C = 1966/87.