Flange to Flange Is it an 8" or 9" ?
Types Of 9" Axle Housings How To Recognize Nine Inch Housing Centers
Types of 9" Axles Where To Find The Nine Inch Rear Axle
What information is needed to order axles? What type of metal is used to manufacture the axle(s)?

 

Why is the Ford rear desired by many building hot rods and race cars?

The 8” and 9” have an extra bearing in the front of the pinion to give it extra support. This third bearing reduces flexing of the pinion under hard acceleration. These rears also utilize the axle bearing to retain the axle, unlike C-clips used in some other rears. If an axle were to break, the C-clip retainer, located in the carrier, can not keep a broken axle in the housing. The drop-out carrier also makes maintenance easier.

YEAR/MODEL  (flange to flange)
46"
50"
52"
54"
56"
57"
58 3/4"
60"
'57-'59 FORD/EDSEL
                
'58-'60 THUNDERBIRD
                
'58-'72 F-100 PICKUP
                
'60-'64 FORD/MERCURY
                
'61-'67 THUNDERBIRD
                
'63-'65 FAIRLANE
                
'63-'69 COMET
                
'63-'69 FALCON
                
'65-'66 MUSTANG
                
'66-'69 FAIRLANE/CYCLONE
                
'66-'77 BRONCO
                
'67-'70 MUSTANG/COUGAR
                
'70-'71 TORINO/CYCLONE
                
'70s LINCOLN TOWN CAR
                
'71-'73 MUSTANG/COUGAR
                
'73-'90 F-100 & F-150 PICKUP
                

 

Is my rear end an 8" Or 9"?

On the 9" shown here, the socket won't fit this position or the bolt on the other side of center. Note the pocket at the bolt location necessary because of the larger pinion support. The easiest way to tell is to try to put a socket on the lower bolts. On the 8" shown here, the socket goes on straight without hitting the case.

Where To Find The Nine Inch Rear Axle
  • 1967-1973 medium and big block Mustangs and Cougars
  • 1966-1971 Fairlanes, Torinos, Montegos, Comets, and other Ford intermediates with big blocks.
  • 1957-1959 V8 Fords and Mercurys
  • 1977-1981 Lincoln Versailles & Trucks

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Types Of Nine Inch Axle Housings
  • 1967-1973 Mustang/Cougar - light duty, thinnest housing material, small axle bearings, 28 and 31 splines.
  • 1957-1968 passenger car and 1/2 ton truck - medium duty, stronger than Mustang type, 28 and 31 splines.
  • Ranchero/Torino - heavy duty thick wall housing, 3.25 inch diameter axle tubes with flat tops.
  • 1969-1977 Galaxies (coils), Lincolns (coils), and late pickups (leaf)- 3.25 inch diameter all the way to the backing plate, coil housings have upper control arm mount

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How To Recognize Nine Inch Housing Centers
  • 1957 - no dimples, flat center band up the center of the rear cover, bottom drain plug.
  • 1958-1959 - two dimples on back of housing, flat center band, some had drain holes.
  • 1960-1967 - two dimples, flat center band, oil level hole in back cover.
  • 1963-1977 Lincoln, LTD, Thunderbirds had 9.375 inch centers, housings were cut away at the gasket surface for ring gear clearance, one curved rib at the front top portion of differential, strong but no gears.

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Types of 9" Axles
  • 28 spline axles cannot be shortened and resplined (they're tapered)
    Some can: 69-73 Mustang and Cougars have a straight 28 spline axle.
  • 72 and earlier 31 spline axles have the ability to be shortened
  • 73 and later 9" (big cars) have a 5-on-5 bolt circle and the axles cannot be
    shortened
  • 67-73 Mustang axles identified by wheel flange:
    oval hole - 28 splines two large holes and counter sunk center - 31 splines

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What information is needed to order axles?

Most stock replacement axles are able to be identified by vehicle application, axle length, and axle spline count. For custom axles, there are two diagrams below that indicate all dimensions needed in order to produce a front and rear or shaft. Simply write down these dimensions and call to order. Custom axles usually take two days to make plus shipping transit time to you.

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What type of metal is used to manufacture the axle(s)?

The most common types of metals used in the manufacturing of axles are:

  • 1040 Steel - Stock choice for many OEM manufactures. (Not Desirable).
  • 1050 Steel - Great for stock replacement axles. Approximately 18% Stronger than 1040 steel.
  • 1541h Steel - Excellent for High Performance Street and race applications.Approximately 22% Stronger than 1040 steel.
  • 4340 Steel - Excellent for Extreme Off-road and some Race applications.Approximately 39% Stronger than 1040 steel.
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