300F Differential

Here are some pictures of a 300F differential. For what it's worth, this piece
matches the microfilm decoding ( as per Gil Cunningham ) for this
particular car - open rear, 3:31 ratio. The case number on this unit is 1634985 .

First pictures show the rear diff. after cleaning in gasoline only.

Please note the factory paint marks still visible.
Harder to see is the red paint daub right by the filler tube.

Now we're going to paint the sucker. I have no way of finding out the exact
SHADE and COLOR of the paint, so I am doing the best I can based on what I see!

Here's what I come up with!


Harder yet to see is the 3:31 stamping on the housing itself! Wasn't aware they did that!
Picture taken before I applied paint over it, but you can see where it's at - right under the filler plug.

For comparison purposes, please note picture of 300G rear (courtesy Andy Mikonis ); this is an unrestored, less than 100 mile car. Please also note the chalk marks on the housing!

Also, John Roth has this to say ( and picture to boot! ):
"This is what I have done to duplicate what I found upon cleaning my "F" Sure-Grip.
There was nothing on the other side."

And, yet another 300F ... this one's Tony Rinaldi's. Very well preserved.
First a view from the left. Notice the little white mark. I'd never seen one of those before!

Here's a dead-on view. Notice how much paint was applied
at the back, and how far it ran down!

Last view from the right - this one's pretty colorful! Notice red daub by fill plug.

And finally the 3:31 stamping.

The following information was researched by Greg Leggatt, obtained from
Wayne Graefen, and pertains to 1957, It could apply to later years:


Steel die-stamped with axle ratio and "S" for limited slip differential (if so equipped).
NOTE: Also see 'Inspection Marks' for paint daub this area.


Brush stroke of paint covering flat pad on differential carrier lower right side,
after which gear ratio was stamped in:

  • 2.93: 1 light green
  • 3.15: 1 blue
  • 3.36: 1 pale gray
  • 3.54: 1 dark green
  • 3.73: 1 yellow
  • others not known at this time

    The painting of the gear ratio stamping pad is sometimes not present.
    Daub (1 or 2) of matching paint on differential carrier right side snout. This is always present.
    Spray of pale green paint on forward, bottom, or rear face of left axle housing
    which may have runs toward left flange.
    Place approximately in line with breather / brake fitting.


    Yellow paint daub on companion flange and seal dust cover.
    Probably indicates differential has been tested and
    is ready to install to an axle housing.

    Grease pencil stroke, check, or "X" of yellow placed vertically on axle housing
    welded rear cover starting at top and trailing over high point has been noted on some cars.
    Probably indicates axle assembly has been tested and is ready to install.


    And Greg Leggatt adds:

    Thanks for the photos. The information Wayne and I provided for 57 was based on
    observations after washing / cleaning dozens of axle assemblies. I have very few
    3.31 and later 3.23 examples but they are consistent with your work.
    The paint daub applications on John Roths diff. are very consistent with the
    applications in 57 & 58 but we need many more examples
    to zoom in on the "average" appearance.

    I believe we will find that the front green daub is an inspection mark and
    would usually come forward onto the dust shield & companion flange.
    The white or red / orange bottom colors I believe signify 8 3/4
    non Sure Grip &Sure Grip respectively and yellow daubs on the side
    probably signify the 3.31 ratio. We need other ratios from other cars as examples too.

    Well done John, John and Andy. Hopefully your photos will get others interested.
    We need examples from 58 and later. Don't forget to check
    out the axle housings for marks as well.


    Here's a picture of Dave Clelland's 300G rear ( 3:23):