Daytona Pinion Support and Yoke

Ford describes the part used to support the rear end pinion gear as the "driving pinion bearing retainer and bearing cup assembly", identified by basic part number 4614. It's more commonly called a "pinion support". The pinion support used on all 1968 - 1970 Ford Mustangs equipped with a 9" ring gear and 31-spline rear axle shafts (which just so happens to include Mustangs equipped with 428 CJ and SCJ engines) is often called the "Daytona" pinion support. The service part number for this support was C3AZ-4614-B (Ford used internal engineering part number C8AW-4659-C for the whole assembly), and it was shared with Ford Fairlanes, Ford Torinos, and Mercury Cougars, Comets, and Montegos of the same vintage. The assembly includes one B7A-4616-A bearing, one TBAA-4616-A bearing, and mounts to a 5" hole in the carrier housing. In the pictures below you can see that the casting is marked with an engineering number of C5AW-4668-C, and there's a visible date code that doesn't include the year in which the part was cast. The examples below are L4 (November 4th) and B14 (February 14th).

Daytona Pinion Support L4 Daytona Pinion Support B14 Daytona Pinion Support Rear View
Daytona Pinion Support, L4 Date Code Daytona Pinion Support, B14 Date Code Daytona Pinion Support, Rear View

The part that joins the pinion gear to the driveshaft is known as a "rear axle universal joint flange assembly" and is identified by basic& part number 4851. It's more commonly called a yoke. The service part number for the yoke used with the Daytona pinion support was C4AZ-4851-A (engineering number C4AW-4851-A). This part went obsolete in October, 1973, and was replaced by a yoke with service part number D2OZ-4851-A (engineering numbers D2OW-4851-A and D2OW-4851-B). The yoke assembly includes a C8SZ-4859-A (engineering number C8HA-4964-D) steel dust shield. It's designed for use with a size 1330 u-joint.

How did these come to be known as "Daytona" parts? Here's the story from from former Ford employee Randy Gillis:

Background from "my" research. This casting was created in '62 as a C2AW numbered part BUT it lacked the larger inner pinion bearing. Both bearings were the same 88048 used in the standard part. This revised casting was a result of the original part cracking under racing conditions. Much of the problem was traced to the "crush sleeve" and Ford racers were told to substitute specific thickness solid spacers (before they were a service part) to stop the problem. But the inner bearings were still failing so Ford engineers went to a larger capacity bearing. The "new" part was made with an XW part number and tested in '63 for the upcoming '64 Daytona 500 using the solid, select fit spacer and a larger inner pinion bearing plus external oil cooling. All Ford entries were advised to use the "new" retainer and it was nicknamed the Daytona. The revised C4AW casting (which had the inner portion of the casting modified to take the 89443 bearing) was used in production high performance differentials and for over-the-counter service. A further revision was made and a change to the C5AW casting number which remained in use on 31-spline axle applications until the end of '70. All of these retainers were made using nodular iron. "Regular" bearing retainers kept their "same size" bearings and crush sleeve and "grey iron" material because of their lighter duty usage.

The Daytona yoke can be identified by it's dimensions and the clear space that's about 3/8" deep just above the splines on the back side that mate with the pinion gear. The yoke for a "standard" bearing retainer has a space that's approximately 3/4" deep. This example is also marked with a daub of yellow paint, and the casting is marked "WF" and "31". According to Randy:

Using a standard yoke with a Daytona retainer results in the pinion gear threads being below the end of the nut instead of protruding above the nut. "Some" industrious fellows have undercut the seating area for the pinion nut to correct the situation. This is usually a .200" deeper cut. There is NO negative effect to doing this modification that I have seen but it is still not a "genuine" Daytona yoke.

Daytona Yoke Daytona Yoke Daytona Yoke
Daytona Yoke and Dust Shield with Yellow Paint Mark "WF" and "31" Marks 3/8" Depth Above Splines

The tables below describe the dimensions of the pinion yoke and the differences between the C4AZ-4851-A yoke and the replacement D2OZ-4851-A yoke using illustrations and data found in the Ford Master Parts catalog:

Daytona Yoke Type 2 Daytona Yoke Type 4
C4AZ-4851-A Pinion Yoke D2OZ-4851-A Pinion Yoke
Service Part Number A B C D F G H J K M Type
C4AZ-4851-A 4 25/32" 2 9/64" 3 5/8" 1 13/16" 1 1/8" 3 5/16" 1 37/64" 1 15/64" 1 9/64" 28 2
D2OZ-4851-A 4 25/32" 2 9/64" 3 5/8" 1 23/64" 1 1/8" 3 5/16" 1 37/64" 1 15/16" 1 9/64" 28 4

Thanks to Brian Conway for the part images used here.