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Replacing Rear Yoke - 1978 F150 4X4

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Old 04-21-2018, 04:12 PM
Charles Howard
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Question Replacing Rear Yoke - 1978 F150 4X4

Recently my rear axle dumped a bit of fluid from around the yoke so I it's time to replace that seal, gasket, and the yoke itself since mine looks like it's been welded on. Another symptom is when I let off the gas at highway speeds I get a bit of a vibration and a vibration that starts at around 80 mph.

The question is: what yoke do I need?

There are three different yokes available on Bronco Graveyard for a 1978 F150:

Ford 9 Pinion Yoke 1310 Flange, 3.5 (Short yoke for Ford 9" with 28 spline pinion and a 1310 U/Joint size, 3.219" snap ring span, 1.062" cap diameter)
https://shop.broncograveyard.com/For...uctinfo/22280/

Ford 9 Pinion Yoke 1330 Flange, 3 7/8 (uses 1 1/8" Cap Size U-joint)
https://shop.broncograveyard.com/For...uctinfo/22282/

Ford 9 Flange, 1350 Series
https://shop.broncograveyard.com/For...uctinfo/22284/


Additionally, what all do I need to do this job right?

My list so far:

- Pinion seal
- Crush-sleeve eliminator kit (https://shop.broncograveyard.com/9-I...uatinfo/22293/)
- Pinion nut
- RTV


Here are some pictures I was able to take (can't take the yoke off and measure correctly in my apartment parking lot so I was hoping this would suffice):



The yoke




Measurement of the rear drive-shaft cap (1.0735")




Measurement of the yoke cap (1.0465")
 
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Old 04-21-2018, 05:14 PM
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2WD/4WD makes no difference.

With or without Limited Slip? What is the spline count of the axle shafts, 28 or 31?

Is the rear axle ID tag still present?

This is not a yoke, it's the companion flange on the rear axle. See 4851 in pic:

 
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Old 04-22-2018, 02:56 PM
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I'm not sure of the spline count but I do know it is an open differential. The only tag I was able to find was this one that reads "7JC" on the top and "390B" on the bottom line:

 
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Old 04-22-2018, 04:53 PM
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Originally Posted by Charles Howard View Post
I'm not sure of the spline count but I do know it is an open differential. The AXLE ID tag I was able to find was this one that reads "7JC" on the top and "390B" on the bottom line:
What I need and what you missed is: On the far left side of the AXLE ID tag (underneath the road grime) is the AXLE code, will be similar to WDM-AA

7JC = Rear axle assembled the 3rd week (C) of September (J), 1977 (7).

390B is the assembly plant code.
 
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Old 04-23-2018, 09:42 AM
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Originally Posted by NumberDummy View Post
What I need and what you missed is: On the far left side of the AXLE ID tag (underneath the road grime) is the AXLE code, will be similar to WDM-AA

7JC = Rear axle assembled the 3rd week (C) of September (J), 1977 (7).

390B is the assembly plant code.
Sorry about that, got it this time with some PB Blaster:

 
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Old 04-23-2018, 09:55 AM
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Originally Posted by NumberDummy View Post
What I need and what you missed is: On the far left side of the AXLE ID tag (underneath the road grime) is the AXLE code, will be similar to WDM-AA

7JC = Rear axle assembled the 3rd week (C) of September (J), 1977 (7).

390B is the assembly plant code.
Wouldn,t J be for October not September?
 
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Old 04-23-2018, 10:31 AM
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Originally Posted by JessyJ View Post
Wouldn't J be for October not September?
No.
A = January, M = December. The letter I is skipped.

Pic in post #5: WDM-BZ = D6TZ-4851-A .. Companion Flange-Use with 1330 sized U-joint / Obsolete ~ 26 available NOS

1976/78 F100/150 with 28 spline axleshafts.

Upper pic: Pictures of 4851 companion flanges and how to measure their specs.

Lower pic: See D6TZ-4851-A .. TYPE #4 .. Column right - 7th entry from the bottom of the page.

Click on the pics twice to enlarge them.



 
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Old 04-23-2018, 06:06 PM
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Make sure your vent tube isn't plugged up.
 
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