What ratios and service tags were available for the Mustang and Cougar 9-inch locking differential?

Service tags WFD-A (3.50:1), WFD-B (3.91:1), and WFD-C (4.30:1), all with a 9" ring gear. The 427-4V with C6 automatic application was Cougar only.

What torque do the ring gear bolts require?

Torque the ring gear bolts evenly and alternately across the diameter to 65-80 ft.-lbs.

How long should new clutch plates be soaked before installation?

Soak new clutch plates in Ford Hypoid Lubricant (Ford Part No. C6AZ-19580-C) or equivalent for approximately 30 minutes before installation.

What is the bench check torque specification for the locking differential?

With new plates, 100 to 250 ft.-lbs (rotating torque may fluctuate up to 40 ft.-lbs); with original/re-used plates, 40 ft.-lbs minimum.

What lubricant and quantity does the differential require?

Ford Specification ESW-M2C104-A (C6AZ-19580-C), 5 pints, service refilled to the bottom of the filler plug hole.

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1968 Ford 4-Pinion Locking Differential Assembly & Model Usage - Mustang Cougar

Ford 4-pinion locking differential assembly procedure with torque specs, model usage chart and hypoid lube spec

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Service procedure for assembling a Ford 4-pinion locking differential, including the shim template, ring-gear ratios by model, torque specs and the C6AZ-19580-C hypoid lube requirement.

AI caption August 2018 · Photo 466 of 486

This page is from a Ford service publication introducing the "New 4-Pinion Locking Differential" (Traction-Lok). It provides numbered assembly steps 6 through 20 covering installation of shaft lock pins, pre-load springs and plate, insertion of a 0.050 shim pack, stacking of friction and steel clutch plates (soaked 30 minutes in Ford Hypoid Lubricant C6AZ-19580-C), compressing the clutch pack with a locally obtained bolt/washer setup torqued 10-15 ft-lbs, using shim template tool T68P-4946-A with a feeler gauge to select proper shims, pressing the case halves together, torquing ring gear bolts to 65-80 ft-lbs, and performing a bench torque check (100-250 ft-lbs with new plates, 40 ft-lbs minimum with re-used plates). A Model Usage Chart (Figure 2) lists applications: Fairlane and Montego passenger cars with 390-2V/4V and 428-4V C.J. engines (tags WFC-A/B/C, ratios 3.50, 3.91, 4.30:1, 9" ring gear) and Mustang and Cougar with 427-4V (Cougar only, C6 automatic) plus 390 and 428 C.J. (tags WFD-A/B/C, same ratios). Tables also give torque specifications and hypoid lubricant requirements (ESW-M2C104-A spec, 5 pints, filled to bottom of filler plug hole).

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Frequently asked questions

What ratios and service tags were available for the Mustang and Cougar 9-inch locking differential?: Service tags WFD-A (3.50:1), WFD-B (3.91:1), and WFD-C (4.30:1), all with a 9" ring gear. The 427-4V with C6 automatic application was Cougar only.
What torque do the ring gear bolts require?: Torque the ring gear bolts evenly and alternately across the diameter to 65-80 ft.-lbs.
How long should new clutch plates be soaked before installation?: Soak new clutch plates in Ford Hypoid Lubricant (Ford Part No. C6AZ-19580-C) or equivalent for approximately 30 minutes before installation.
What is the bench check torque specification for the locking differential?: With new plates, 100 to 250 ft.-lbs (rotating torque may fluctuate up to 40 ft.-lbs); with original/re-used plates, 40 ft.-lbs minimum.
What lubricant and quantity does the differential require?: Ford Specification ESW-M2C104-A (C6AZ-19580-C), 5 pints, service refilled to the bottom of the filler plug hole.