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Ford 9 Inch Posi Differential 3rd Member
Ford 9 Inch Posi Differential 3rd Member

Ford 9 Inch Posi Differential 3rd Member

Ford 9", Limited Slip Differential Type, 1310 Yoke U-Joint Series, Standard Ring Gear Weight

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Ford 9 Inch Posi Differential 3rd Member
Ford 9 Inch Posi Differential 3rd Member
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Part # 91049345
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  • Get FREE shipping when your order includes this item and exceeds $99! Ground shipping only in the contiguous US.
  • This item 91049345 is made to order. It will be shipped from our warehouse when it is produced.


Differential Type:
Limited Slip
Housing Material:
Yoke U-Joint Series:
Yoke Width:
U-Joint Cap Size:
Ring Gear Weight:
78.55 lbs.
Sold in Quantity:
Gear Material:


If you’re looking for a complete third member for your Ford 9-inch rear end housing, but want the added performance of a limited slip differential, Speedway Motors now offers you a 9" Ford street 3rd member for your street rod, muscle car or truck. We start with a new reinforced Speedway motors carrier housing and then install bearings, seals, a heavy duty "Daytona" pinion support, a 1310-series yoke, and your choice of ring-and-pinion ratios. The 1310-series yoke is the correct size for many Ford applications with cups 1-1/16 inch in outside diameter and a span of 3-7/32 inch across.

Coupling this bulletproof foundation with our clutch style posi-traction differential provides a proven combination and a welcome alternative to locker & spool differentials which are often overkill and more expensive than the common street car requires.  Based off of the original limited slip designs of the OEMs, these differential units provide the added benefits of millions of miles and decades of proven reliability. Speedway has taken this engineering to the next step in performance with increased clutch pressure and holding power, suiting it well for heavy duty street car applications.

  • Clutch style, spider gear differential = proven reliability
  • Forged steel case
  • Heat treated spider gears
  • Quiet operation, no clicking when disengaging for corners
  • Spring loaded clutch pack with improved grip over OEM designs
  • Proven reliability and economical design
  • Ideal for street tires and medium horsepower applications

This differential has performed well in our Week to Wicked 1952 Chevy Truck, handling the job of transferring a 430 HP GM Performance LS3 to the ground. Speedway Motors continues to bring quality products at an affordable price to keep your project on the road and the race track.

Racing applications with 10.5” tires, drag radials or slicks are better suited for the more expensive locker and Powertrax style carrier designs.

All third members are assembled by our team of professionals and are delivered to you in a handy plastic carrying case, for an overall value that can’t be beat.

Available in your choice of 3.00, 3.25, 3.50, 3.70, 3.89, 4.11 or 4.56 gear ratio in both 28 and 31 spline. 

*Note-When selecting ratio, be sure you are also selecting the correct spline.

3rd Member Installation Instructions (PDF)



Gear lube recommendations : 

91044090 - For street and every day driving under normal conditions

91044140 - For extreme duty, towing or very hot climates



No warranty is offered or made for durability or specific performance. No warranty is offered for commercial, off road, street performance, or racing use.


  • Differential Type:Limited Slip
  • Housing Material:Cast-Iron
  • Axle Splines:Select Spline/Ratio to see
  • Gear Ratio:Select Spline/Ratio to see
  • Yoke U-Joint Series:1310
  • Yoke Width:3-7/32"
  • U-Joint Cap Size:1-1/16"
  • Ring Gear Weight:Standard
  • Weight:78.55 lbs
  • MFG. Part #:Select Spline/Ratio to see
  • Sold in Quantity:Each
  • Gear Material:Steel


As featured on Classic Truck’s Week to Wicked. Watch the transformation here!

Some parts are not legal for use in California or other states with similar laws/regulations

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