All assemblies are hand-assembled by our trained technicians for an unbeatable combination of quality and value. For Race/Off-Road use only. NOT for Street use., Features precision assembly for the correct backlash, preload, and proper amount of pinion shims to ensure the correct pattern on the ring gear teeth, The nodular iron housing is stronger than OEM “gray” iron and has 4 lbs. of additional reinforcement, Includes a large bearing “Daytona” style pinion bearing supports for strength and reliability, Comes with a new, forged steel 1310-type "Ford short" pinon yoke
Ford 9 In. Racing 3rd Member Assembly 31 Spline Mini Spool 3.70 Ratio Speedway Motors
Ford 9 In. Racing 3rd Member Assembly 31 Spline Mini Spool 3.70 Ratio
Sku # 91048341-370
Mfr. Part # 91048341-370
Condition
New
Brand
Speedway Motors
Sold
Box
Details

Assembled by Professionals

Hand-assembled by trained experts in-house, our Ford 9-inch third members are built from quality components with an exact step-by-step process. We bring this combination of precision assembly and quality components to you at a price that can’t be beat. We trust these third members so much, they’re the go-to choice for our own rides, from the street to the track. 

Tough, Nodular Iron Center Section

Our Ford 9 Inch Nodular Iron Third Member Center Section Carrier starts with a NEW casting with over 4 lbs. of additional material in critical areas. Nodular (ductile) iron is much more resistant to fracturing than OEM “gray” iron. Extra ribbing reinforces the case and rearmost pinion support (pilot bearing). 

Thick, forged steel bearing caps surround the carrier bearings, all securely held in place with precision Grade 8 cap screws. The improvements continue with rugged billet steel adjuster nuts and heavy-duty keepers to ensure your ring gear settings are maintained. All mounting surfaces are precision machined to ensure a consistent, flat surface for a positive gasket seal (no more leaks on your shop floor). An oil fill plug is included. 

Precision Assembled For Proper Ring Gear Teeth Pattern

Getting a proper pattern on the ring gear teeth is crucial. Our time-proven, step-by-step process ensures the correct backlash, preload, and proper amount of pinion shims to ensure the correct pattern on the ring gear teeth. 

To ensure a proper gear pattern, we use a stronger “Daytona” style pinion bearing support to maintain that critical pinion depth setting. Stronger due to its larger bearings, our Daytona pinion support also uses the spacer-and-shim setup to maintain critical pinion depth settings under high load, unlike traditional crush sleeves which often compress further, take out your preload and lead to failure. With solid bearing spacers and the proper shims, we eliminate this problem and make setting preload easy and repeatable during installation, service and gear changes. Since preload is already set, simply torque the pinion nut to 160 ft./lbs. and you’re good to go. The pinion gear is connected to our new, forged steel “Ford short”, 1310-type pinion yoke. 

Note - Speedway Motors Differential 3rd members come with a 1310 Universal Joint (U-Joint) series yoke. No other Yoke size options are available. 

1310 series U-Joint and Bearing Cap Reatainers Not Included - 1310 Series U-Joint Options

Gear units are built from long wearing, tough 8620 cold-rolled steel. We offer lightened gear assemblies from 5.29:1 to 7.33:1, select the "L" option (example: 529L) from the gear ratio selection. 

Premium Mini Spool

Our mini spool assemblies have premium, forged 8620 steel 31-spline mini spools, with a chromoly cross pin, and are built with a larger diameter for greater durability. We offer gearing from 3.50:1 to 7.33:1. Mini spools are a great option for restricted class racing and saving money. 

Proven Reliability

We race what we sell. Our third member units are the go-to choice for our own rides and racecars and we have built these units to last with high quality hardware and components. Tapered steel roller bearings minimize friction, better handle thrust loads and increase load carrying capacity. The ring gears are assembled with Grade 9 bolts with a tensile strength of 180,000 psi, a 15% increase over Grade 8 hardware.  Heavy duty Grade 8 carrier cap bolts, a lock-style pinion nut with pre-applied Loctite and high-quality grade 5 pinion support bolts make our third member near-bulletproof. 

Units include a Viton® pinion seal providing long lasting oil and chemical resistance. This seal retains elasticity up to 399°F (204°C) and intermittently up to 600°F (316°C) This high temp seal helps eliminate pinion leaks, reduces maintenance and keeps the third member properly lubricated. A carrier-to-housing gasket is available separately. 

Our hand-assembled Ford 9 inch third member assemblies are made-to-order. We keep a supply of the most popular gears in stock, with most units built within 2-3 days. Our third-member units are shipped in a durable, reusable poly storage case, perfect for keeping multiple gear sets stored and ready for the track.

Features

  • Hand-assembled by our trained technicians for an unbeatable combination of quality and value
  • Track-tested durability in our own cars – we race what we sell
  • Precision assembly for the correct backlash, preload, and proper amount of pinion shims to ensure the correct pattern on the ring gear teeth 
  • Nodular iron housing is stronger than OEM “gray” iron and has 4 lbs of additional reinforcement
  • Large bearing “Daytona” style pinion bearing supports for strength and reliability
  • New, forged steel 1310-type "Ford short" pinon yoke
  • Spacer and shim setup is maintains critical pinion depth settings and easier to service than traditional crush sleeves
  • Gear units built of long-wearing 8620 cold-rolled steel, lightened gear options available
  • Ring gears assembled with Grade 9 hardware, 15% stronger in tensile strength than Grade 8
  • 31-spline premium mini spool
  • New chromoly cross pin
  • Viton® pinion seal, resistant to chemicals and high temperatures
  • Grade 8 Carrier cap bolts
  • Lock-style pinion nut with pre-applied Loctite®
  • Grade 5 pinion support bolts
  • Includes form fitted, reusable red poly storage case
Specs
Differential Type
Mini Spool
Housing Material
Cast-Iron
Gear Ratio
3.70:1
Axle Splines
31
Yoke U-Joint Series
1310
Spool Weight
Standard
Ring Gear Weight
Standard
Weight
83.25 lbs.
MFG. Part #
91048341-370
Sold in Quantity
Each
Gear Material
Steel
Yoke Included
Yes
Ring and Pinion Included
Yes
Reviews

Yes

Rated
Product Rating
by Speed racer on July 23, 2026

Summary: Dirt. Track racecar

Yes, I recommend this product.

Best company to deal with

Rated
Product Rating
by Hot rod on December 17, 2025

Summary: Installed in my Willys coupe, LQ4 , 4l80e Speedway provide almost every part of the build. Great Company.

Yes, I recommend this product.

I'll buy again if it works alright

Rated
Product Rating
by Ralphy on October 29, 2025

Summary: Finishing up car

Yes, I recommend this product.

Good quality so far

Rated
Product Rating
by james on August 20, 2025

Summary: I have about 6 nights on these gears and so far they are working great. they feel like they have less drag that my other sets of gears as well.

Yes, I recommend this product.

Great gears @ great prices

Rated
Product Rating
by 2FingerRacing on August 11, 2025

Summary: This is my third gear that I've purchased through Speedway. I won't take chances buying used third members & hoping they last, when I know I can get a brand new gear for this price. Had a local shop make me a gear using my chunk and new ring & pinion - it was more $$ than buying a brand new gear from Speedway. #neveragain

Yes, I recommend this product.

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Tech Support
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About
Speedway Motors is America’s Oldest Speed Shop® and has been a trusted source for specialty rodding and racing products and friendly expert advice for more than 74 years. Founded in 1952 by “Speedy” Bill Smith – a racer and street rodder himself – Speedway has grown from a one-man operation to become the world’s largest manufacturer, distributor and retailer of street rod and racing products. Our industry-leading fast delivery is the result of same-day shipping from our state-of-the-art, centrally located 500,000 sq. ft. headquarters. Speedway’s size offers customers unmatched product selection and low pricing, while our excellent technical support and customer service have made us a recognized leader in the rodding and racing industries.