Everything You Need To Know About Quick Change Axles

How a Quick Change Rear Axle can Transform How Your Rod Looks With Winter Performance

By Chris Shelton   –   Photography by Precision Hot Rods & Winters Performance

Ah, there’s nothing quite like the look (or whirr) of a quick change rear axle. Inspired by circle track racers who needed to fine-tune their gearing to suit course conditions, the venerable quick change rear axle has made its way under just about everything, including land speed cars, sports cars, dragsters, Modifieds, and even drift cars.

02 Winters Performance shipped a 56 inch axle complete with limited slip and axle shafts
Winters Performance shipped a 56-inch axle complete with limited slip and axle shafts. For the mockup, Chico Caraballo protected the centersection’s delicate polished finish with masking tape.

What’s A Quick Change Rear End?

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A quick change rear axle is basically a conventional axle with a gear case modified or designed to use a pair of spur gears. In a conventional axle, the driveshaft and pinion rotate at a 1:1 ratio. In other words, the pinion rotates at the same rate as the driveshaft. But the spur gears in a quick change rear axle alter the ratio between the driveshaft and pinion. Depending on how it’s oriented, a spur-gear set can spin the pinion faster or slower than the driveshaft to alter the axle’s final drive, or its total gear ratio. That’s a big deal when trying to tune an engine to operate within its peak powerband on a racetrack.

03 A frame built for a quick change axle doesn t necessarily differ from any other frame
A frame built for a quick change axle doesn’t necessarily differ from any other frame, but the spur-gear housing does require some concessions that Danny Tesar and Caraballo made for this application.

Benefits Of A Quick Change Rear End?

But one could make the case that nearly as many quick change axles live under cars that will never see a checkered flag. After all, few things convey a sense of performance more than real race car parts. But quick change axles offer real utility to even road-going vehicles. It takes a few minutes to make the change, but there’s a gear ratio for everything from long-haul treks to events and blasts around town once you’re there within one set of properly chosen spur gears.

04 nothing says nostalgia more than a quick change peeking out from under a Model A spring
To accommodate the spur-gear case, they swapped the flatter Deuce-style crossmember and spring for one of their Model A crossmembers and a Posies spring. Other options exist, like coils, coilovers, air springs, or even torsion bars. But nothing says nostalgia more than a quick-change peeking out from under a Model A spring.

Due to Precision Hot Rods in Macedonia, Ohio, we can add another street-driven example to that list. Danny Tesar and Chico Caraballo recently built a Deuce chassis specifically to house a complete Winters Performance quick change axle.

05 They located the axle with a Roadster Supply Company forged end ladder bar kit
They located the axle with a Roadster Supply Company forged-end ladder bar kit, splitting the axle brackets since the axle ends prevent them from sliding on. They pointed the pinion 3 degrees up from level in anticipation of the tailshaft pointing down the equal amount. They also threaded the clevises halfway in to offer the most adjustment potential.

Factory Gear Housing Vs Aftermarket Gear Housing

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Though conceived as a gear case that used existing Ford or Dana components, the quick change gear housing evolved into a complete axle made of entirely new parts thanks to Winters Performance. Building an axle from all-new components pays dividends greater than eliminating the need to hunt down and restore vintage parts. For one thing, building from scratch opens the door to make the axles stronger and perform better.

06 Tesar then installed the spring hangers by the same method he used on the ladder bar brackets
Tesar then installed the spring hangers by the same method he used on the ladder bar brackets. Rather than position the brackets individually, he made this fixture that holds them parallel and at the correct distance apart.

The Evolution Of The Quick Change Axle

To understand why is to know the origins of the heart of the quick change axle: its gear case. The most popular design in the hot rod world evolved from the banjo-style axle used in ’35-48 Fords. Squint just right at a bare quick change housing and you’ll likely see that—design-wise anyway—a quick change housing is basically a Ford banjo flipped backward and amended with a quill-shaft boss and a spur-gear housing. In fact, the earliest examples of quick change housings are nothing more than Ford banjos that users flipped backward and modified with some castings, a quill shaft, and spur gears.

07 Once they got everything in place Tesar and Caraballo reattached the remainder of the brackets and welded everything together
Once they got everything in place, Tesar and Caraballo reattached the remainder of the brackets and welded everything together (note the bead across the hanger bracket). He also installed the Roadster Supply Co. lower shock mounts at the same time.

The Problem With Ford Banjo Axle-Shaft

While convenient, Ford banjo parts have a few issues, mostly axle-shaft related. Specifically, those shafts break under duress. Over the years various builders adapted Ford 9 inch rear end bearing housings to Ford axle tubes, opening the door to stronger semi-float shafts. But that still required finding obsolete parts if you wanted to run Ford-style tapered axle bells. Winters Performance took things another step further by making the bells from scratch with the 9-inch bearing housings in place and including semi-float shafts in a complete assembly. Then the company took it upon itself to build a dedicated limited-slip gear carrier, conferring the benefit of equal torque to both drive wheels to the design. According to Winters Performance Curt Iseli, the result is an axle assembly capable of handling 600 hp in an application that can achieve traction sufficient to hook up.

08 Spring spreaders make quick work of the job but this spring s reversed eyes prohibit their use
Spreading a transverse leaf spring isn’t the easiest. Spring spreaders make quick work of the job, but this spring’s reversed eyes prohibit their use.

Flexibility Of Axle Combinations

Winters Performance offers the axles in near countless combinations. The standard bell-style axles measure 56 inches wide. But because the tubes straighten out, axles with Ford-style housings can go as narrow as 48 inches and as wide as 60 inches. The ribbed-style axle housings can go narrow enough for Pro Street applications and nearly indefinitely wide. Complete axle assemblies include a limited-slip carrier and 31-spline axles, but Winters Performance sells the components individually if you’re inclined to run a Ford gear carrier.

09 Tesar and Caraballo disassembled the spring and installed it on the shackles
The main plate (leaf), however, can be wrestled into place almost easily. Tesar and Caraballo disassembled the spring and installed it on the shackles.

Ring and Pinion Options

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Three ring-and-pinion options and 36 spur-gear options offer a fine degree of resolution across a whopping range from 1.80:1 to 11.33:1. Other options include (but aren’t limited to) numerous gear cover designs, multiple finishes, including polished and Teflon coated, and a variety of brake packages.

10 if it wasn t obvious why Model A springs go with quick changes like peas and carrots
Then they installed the remainder of the spring plates. This perspective should remove all doubt if it wasn’t obvious why Model A springs go with quick-changes like peas and carrots. A stock Deuce spring would go right through the spur-gear housing.

Conventional Axle Vs Quick Change Axle

While different internally, a quick change axle assembly mounts much like any other axle, with only one potential exception: spur-gear housing clearance. Though it affects primarily ’32-48 Fords like the subject of this installation, Larry and Tesar show us how they prevailed in what’s probably the most time-honored method. The housings can also interfere with fuel tanks—the Ford Deuce is a known example—but remedies run the gamut from notching the tank to flat-out relocating it as Larry and Caraballo did.

11 Though not necessary for a quick change installation Precision Hot Rods spring clamp
Though not necessary for a quick-change installation, Precision Hot Rods’ spring clamp tidies up the crossmember by eliminating the U-bolts and cumbersome clamps.

The Drawbacks Of A Quick Change Axle

But beyond that, installing a quick change axle presents few significant issues (even the cost of a complete Winters quick change remains competitive with a new, similarly equipped 9-inch). In fact, the only thing keeping a quick change axle from under your hot rod is, well … you. MR

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How to Calculate Ratios Axle’s Final Drive

Options are everything but they don’t matter if you don’t know which ones you need. Here’s the formula for calculating the axle’s final drive, or the product of the ring-and-pinion and spur gears.

(Driven-Gear Teeth/Drive-Gear Teeth) x Ring-and-Pinion Ratio = Final Drive.

This is how a 3.78 ring-and-pinion with a #4 (22/26) spur-gear set works out with the 22-tooth gear as driven (upper) and the 26-tooth gear as the drive (lower):

(22/26) x 3.78 = 3.20:1

In this orientation, the spur gears calculate to 0.846:1, or roughly a 15 percent overdrive. That makes an axle with a 3.78:1 ring-and-pinion behave as if it had a 3.20:1 ring-and-pinion. That’s great for reducing engine speeds on the highway.

Now flip that spur-gear set with the 26-tooth gear as the driven (upper) and the 22-tooth gear as the drive (lower):

(26/22) X 3.78 = 4.30

In this orientation, the spur gears calculate to 1.182:1, or roughly an 18 percent underdrive. That makes our axle with the 3.78:1 ring-and-pinion behave as if it had a 4.30:1 ring-and-pinion. That’s great for increasing torque for those stoplight blasts.

Sources
Posies Rods and Customs
(717) 566-3340
posiesrodsandcustoms.com

Precision Hot Rods and Fabrication
(330) 908-0234
precisionhotrodsandfab.com

Roadster Supply Company
(714) 583-4118
roadstersupply.com 

Winters Performance Products
(717) 764-9844
wintersperformance.com

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