WHAT TO LOOK FOR IN A THIRD MEM­BER

WHAT TO LOOK FOR IN A THIRD MEM­BER

4 Wheel & Off Road - - CONTENTS - Harry Wag­ner EDI­[email protected] BY PHOTOGRAPHY HARRY WAG­NER

The Ford 9-inch con­tin­ues to live a healthy life.

DE­SPITE LAST BE­ING OF­FERED UN­DER A PRO­DUC­TION ve­hi­cle in 1986, the Ford 9-inch con­tin­ues to live a healthy life thanks to its light weight and abun­dant ground clear­ance. Not all 9-inch com­po­nents are equal though when it comes to strength, or price for that mat­ter. To il­lus­trate the bevy of op­tions, we re­cently took a fac­tory third mem­ber and com­pared it to an af­ter­mar­ket third mem­ber from G2 Axle & Gear and a money-is-no-ob­ject third mem­ber from Gear­works. All three were fit­ted with ARB Air Lock­ers, but even the se­lectable lock­ing dif­fer­en­tials are not cre­ated equal.

At the beer bud­get end of the spec­trum, we used a fac­tory 9-inch third mem­ber and the orig­i­nal pin­ion sup­port and 1310 yoke. To that we added 4.88 gears and a 31-spline ARB Air Locker (PN RD119) to work in con­junc­tion with fac­tory big bear­ing axle­shafts. The stan­dard case is not as de­sir­able as a nodu­lar case, but it is far more com­mon. If you set up the gears your­self, you can have a sim­i­lar setup for around $1,200 that will live a long life be­hind a mild V-8 and 37-inch-tall tires.

With more en­gine, big­ger tires, or a heavy rig, the fac­tory parts might not be strong enough. The 9-inch ben­e­fits from huge af­ter­mar­ket sup­port though, so much so that it can be over­whelm­ing. We built a third mem­ber with en­tirely new parts from G2 Axle & Gear and ARB that is sig­nif­i­cantly stronger than the fac­tory third due to bet­ter ma­te­ri­als and big­ger bear­ings, but it also cost us twice as much money. We spent our money on a G2 third mem­ber (avail­able

in ei­ther alu­minum or nodu­lar steel), stronger “Day­tona” style pin­ion sup­port, a G2 ring-and-pin­ion, and a full in­stall kit with Timken bear­ings. The G2 Axle & Gear com­po­nents were paired with ARB’s RD99 Air Locker, which is sim­i­lar to the RD119 ex­cept it ac­cepts larger,

11⁄2-inch-di­am­e­ter, 35-spline axle­shafts, mak­ing it well matched to chro­moly axle­shafts and fab­ri­cated 9-inch hous­ings that are reg­u­larly found un­der bug­gies and hard­core rock­crawl­ing rigs.

If you own a Tro­phy Truck or Ul­tra4 car, or sim­ply must have the very best, it’s time to look at Gear­works com­po­nents. The Gear­works third mem­ber is de­signed to ac­com­mo­date a larger, 10-inch ring gear for in­creased strength with no penalty in ground clear­ance. The case uses huge, 4-inch bear­ings than can ac­cept axle­shafts up to 2 inches in di­am­e­ter.

We bolted the 10-inch ring gear to ARB’s RD99CE com­pe­ti­tion Air Locker. “We love a chal­lenge,” ARB USA Pres­i­dent Doug Pet­tis says. “There’s only so much room in­side of a 9-inch hous­ing, so in or­der to in­crease the case strength by 290 per­cent we had to get cre­ative with re­gards to de­sign and ma­te­ri­als.”

The re­sult is the strong­est se­lectable locker ever of­fered for the

9-inch axle thanks to deeper tooth en­gage­ment and forged in­ter­nals. Again, the price roughly dou­bles from the G2 com­po­nents and RD99 Locker, and is four times higher than our re­built junk­yard third mem­ber.

Which third mem­ber is right for you de­pends on a va­ri­ety of fac­tors, in­clud­ing your bud­get and in­tended use. The beauty of the

9-inch is that you can mix and match parts un­der your rig, up­grad­ing as com­po­nents fail or your bud­get in­creases. Even though the

9-inch hasn’t been found un­der a new Ford in decades, this axle isn’t go­ing away any time soon.

3 3Dif­fer­ent-sized bear­ing caps are avail­able from the af­ter­mar­ket. The stock case uses 3.062-inch bear­ings that are well matched to the orig­i­nal 28- or 31-spline axle­shafts. The G2 third uses 3.25-inch bear­ings that ac­cept 1.5-inch, 35-spline axle­shafts. The Gear­works third uses huge,3.812-inch bear­ings that sup­port up to 2-inch, 45-spline axle­shafts.

6 6Here is a closer look at that third pin­ion bear­ing that the 9-inch is fa­mous for. In ad­di­tion to there be­ing more ma­te­rial, the type of ma­te­rial is also a fac­tor in strength. Gray iron has a ten­sile strength of 30,000 psi, while nodu­lar iron is 65,000 psi.

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