Drag Race 101: Nine Lives Part III
Aftermarket Pinion Supports
Mark Williams manufactures 9-inch Ford pinion support assemblies for a number of applications (everything from roundy round cars to Pro Mods and everything in between). Assemblies are available for standard 28 spline pinions and 35 spline large pinion pro gears. The support housings are CNC-machined from aircraft quality aluminum and use either oversized tapered roller bearings or low friction angular contact ball bearings. All pinion supports come pre-assembled. The bearing pre-load is set through the use of a solid hardened pre-load spacer rather than a crush sleeve or stack of thin shims. The spacer is factory machined to the required pre-load for each assembly. Pinion seals are included. Housings are drilled to accommodate the 7/16” studs used in all MW cases. That doesn’t preclude the use of these custom pinion supports in a stock Ford case. By using special reducer bushings from Williams (part number 57606) and accompanying studs (part number 57609) the housing can also be used with stock style 9-inch Ford cases equipped with 3/8-inch threads. All MW 9-inch yokes and couplers are designed to work perfectly with MW pinion supports. If you use the support with a stock Ford yoke, it must be shortened for proper thread engagement.
Williams also offers a nodular iron ball bearing pinion support that is identical in appearance to a standard Ford (OEM) support and accepts a 28-spline pinion shaft. In order to reduce friction and bearing pre-load, the assembly uses an angular contract ball bearing in the rear and a heavy-duty Timken tapered bearing in the front. With this combination, the initial bearing pre-load can be reduced from 18-20-inch pounds to 3-5-inch pounds. These pinion supports are pre-assembled and the bearing pre-load is factory set using a hardened solid spacer rather than a crush sleeve or shims. The support will accept a stock Ford yoke or a NASCAR style pinion yoke. Options include ceramic balls for the angular contact bearings as well as a low drag Teflon pinion seal (for use with steel pinion yokes only).
You can specify a custom 9-inch center section with either a standard gear or a Pro gear. What’s the difference? Williams states: “Pro gears are made from 9310 and then heat treated. It is a softer alloy than the 8620 Street gears. The softer 9310 alloy allows the gear to absorb higher impact loads that are generated in drag racing without developing cracks. A harder 8620 street gear could shatter under the same loads. As a side effect the “Pro” gears are not the best choice for street use, as they will wear faster. Also available in the “Pro” gears is a large pinion with a 35-spline shaft for high-powered applications. This requires a bearing change in the pinion support as well as a 35-spline pinion yoke. Gears termed 9-1/2″ are also available for the 9″ third member. They offer a slight strength advantage over a standard 9″ gear.”
Pro Stock Specials
The Williams-designed 9-1/2” gears are manufactured in 9310 alloy with a 32-spline pinion. They’re available in the following ratios: 5.00, 5.11, 5.14, 5.17, 5.20, 5.25, 5.29, 5.33, 5.38, 5.43 and 5.50:1. Basically, this is a Pro Stock or NHRA Comp Eliminator setup. The gears (and consequently, complete 9-1/2 ring gear Pro center sections) are available with Supra-Fin™ processing that reduces friction and eliminates material transfer normally found in the break-in process. Williams also incorporates a special Sub-Zero thermo-treatment to eliminate the possibility of retained austenite. What’s “retained austenite?” When you quench steel (quenching will harden it) the process will not always form 100% hardened steel, otherwise known as martensite. Instead of the 100% martensite condition, there will always tend to be some percentage of retained austenite. Austenite is the state steel must reach prior to hardening. Retained austenite is not stable and over a period of time, will change into martensite. So far so good, but “new” martensite will be untempered and as a result, it’s brittle. That’s why, in a particularly high impact situation such as a Pro Stock rear, it’s a good idea to eliminate the possibility of retained austenite.
Back to the big boy center sections: When those Pro Stock rears are assembled, Williams notes: “We incorporate a ceramic dual opposed angular contact bearings pinion support that is lighter, while reducing friction and adding rigidity to the pinion. A low drag pinion seal, used in conjunction with our aluminum pinion yoke reduces the pre-load drag to about 5 inch pounds.“The proven MW Thru-Bolt case features the new Sure-lock™ adjuster system that makes other retention methods obsolete and prevents adjuster back out. All units include a Computer pickup ring with two magnets.”
That wraps up this segment of our “Nine Lives” series. Stay tuned. There’s one more to come.
Source: Nine Lives
Mark Williams Enterprises
765 South Pierce Avenue
Louisville, Colorado 80027