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Toyota Axle Upgrade Guide

Posted in How To on March 1, 2008 Comment (0)
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Toyota pickup axles are renowned for their light weight, low cost, and high strength. Although they don't offer the ground clearance of portal axles or the massive ring gear of a Corporate 14-bolt, these axles are popping up under a wide variety of vehicles beyond Toyotas, including Jeeps, Samurais, and buggies, because of the features mentioned above. As good as they are from the factory, like most components they can still benefit from advances made in the aftermarket.

Stock Front Axle
Toyota used a solid front axle in the '79-'85 pickups and 4Runners. All of these axles were 55.5 inches wide from wheel mounting surface (WMS) to wheel mounting surface and came with solid front disc brakes and closed knuckles with Birfields. These axles also came with push-pull steering and a torque-rod bracket welded to the housing. They use the same 8-inch third member and 1-5/16-inch axleshafts as the rear axle, simplifying part swapping. The Birfields are 30-spline at the hub, and the inner axles are 27-spline at the Birfield end and 30-spline at the differential end. Earlier axles had no trussing on the long side, but over the years Toyota increased the size of the truss under the housing until eventually it spanned the long side of the housing by 1984.

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Poly Performance is an official Longfield retailer and also sells its own 4340 chrome-moly axleshafts.

Front Axle Upgrades
Aftermarket Birfields
By far the weakest link in Toyota axles are the stock Birfields. These joints have limited angularity and are prone to cracking with the steering at full lock and power applied. Long's Enterprises developed Longfields that address all of the factory shortcomings. The latest generation of Longfields are 30-spline from the differential to the hub and are made from chrome-moly. The inner race is machined from 300M and is smaller than stock to add thickness to the outer bell. In addition to the strength, Longfields are able to provide a much tighter turn radius than stock Birfields due to their tapered design.

Inner Axles
Aftermarket Birfields used in conjunction with stock axleshafts can transfer the weak link to the splines where the shaft mates with the Birfield. Poly Performance sells chrome-moly inner axleshafts that do not neck down like the stock shafts and which eliminate the need for a C-clip to retain the axle.

Front Range Off-Road Fabrication hub studs are stronger than stock to resist shearing off in high-torque applications.

Upgraded Hub Studs
When hub studs shear, they often render the wheel hub useless. In order to cure this problem, Front Range Off-Road Fabrication developed hardened chrome-moly studs that feature rolled splines and include high-quality locknuts for proper retention.

Chrome-Moly Hubs
After upgrading the Birfields and inner axles, the stock hubs become the weak link. Drive flanges from an FJ80 Land Cruiser can be used to replace the hubs, but Long's Enterprises has a more practical solution for those who don't want their front driveshaft spinning all the time. Long developed 4340 chrome-moly hub gears that are significantly stronger than stock and won't strip the splines off of your high-dollar aftermarket Birfields.

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Beefed Steering Stops
The stock steering stops consist of a small piece of triangular metal strap-welded to the housing. Adding huge tires and hydraulic-assist steering can bend the stops, causing the Birfields to bind and break. To prevent this, Inchworm Gear makes fully boxed steering stops out of heavy-gauge steel. The new stops weld directly in place of the factory steering stops and offer greatly increased strength.

Crossover Steering
From the factory, solid-axle Toyotas came equipped with push-pull steering that was used in conjunction with a torque rod. The torque rod limits articulation, but removing it can result in broken drag links and steering arms. All-Pro Off-Road offers a kit that replaces the entire steering system with a crossover configuration using an IFS Toyota steering box, forged steering arms, 0.250-wall DOM links, and 23mm FJ80 tie-rod ends. The tie rod is also moved above the springs and behind the axle for greater protection on the trail.

ARP makes hardened Toyota knuckle studs that are available exclusively through Front Range Off-Road Fabrication.

Upgraded Knuckle Studs
Just as with the hub studs, knuckle studs can shear as well. This is often an issue when wide, heavy tires are used in conjunction with rims with minimal backspacing. Front Range Off-Road Fabrication is the sole distributor for ARP knuckle studs. The new studs are hardened chrome-moly and feature rolled splines for additional strength.

Vented brake rotors and upgraded calipers are available from Marlin Crawler and provide a significant increase in braking power and fade resistance.

Brake Upgrades
The factory brake calipers and solid rotors only do a marginal job of stopping small stock tires, so when you add more weight and leverage they are really overwhelmed. Vented rotors from an '81-or-later FJ40 can be used in conjunction with calipers from an IFS pickup for improved braking force and less fade. The later V6 calipers had larger pistons that provide more braking force than the earlier IFS calipers.

All-Pro D60 Hybrid
Many of the aforementioned upgrades have been bundled into one beefy axle from All-Pro Off-Road.

All-Pro replaces everything from the knuckles out with 1-ton components. The company's hybrid axle features F-450 U-joints, bearings, and hubs with Wilwood calipers and rotors that provide increased stopping for large tires. The brakes fit under 15-inch wheels and even retain the stock 6x5.5 bolt pattern.

High-Pinion Third Members
FJ80 Land Cruisers used a front third member that is interchangeable with the solid axles found in pickups and 4Runners. The Land Cruisers used a high-pinion third member with a reverse-cut ring-and-pinion that is stronger than the low-pinion third member used in stock front axles and which offers 4 inches more ground clearance for your driveshaft and pinion flange.

The factory third member in the front of mini-trucks and 4Runners uses the same low-pinion third member as the rear axle. The low-pinion can cause the driveshaft U-joints to bind with large lifts or extremely flexible suspensions.

Axle Truss
Large tires increase leverage, which can result in bent axlehousings, particularly if the vehicle is jumped. All-Pro Off-Road sells a truss that can be welded to the top of your axlehousing for improved rigidity with no loss of ground clearance.

Stock Rear Axle
Toyota used a solid rear axle with an 8-inch ring gear and 1-5/16-inch 30-spline axleshafts exclusively through '95, and even later in some Tacomas, T100s, and 4Runners. Early axles were 55 inches wide to match the front solid axle and increased by 3 inches when the switch to IFS was made in 1986. With the added width in '86, the axletubes grew larger and the brake drums were also enlarged from 10 inches to 11.6 inches. All pickups and '89-and-earlier 4Runners used leaf springs, while later 4Runners used a four-link and coil-spring suspension, making these axles more difficult to retrofit into other vehicles.

Rear Axle Upgrades
V6 Third Members

The third member from a V6 or 22RTE turbo-powered truck bolts directly in place of the standard four-cylinder third members yet is stronger due to the four spider gears, larger ring-and-pinion, larger bearings, and stiffer third-member housing.

Upgraded Axleshafts
Poly Performance offers upgraded axleshafts made from 4340 chrome-moly. The shafts accept stock bearings and brakes and use rolled splines and a tapered design for maximum strength.

View Slideshow
Front Range Off-Road Fabrication's full-floater kit includes a number of upgrades in one package, including disc brakes and chrome-moly axleshafts.

Rear Disc Brakes
Larger-than-stock tires can lead to increased braking distances due to the added leverage and weight of the bigger meats. All-Pro Off-Road has a bolt-on rear disc-brake kit that provides shorter stopping distances, easier maintenance, and less unsprung weight.

Full Floater
Several of the above ideas have been integrated into one comprehensive package from Front Range Off-Road Fabrication. The kit converts the rear semifloating axle to a full floater using custom-machined and factory Toyota components. In addition to the increased load-bearing capacity and safety, the FROR full-floater kit also incorporates chrome-moly axleshafts and disc brakes for even greater strength and performance.

Axle Truss
Adding an axle truss can strengthen your axlehousing and resist bending the tubes - particularly if you like to jump your truck. Downey Off-Road offers a weld-on truss that incorporates a polyurethane bushing in the middle to accommodate a traction bar as well.

Upgrades for Front and Rear Axles
Solid SpacerMost aftermarket gearsets come with a crush sleeve that fits between the pinion bearings and is collapsed during the installation process to set preload.

A solid spacer is available from All-Pro Off-Road that eliminates the possibility of excess backlash and the need to retighten the pinion nut.

Electric lockers were a factory option on TRD Tacomas and some 4Runners. Inchworm Gear stocks new electric lockers and can equip them with gears far lower than ever offered from the factory.

Electric Lockers
Toyota used an 8-inch centersection with a factory electric locker in TRD Tacomas and some 4Runners. With minor housing modifications, this third member can be retrofitted into any 8-inch housing for an open differential on the road with the traction of a spool at the flip of a switch. FZJ80s even came with an optional high-pinion electric locker in the frontend. Factory ratios were 4.10, 4.30, and 4.56, but Inchworm Gear can set you up with an electric locker and the related wiring in any gear ratio you desire.

Low-profile drain plugs from BudBuilt are less likely to be damaged on the trail than traditional hex-head plugs.

Low-Profile Drain Plugs
The factory drain plug on Toyota housings is a hex-head plug that we have seen get knocked loose on more than one trail ride. BudBuilt stocks low-profile drain plugs that use an Allen wrench for removal, so they will stay put on the trail and you can still remove them when necessary.

4Crawler's high-clearance axle kit is not for the weak of heart, as it requires cutting and welding on the axlehousing. The added strength and ground clearance make it well worth the effort though.

Diff Armor
The factory differential housing is stamped steel and can be dented and contact the ring gear during hard contact with rocks. All-Pro Off-Road's diff armor welds to the factory housing and protects the ring gear from any impacts.

4Crawler Shaved Diff
A more complicated way to armor your axlehousing: Remove the drain plug completely and gain ground clearance with 4Crawler's high-clearance axle kit. This kit requires you to cut off the bottom of your axlehousing and weld in the supplied pieces to realize the above benefits.

Diamond Axles axlehousings are the ultimate in Toyota axle upgrades, with more ground clearance, increased strength, and the ability to add width.

Diamond Axlehousings
The ultimate in strength, front or rear, comes in the form of Diamond Axles axlehousings. These all-new housings feature 1/2-inch-thick mounting flanges, 3/4 inch more clearance than stock housings, and 1-inch-thick steering stops on front housings. Diamond axles can be ordered in custom widths with a variety of options including Dana 44 or Dana 60 knuckles, semifloater or full-floater ends, and driver- or passenger-side drop.

Sources

Poly Performance
San Luis Obispo, CA 93401
805-783-2060
www.polyperformance.com
All-Pro Off-Road
Hemet, CA 92543
951-658-7077
www.allprooffroad.com
Inchworm Rock Walkin' Gear
Shingle Springs, CA 95682
530-677-8111
http://www.inchwormgear.com
Marlin Crawler
Fresno, CA 93703
559-252-7295
http://www.marlincrawler.com
Downey Off-Road Mfg.
Santa Fe Springs , CA 90670
310-949-9494

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