Review: All-Pro Off Road Profields - Heavy Duty Birfield Joints Short Cuts

| Toyota Tech | Toyota Section | |

Written By: Jay Kopycinski 2/2004 (Updated 1/2005, see notes below)

Typical broken stock Birfields

It's no secret that Toyota truck and 4Runner straight front axles are beefy. Those stamped sheet metal carcasses and rotating parts can take a lot of abuse, far more than the designers ever planned for them to withstand. But, the bar has been raised, and more Toyotas are finding their way onto tough terrain and hard core wheeling trails.

With these new demands placed on these axles, it's inevitable that breakage can occur. The weakest links in this front axle are the Birfield joints that transmit power from the inner axle shafts to the locking hubs. The "Birfield" itself consists of the constant velocity joint and the outer axle shaft that is splined to mate to the locking hub.

Inside each joint are 6 large ball bearings, an inner bearing race, and an outer cage. Occasionally a stock Birfield will fail when the outer axle shaft breaks. However, the more typical failure mode is that of the "bell" portion of the Birfield joint cracking and shattering as seen here. Birfield joints are strongest when the tires are pointed straight ahead and grow weaker the further they are turned from this position.

New Profield heavy duty joint Heated treated "bell"

Profields are new, heavy duty Birfield joints that have been strengthened through an advanced heat treatment and cryogenic freezing process. All-Pro Off Road worked with rock crawling axle expert, Jack Graef of CTM Racing, to develop this product.

We received a set of Profields for installation and test. They arrived individually boxed and each joint was greased. We disassembled our front axle as we have many times while replacing stock Birfields and installed the Profields. Prior to assembly, we packed a bit more grease in the joints for extra measure and slipped them in the knuckles.

Installed in spindle

With the Profields installed we hit a couple of local extreme rock trails. Our rig weighs about 3700 lbs. and sits on 38" Swampers. We wheeled some gnarly rocks and big ledges. The tires were stuffed into some tight spaces and against some vertical faces, and the Profields held together. We also tried a number of small block Chevy motivated launches up a steep waterfall face and bounced the front end pretty violently. Still no front axle failure.

UPDATE: January 2005
I managed to destroy both of the Profields after putting about a dozen hard core runs on them. I had completed a number of Arizona trails and a few trails in Victor Valley. One failure occurred while the front tire was wedged between two boulders and the other failed while the tire was climbing a vertical face.

Broken at the outer splines Another view of the splines Cracked and spread outer bell

One Profield broke out at the end near the hub splines. It broke at an angle and spiraled out, cracking the outer hub dial. The second Profield failed when the inner race cracked, followed by the outer bell cracking. I've heard various survival results from other Profield owners. It seems that strength of the units may vary somewhat.

Contacts Related Links
  • All-Pro Off Road
    Department 4x4Wire
    541 N. Palm Ave
    Hemet, CA 92543
    Telephone: (909) 658-7077
    Web site: All-Pro Off Road

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