Eaton Fuller Intermediate Companion Flange
*New! GM/Chevy passenger drop 6 bolt round now available for preorder!*
Order a companion flange, as a substitute for housing preorder.
By purchasing the companion flange, you will be considered as a preorder for a housing. Once all of the (qty 10Female Eaton Fuller & 6 Ford male) companion flanges are out of stock, you will only be able to preorder an adapter, indicating your desire for one on the next run. The qty scheduled for the next production run will be finalized November 3rd. Currently there is qty 10 Ford and 6 GM scheduled, if you haven't bought a companion, or a housing on preorder before Nov 3, you will have to wait for the next run in 2026.
FSO-64x4 adapter Companion Flanges
Two required for a complete setup.
Offerings Available:
Transmission Side 38 Spline Female
Transfer case Side 34 Spline Male
The 38 Spline Female has been tapped to accept a M12X1.75 bolt. The bolt pattern is square on a 3.75" Bolt Center. Four grade 10.9 Bolts will be supplied with this companion.
Additional Information:
This is a two-piece setup. It requires two separate companion flanges, to transmit power to a Transfer Case. It also utilizes the yoke nut, used on factory end yokes.
It is possible to use only the Transmission side companion and make your own Transfer Case side. For those using anything less than a 34 spline T-case, or for those wanting to save on total costs, you will have to make your own until 32 and 31 spline production is ready.
Another option to transmit power from an Eaton Fuller transmission, is to make your own "Spud Shaft". This is viable because the adapter housing sets main shaft endplay, not the output yoke. The involute splines don't require a register or end yoke nut. This is usually done with an old output yoke, lathed down to a concentric shape, that is then welded to an old transmission output shaft cut to length. This must be done by both a competent lathe operator and welder. Concentricity is key, so that the hub seal surface does not leak, eliminating vibrations.
If you already own both the output yoke, can scrounge a burnt-up transmission to donate an output shaft, an have the skills to do so you'll be money ahead. Otherwise, Eaton Fuller output yokes are usually $250-450 if available.
https://www.northerndrivetrain.com/category/cat_flanges_SplinedBore_38Spline_1-998-38invol.html
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