"Full floating axle" explained

[mcgarrett]

I confess I'm still quite foggy on the meaning of the term "full floating" axle and would appreciate a clearer explanation and perhaps some diagrams and illustrations. I, too am a visual learner and pictures work the best for me, but any clarification would be appreciated.

[1952henry]

A full floating axle has the axle tubes tapered at the end. The ends are machined on the outside to accept bearings, usually tapered. The hub fits over the bearings and is retained by two nuts. These also set the preload on the bearings. The brake drum, in most cases is held onto the hub by 2-3 screws. The axle shaft has splines to engage the differential on one end a flange on the other. The flange fits over studs screwed into the hub. The only function of the shaft is to transmit torque from the differential to the hub. The wheel bearings take the weight. You can break a shaft, and only lose torque, not the wheel.

[1952henry]

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[1952henry]

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This is a Timken full floater from my MH F3, which was a HD 3/4 ton. Excuse the grunge, this axle is junk, thanks to failed pinion pilot bearing. It did serve a purpose as a test mule for my diy pinion puller. Better axle is still under parts pickup.

[Newc]

Full Floaters were introduced by Ford in the '34 1 1/2 ton trucks . A big deal cause of the load capacity available. Resulted in Big sales increase. Newc

[1952henry]

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Marmon Herrington used a semi- floating design on the front end, which was a modified rear. From the F1 to the F6, the hub was semi- floating. AFAIK, most if not all manufacturers in that era used a full float design on the front ends. Dodge went to semi float front hub in the 70s. Now most newer pickups have that style. Both MH and newer style hubs would be perhaps considered 3/4 floating

[Steve S.]

In a full floating axle, the entire load is carried on the axle housing. There is no weight carried by the axle shaft. With a full floating axle, the axle shaft can be removed, and the vehicle can still have its loaded wheels on the ground. Semi, or 3/4 floating axles carry some of the weight on the axle shaft and generally the axles cannot be removed without removing the wheels also. Trucks of 3/4 ton capacity and up almost always have full floating axles. As noted above Ford changed over to full floating rear axles in 1934. Too many Ford trucks were breaking axle shafts because the were not only carrying payload, but delivering driving torque to the wheels.

[JayChicago]

Steve S
Thanks for a clear explanation. Thanks for starting at the basic differences, for those of us who know nothing about this. Now I can finally understand the concept.

[Flathead Fever]

Half-ton modern pickups have a single ball bearing axle bearing just like modern cars have. They are not made for heavy loads. Full floater axle have two tapered roller bearings with replaceable races just like the front wheel bearings only much larger to carry the weight. The bearings also run in gear oil from the differential. It runs down the tubes and fills a reservoir in the hub. I always prefilled that reservoir on the trucks at work before I slid the axles in. The axle does not carry any weight, instead its "floating" suspended between the hub and the differential carrier. You can remove the axle and still roll the vehicle. We had a lot of 3/4 and on up trucks at the phone company with full floater rearends. Some you can slide the drum off and leave the axle and bearings in place and replace the brake shoes, others you have to remove the axle, then remove the drum, hub and bearings to get to the brakes. Then you always install a new grease seal because if it leaks, it soaks your brake shoes with gear oil. I had a '33 1 1/2 ton truck that had tapered rear axles with keyways, just like an early Ford. I never was able to pop those big drums off, I didn't have the correct puller. The next big truck project I bought I made sure it was a '34 with full floating axles, like normal trucks have so I can work on it. Plus, the '34 truck has nice little Ford hubcaps.

You adjust those rear floater bearings just like you do front wheel bearings, no lateral endplay but no preload or just barely a little since they ride in gear oil all of the time.

With the Ford Floaters you get this nice little axle cover held-on with two screws.

[Model51]

There are a couple of detailed illustrations in the EFV8 club book on the 1935-1936 Ford Trucks in case you want to see the finer points of the full floating rear axle.