I have a 1958 F600 that has hydraulic drum brakes with a vacuum booster under the cab. Today I was at the truck salvage yard and they had a front axle out of what they said was an early 80's F600 or F700 with disc brakes. I was surprised to see that it had the same 6 on 8.75" bolt pattern that my F600 has. I measured the CTC distance between the u-bolts and it was 32"- the same as my truck. I didn't measure the total width.
Can anyone tell me if this axle can be swapped into my truck? Does anyone know of any reason it wouldn't work if the width is correct? Are there any issues with my vacuum booster which only has one brake line coming out of it?

 

Is the axle width the same. If it is, it sounds like it should work. If you are going to discs in front from drums, you will need a different master cylinder and probably a proportioning valve. You might see if you can get the valve off the doner vehicle. you could also, pull the master cylinder from the doner, but I'd go ahead and get a new one, but you might use the doner one for exchange.

 

I'm not aware of a front axle swap for discs being done on a truck that big by any of the posters on this board. You may well be on your own here. It sounds like you've already checked all the critical measurements. The best I can advise you to do is double and triple check all your measurements and make certain that it will bolt in correctly before you lay out any cash. Also check the steering linkage to make sure that you'll be able to get it hooked back up correctly.

It would theoretically be possible to retain your original master cylinder and booster, but it could be a bit complicated. Your master cylinder will most likely have a residual pressure check valve in it to hold a minimum amount of pressure on the system at all times to keep the drum brake wheel cylinder cups sealed against their bores. The master will need to be disassembled and the valve will need to be located and removed. If you leave it in, the disc brakes will want to drag all the time. An external residual pressure valve would have to be installed in the rear brake line. In addition, you will likely also need to install an adjustable proportioning valve in the line to the rear axle to balance the rear drum brakes to the discs and prevent premature lockup in the rear.

HOWEVER! In the name of safety, I always advise that a single circuit master cylinder system be replaced with a dual circuit master for EVERY installation short of a strict restoration. For you, this would also require replacing the booster. If you actually intend to use the truck for a truck, then that goes double. Nothing worse than the thought of broadsiding a busload of kids with a full load on because a blown hose or line took out the entire system. There are many dual circuit master conversion kits available to choose from. It wouldn't hurt to give it some thought.

 

ABSOLUTELY!!!


I'm going to stay with my front axle but I am going to try to put a dual res/hydraulic boosted MC on mine.

I'm certain I'll need to use a proportioning valve and I'll have to experiment with adjustments etc..... but I think the added safety of a "split" system is well worth it!!


I'll also add that the frame width is the same and just about any axle will probably work. Just make sure that you don't screw up the steering geometry


Regards,


Rick

 

The spring mounts on the axle should line up with the ones on your truck. Trucks have a standard frame width of 34". Exception being the pre '52 trucks, while being 34" in the back, they neck down at the front by a couple inches, which squeezes the springs to the middle. I'm guessing the track width of the newer axle wouldn't have allowed the swap tho, without the tires sitting outside the front fenders. The newer truck probably had a front track width a good 8" or so wider. I was investigating axle swaps to get away from the 5x8" mount pattern on an F6. At least I measured twice before buying the parts and getting them home......

Good luck with your brake swap and keep us posted on how it works out for you..

 

Did you buy the front axle?


I have a 1956 F600 and want to replace my axle as well.


Regards,
Al

 

You posted this thread in the wrong forum, this forum is for 1948/56 F100 and larger trucks.

You should have posted this thread in the LARGE TRUCK forum (for 500 and larger series trucks).

The Girling disc brakes used in these trucks, from what I've read here on FTE, were problematic.