3/4 ton 4x4 front axle width questions

[chevytruckguy70]

When it comes to 69 and 70 trucks, I've been a 2wd guy through 5 trucks. Now I've jumped into a new project that's a retired 1970 3/4 ton 4x4 fire truck.

The fire dept swapped out the front axle for a later model dana 44 with disc brakes and added 5 extra leaf springs in hopes of controlling the 300 gallons of water loaded in the bed. I have the original drum brake axle, it came with the truck when I bought it.

Now my question. The disc brake axle is 1 1/2 inch wider per side than the drum brake axle. This causes the front tire to stick out of the front fenders and, now that I've lowered the truck back to factory height, also causes the tires to rub the fenders when turning. Is it normal for the disc brake axle to be wider than the drum?

I measured the drum brake from ball joint to ball joint and get 54". Measuring the same locations on the disc brake axle I get 54 1/2". Measuring from wms to wms on the drum axle I get 69". The disc brake axle measures 72". This tells me the extra length is located on the spindle assemblies. Can this be swapped out with other disc brake spindles to be corrected or do I have to convert back to drum brakes to get my wheels back in the fenders where they belong?

BTW........ This truck has 15,054 original miles on it. You've got to love fire departments!

[RPBurris]

Nothing constructive to add...just letting you know how jealous I am. Looks like a great truck. I know all those firefighters like to wash trucks all day so I am sure it is a very clean rust free truck with low miles. Granted it probably had 2400 lbs of water in the back of it most of the time but it looks great.

[flyingtim01]

I can't speak to the width of the drum brake axle, but the 4x4's came with two different Dana 44 front axles. Half tons had a smaller hub version, and 3/4 tons had bigger hubs and bearings. I imagine they put the heavier front axle in it, seeing as how they were concerned about the water tank, though I can't say for sure one way or the other if the smaller hub version is any narrower from the hubs out. Although, I am pretty certain you can swap your spindles, bearings and hubs out for the half ton version of everything and retain your disc brakes. Check with the guys over in the 4x4 forum, you'll probably get a much more helpful answer!

[flyingtim01]

Great looking truck, btw! I credit an old brush fire truck I saw when i was kid for my love of 4x4s.

[chevytruckguy70]

Yes, the truck is completely rust free except the bed floor. They had a foam rubber mat under the tank and pump that held in water and completely rotted the floor away. Other than a couple of dents, antenna and siren holes and oil leaks she is perfect. I had bought a 69 4x4 to restore and then this truck just fell in my lap.

Anyone interested in a 69?
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[Husker]

Front axles on 4x4's are wider than rears. I have a 70 GMC and a 76 Jeep CJ5 and both are like that. Not sure of the width for sure. I added spacers to the rear to even them up, makes them look better I think. 3 inches total like you state sounds about right. What size tires and wheels you running? Very nice looking truck.
Ron

[chevytruckguy70]

It has 16.5x10 with 33's on them. The Fire department actually put those on. The new front axle has 9/16" lugs while the rear has 1/2". That is a pain.

My 69 is a 3/4 ton 4x4 but the front and rear line up together. That's another reason I think it must be the disc brake system that is wider.

I've attached some pics of my 69. It is a 4 speed truck, in a few pieces at the moment.

[special-K]

I never knew the axles varied in width at all,and I've had K/20s (12 or so) for a few decades now. I have never known for any difference in the width to make such a difference with the same tire/wheel. From your picture it looks like going to the '70 axle won't help. Those tires are sticking out far more than the difference in axle width. Those 9.75 x 16.5s came in different offsets and it looks like the FD used rear duplex wheels designed to increase track. I think you are taking the hard route making your truck fit your wheels & tires. 12.50/33s will fit a stock K/20,from any of these years,when mounted on the right wheel. I'd either use springs that hold the front up enough to where it was for the FD or go to a narrower wheel,or at least a 9.75 with more back space. I have a set that was labeled for trailer use that are offset a couple inches less than a pair I have from a '72 C/30 mounted on the rear. All the 4wds have a wider track width than the rear. When I'd run the narrower ones on the front the track was about the same. When they were on the rear the front track was way wider,like how yours look.

[chevytruckguy70]

I appreciate the info. The current wheels and tires will be coming off for a more traditional truck rally look. The current front and rear are the same size which is what caused me to look into the width issue. My 69 K20 still has the front drums with spoked wagon wheels which are 10x16.5s and they are under the fenders. I took those and put them on the 70 to ensure it wasn't a wheel issue but they also stuck out on the front end. Thats why I started measuring everything.

I know in the late 80s thru 98 that the k20 front end was wider than the rear (which I hated) but I do not remember seeing that on any other model year. I was hoping mine was some odd ball thing that could be remidied easily. I've got some friends who go through front ends relatively quick due to rock climbing and we are going through their axles in search of the answer. Hopefully there is one.

Special K, can you send a picture of your K20? Preferrably down the side from the front. I'd like to compare it with mine. Thanks.

[special-K]

The attached photos show the Orange & White '72 has 8" wheels & 285/75 -16s,lifted a couple inches (add-a-leaf). The white '72 has 8.25" wheels & 12.50/33-16.5s,no lift and settled a bit. The Blue & White '72 has 10" wheels & 12.50/35-16s,lifted 6".

[chevytruckguy70]

Thanks for the pictures. I've got to say i love the Blue and white one. I believe that is the best color combination.

All of the trucks you've shown are disc brake trucks and the front to rear spacing seems the same. I couldn't see the green truck you were refering too with the spacers.

I think I just need to search other front ends and find the right one.

Thanks again. Here's what I plan on my fire truck looking like......one of these days.

[special-K]

Nice! That fire truck looks like it will be pretty easy to do it with

[mcmlxix]

Rather then change axle parts, find a set or wheels with the correct offset and backspacing to bring the outer edge back where you want it....

What axle is under the front now? Dana 44? 10 Bolt? Dana 60?

[Beelzeburb]

Originally Posted by mcmlxix

What axle is under the front now? Dana 44? 10 Bolt? Dana 60?

That's an excellent question.
BOM numbers might help figure out what it came out of originally. I'm thinking this front axle didn't come out of a standard 3/4 ton Chevy/GMC.

I happen to have both 1/2 ton and 3/4 ton disc brake front D44 axles from SRW trucks at my disposal. I measured the WMS to WMS width on each real quick.

'77-'79 D44-8F 1/2 ton = 67.5"
'77-'80 D44-8F 3/4 ton = 69.5"

Possible theory: Perhaps it came out of a dually truck and has the extra DRW width hub and rotor assembly? Those honking big hubs would be pretty noticeable though.

[special-K]

I all the axle swapping of so many axles I've done and any variation in width has never been an issue. In fact,I never had a reason to ever measure any of them. The DRW would be a Dana 60 and the extra hub spacer is unmistakeable. I would make any adjustment with wheels if the axle in there works fine.