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I had to send this in. You just don't see many old tandems like this 53 GMC. I found it while on a brush fire and vowed to return someday to look it over more closely. The guy offered to sell it to me. HMMM...

https://www.facebook.com/photo.php?...m.338521483018731&type=1&theater

Cool looking truck.
Am I right by thinking the tamdems were an aftermarket item in those years?
Hopefully the price is right for you and if not, leave your number so that if he ever drops the price to call.

I saw an early 50's Chevrolet flatbed a few years ago that had tandem duals. The first axle was the drive axle and the second axle was a tag. It appeared, from the marks on the frame, that the original axle had been removed and replaced (on a lengthened frame) with the tandem set.

My guess would be the company that installed the fire bed on the truck also reworked the axles to carry the load.

I agree - the frame would have to be lengthened to accommodate the tandems. I have never seen one - looks like a pretty clean job of it. I'm guessing this was a pumper-tanker, and the tandems were necessary to carry anything over 500 gallons.

It begs many questions: would you use a 2-speed rear end? (almost definitely, in my mind). Brakes on both axles? (you'd sure want them!). Any connection to the military tandems that were offered in WWII and after by GM? Those were true tandems, tho, not just a tag.

Looks like maybe the truck was made by General, in Detroit? Just a guess . . .

-Michael

That's a cool looking truck! I hope you can get it.

GMC offered an Eaton 22,000 tandem in the 400 Series in the early 50's. It was the tandem that had the interaxle drive shaft going over the front banjo housing. They didn't build them very long because they couldn't match the reliability of the Rockwells that had the throughshaft in the forward axle. This one appears to be a 350 series. However, in 1955 GMC built a 424 for the government. It looked like a 370 series, but It had a 302, twin disc clutch, 5 speed and single axle. I have a parts supplement dated November, 1951 where it lists a HC451, HC 454 and HFX 652. This may have been something specially built for the government. My parts book has no illustrations, so I don't know what they looked like. I really doubt that a drag axle would have been used on a Fire truck. As far as weight goes, we hauled 1,800 gallons of Diesel on a 450 with a single axle.

Here is a picture of the 424 GMC the way I bought it.

https://plus.google.com/10819770718...2841998386&oid=108197707187186692269

I removed the expanded metal grill, installed a chrome grill from a 370 and shortened the wheelbase to accept a fire rescue body to make a rolling tool shed out of it.

These early '50's G.M.C.'s tandems are very similar to a Hendrickson set-up.The front axle is powered (directly) through a transfer case. The rear axle is powered by vacuum,(when needed),through a vacuum switch,identical to a S/A 2-speed. It's marked "Wet/Dry pavement",instead of "Hi/Lo". The rear axle is "free",on the "Dry Pavement" setting,and is engaged when shifted to "Wet Pavement". I believe top-speed of 35 M.P.H.,is recommended (by Mfr).,for axle-inter-lock. Power is supplied by a driveshaft that sets at an angle,from the transfer case,ABOVE the front drive axle,to the rear axle. http://s1181.photobucket.com/user/willybickey/media/7-3-2013/MOV00219.mp4.html?sort=3&o=1

I know that there's no reference here to fire departments using former oil delivery trucks/tanks as tankers, but some learned the hard way that it was the wrong decision to do so, given that water weighs more than oil. The fact that "x" gallons can be hauled doesn't always mean it's appropriate to do so. The truck pictured is the first I've seen with tandems for a tank stated to be in the 500+-gallon range. Trucks of earlier and later vintage were/are used with tank capacities upwards of 1000 gallons. Tandems come into the picture nowadays when 1500 gallons+ is approached.

The setup that Willy's video pictures is what I described in my earlier post. It could well be a 400 series. The vacuum device on the power divider lock. They work much like a transfer case. Instead of having differential action between the two axles like Rockwell and later Eaton as well, it was only locked in for extra traction. I'm not sure that anyone beside GMC and Chev a little later used this setup. Ford and IHC was already offering the Rockwell SLHD which was used into the 80's.

At 22,000, these tandems added very little to weight carrying capacity. 20,000 is now carried on a single axle.

Water weighs about 8 1/3 lbs per gallon, The high sulfur Diesel we had up until a few years ago weighed 7 1/2 lbs to the gallon. The Ultra Low Sulfur we have today weighs about 1/4 lb. less per gallon. Todays single axle tank wagons are built to around 2,400 gallons.

My point is, the tandem at 22k provided very little extra weight carrying capacity. I think the main purpose was the walking beam suspension for rollover protection and the screw for extra traction. This is why I would really be surprised if this thing had a drag axle.

I don't have my books in front of me, but say a 2-ton Art Deco has a 16,000 GVW. In the fire service, at least back in the '50s, water & tank were considered together at 10 lbs. per gallon, so a 500 gallon tank is 5000 lbs. Add maybe 1500 lbs. for 1000 feet of hose (back then, hose was heavier, I'm guesstimating 75 lbs./50-foot section).

Then, the fire body/running boards, sheet metal and wood in the hose bed - what, maybe 1500 lbs? And a 500-gpm pump is gonna run north of 500 lbs.

Add 500 lbs. of extra equipment for good measure (ladders, appliances, maybe a portable pump or generator).

I get around 9000 lbs.

So what is the weight of a 6400 cab & chassis? Is it 7000 lbs.?

To Crenwelge's point, a tandem axle also works against itself by adding a lot more weight, yes? I wonder if weight-over-the-axle also plays a role. In that era, you can't fit much more tank on a single axle, I would think. A taller tank lessens stability, so you'd probably rather make it longer, which pushes the weight further aft.

Get's sorta interesting. And they still wrestle with it. Had a fire truck flip here in Missouri a couple months back. Think it was a Pierce Tandem.

-Michael

Mike
You are way over my head on facts and I can learn from you.
The GMC 9500 we have has a 500 gallon tank, mid frame pump and a 65' hydrolic steel airiel ladder with out riggers.
I think its rated for 22,000 gvw. And it is pushing that.
Single axle duelie, not to forget the huge V-8 powering the rig.
When I bought it, I told them I did not want the water or all the hose that came with it. Probably dropped about 3,000 Lbs there.
Also, I may stop by your club house tomorrow, for a short visit if anyone is there.

http://www.gatewayfirestlouis.com/

Don

Not sure if I am understanding you correctly, but your GMC 9500 Single Axle should have a GVW of about 30 to 35,000 Lbs.

Bill

Bill
I'll check the tag and get back to you.

Don

My 1957 Chevrolet 10500 has a 500 gpm mid shaft pump, a pto driven high pressure fog pump, a 500 gal tank, 2 booster reels and it weighs in at 14,200 pounds with no hose or water. GVW is 22,000.

The only reason I can think of for the duallies on that small of a chassis is for the added traction and stopping power. Maybe it served in a hilly area

Mike B

Bill, You are right!
I just got back from a dog walk and to put wood in the furnace.
Our 9500 GVW is rated at 31,000#.
The Lafrance, I also looked at, (with a flashlight) and could not find a tag saying what it was rated for.
I did notice how poorly the Lafrance cab is made, compared to the GMC.

Thanks for the correction.
Don

Don,

I would say that your truck has most likely 9 Fronts and 22 Rears (equaling the 31,000).

Bill

Bill
Now you lost me again.
9 Fronts and 22 Rears?
Are you talking leaf springs? Or something else?
My inquiring mind has to know.
Guess I'll go for another dog walk and start counting, before it gets dark this time.
Also, I'll take a flashlight, just to get back to the house.
And will get back to you.

Hopefully this link will work and give you an idea of what it is.
http://s893.photobucket.com/user/2-...mp;_suid=1423956816875044438393213065497

Don


Don

Those figures are the nominal capacities of the axles. 9k for the steering and 22k for the drive. The tandem fire truck pictured doesn't have anything near a 9k steering axle. It is possibly a 7k, but probably a 4.5 axle. In those days, steering axles weren't loaded very heavily.

Thanks Cren for the explination.
I,m new to these bigger big bolts and have a lot to learn.
That's why I check in here daily, to learn.

Don

Crenwelge,

Tandem ??

Don's truck is a Single Axle.

Bill

The original post to this thread shows a fire truck with a tandem. There is still a question as to whether it is a full tandem or a a drag axle added by the fire apparatus manufacturer.

I am very familiar with the series of truck Don's ladder truck is built on. I used one just like it for a yard truck about 20 years ago. It is the little white tractor kinda in the middle of the photo.

https://plus.google.com/photos/1081...5670774498&oid=108197707187186692269

I sold it for scrap iron no long after the photo when I bought a yard truck with a 53 series Detroit. I wish I would have kept the components and just crushed the cab. I could use the axles with air on a couple of old fire trucks I am making truck tractors out of.

Yeah, we got off subject a little and kind of "Hi-Jacked" the thread.

Bill

I just noticed this thread. Don't look in the Fire Truck section much. What's interesting about this truck is, it has the fenders of a 400, 450, or 470 series GMC, but has 5 lug front, & 10 lug rear small lug studs, as the 300, & 350 series trucks do. Also that front bumper looks Factory, but wraps around the fenders more than usual. I'm curious as to what series this actually is ? If it is a 400, 450, or 470, I'd guess that it's a live tandem. That's a cool truck.

Here's a tandem G.M.C. car hauler,about the same year. I'm sure it has the "Wet Pavement" set-up,as well. I like the load,too! https://s-media-cache-ak0.pinimg.com/736x/0a/61/c5/0a61c5d763c70f88f72c3986f1a19c35.jpg

So, Tri-5, any news on this truck? It definitely needs to be saved. Sure would be a show stopper if it was restored. Along with the others here, I would be interested in hearing the particulars of the drive line.
Cool looking rig for sure.

I did buy it and I'm waiting for a day have it towed home. It turns over and should be easy to get fired up, it's just easier for me to work on it at home. I'm guessing the rear axle is military. It does have an inter axle lock and i was told it was a heck of a hill climber. Had to bug bomb the cab for wasps so haven't looked around in there much. It is a 5 window and has the 302 engine with 5K miles. Should be towing it within the week so I'll keep you posted.

If that truck is at least a 400 series, there will be a "GMC Parts Identification" plate on the back of the glove box lid, with all the trucks vitals. Engine size, type transmission, type rear axle etc. GMC's were available with live tandems new off the assembly line. Chevy trucks had no assembly line tandems until 1956.

Serial number W454 30 2742 and it does have the plate in the glovebox. 450 series then?

Spanky,I doubt if that one has a live tandem set-up. Not until after '56?? The rear axle was designed to engage,only on wet/icy/muddy conditions,could not be engaged unless parked,and 35 M.P.H. was top speed with both axles inter-locked. I took a video of a similar tandem G.M.C. Look at that for a reference. http://s1181.photobucket.com/user/willybickey/media/7-3-2013/MOV00219.mp4.html?sort=3&o=1

A W 454-30 would be a 450 series with a 179" wheel base. The W denotes a tandem which leads me to believe it was a 22M Eaton which was offered in 1952-53.

https://plus.google.com/photos/1081...1047462050&oid=108197707187186692269

I am still confused by the steering axle. I wasn't aware that this axle was offered in the 450 series.

https://www.facebook.com/photo.php?...&type=1&theater&notif_t=like

Got her home today

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Mike B