The Stovebolt Site Forums The Shop Area Engine Shop 51 3/4T Rear Spring ID

My 1951 3/4 ton has these rear springs.

http://i578.photobucket.com/albums/ss227/sahkanaga/Stovebolt%20Images/RearSprings.jpg

I've tried the search feature and looked in the Factory Assembly Manual and the closest thing I can find is the rear springs on 5000-6500 models in Sec 4, Sheet 1.04. However, they appear to have only 5 leaves in the upper spring assembly instead of 7 as mine has.

I'm guessing this is an auxiliary spring since the bracket on the frame is called an "auxiliary spring bracket"in Sec 2, sheet 4.01 (which shows the application as 6100-6400, 6502-5000), but I've had 1800 lbs. in the bed and the upper spring didn't contact the bracket. No telling how much weight you would have to haul for it to do so, and I don't plan to find out!

The Chevrolet specification page in the restoration pack shows an upgrade option for an 8-leaf spring. Both the lower and upper on my truck have 7 leaves.

Is this something that could be ordered on a 3/4 ton, or is it possible I have a frame that is not originally from a 3/4 ton? The wheelbase is correct for a 3/4 ton at 125 1/4 and everything seems to fit properly.

Does anyone else have a 3/4 ton with this arrangement?

My 54 has just a 7 leaf pack. The door badge says it's a 6500lb vehicle, but I don't think my cab was is original to the truck. Usually the 3800's were reserved for the 6500lb rating. You may have some aftermarket overloads, or someone put a spring pack from a 1 ton on your ride.

My 52 GMC 3/4 ton looks to be similar. 7 leaves in the lower set, but only 6 in the upper set.

http://good-times.webshots.com/photo/2884132360090990065JaoGlw

Randy,

It looks like your u-bolts have a little bit more thread showing. I wonder if you had 7 upper leaves at one time.

On a different note, what is that thing on the driver's side running board? Is that what the PTO drives?

Joe, here is an original 1950, 3604 that was ordered with the overload springs. I know that because I talked with the people that maintained the truck from time of purchase new for the original owner and up until I acquired the truck. As you can see it has a seven leaf main and a 7-leaf overload. And no, this option is not listed in the standard Salesman’s Data Book nor can I find a listing for the option anywhere else.
http://www.pbase.com/dennygraham/image/111951573
Denny Graham
Sandwich, IL

Denny,

Thanks for the info. It looks like one more mystery on my truck is solved.

It would be interesting to see just how much weight would have to be loaded to make the overload spring ends touch the auxiliary spring brackets, but I think I'll let someone else do the testing. As I said in the original post, I know 1800 lbs. won't do it although I realize that is only 300 lbs. of overload.

Not sure about that either Joe, my old gal has seen all the hauling that she's ever gonna see as long as I have her, and that should be another 33 years. By then I doubt if we will be able to find any gasoline to use for transportation.
I can say this about my truck, it was bought in 1950 by a small town in Iowa to use as their fire truck. They had a water tank in the back for several decades and it wouldn’t take all that much water to overload a 3/4-ton truck. A 500-gallon oil tank full would tip the scales at around 4,000 lbs and that wouldn’t go to far putting out a fire. I would bet the tank was at least twice that big. I can see signs where the fenders are bolted to the running boards of where the bed has shifted forward some. probably from a sudden stop with water sloshing in the tank.
Denny Graham
Sandwich, IL

Here's the master parts manual listing the 2 stage spring

Looks like the 51 3/4 had 7 or 8 leaves.

Tom,

As I understand it a 2-stage spring doesn't mean that there are two separate spring assemblies. It refers to the design of one spring assembly where the leaves are separated so that the leaves take the load in two stages.

If look at the page you linked, you will see a listing for an auxiliary spring, but it only has six leaves.

If my understanding is wrong, I hope one of the more knowledgeable bolters will chime in.

You are absolutely correct Joe, that is exactly what a two-stage spring is. It gave you a softer ride when lightly loaded and picked up the additional springs in the stack when you were carrying a load.
And your interpretation of the parts book is also correct, there is no seven-leaf overload even though it is commonly seen on the 3/4-ton trucks as an option.
Denny Graham
Sandwich, IL

Joe,

Thanks for helping me understand the difference between a 2-stage spring and the auxiliary spring.
I had no clue.