Hey guys Derek here, I was wondering I have a 1979 F150, Can i replace the leaf springs with a 3/4 ton leaf spring if they are the same size and all. Im going to be using it to haul hay with a flat bed and i need good suspension back there, any thoughts or do's/donts? What could happen or make it do?

Thanks a bunch

 

I am pretty sure you can just add a leaf to your existing ones. If you can find a good place to put some air bags under there, those could work too. Do you already have the 3/4 ton leafs and know they will fit?

 

Using an add-a-leaf or air bags makes more sense. Springs are not necessarily the limit for your truck. Do you have the 9.75" rear or 8.8"? The 9.75" is rated for 4000 lbs (if I remember correctly), and has a 500 lb safety margin. More weight and you risk breaking your axle at the pumpkin.

 

Yea, that crossed my mind...that's why I thinking stiffening it up some is good, but stay within the bounds of the truck.

 

Im not sure on the rear. The old truck has no suspension shocks and where they hook to the frame it is completely rusted off. I will have to weld new hook ups on both sides. Grandpa used to haul hay and when he did the truck nearly hit the ground. I am going to put a flatbed on and want to have one of those unrollers on the back. I know the susp. shocks will help but didnt know if i needed to up it to the 3/4 or like you said and a leaf. And i dont want it to break the axel at all wouldnt be good

Thanks a bunch guys for the help

 

Your 1979 F-150 likely already has the same springs under the rear as a 1979 F-250 had.

I know my 1977 F-150 has the exact same rear springs as my wife's dad's 1977 F-250 had. I compared many things on the trucks when I got mine and they were the same count, same 3" width, same thickness. His truck had the bigger 1 ton Dana floater rear and bigger brakes and 4.10 gears and 4 spd and leafs up front where mine has coils.

I've hauled as much as 2600 pounds a few times and an even ton (50 X 40 pound bags pellets on pallet so a little over a ton) and under the heaviest of loads, she was "just level", but then I always slid the pallet up forwards and those real heavy loads were stone or 60 bags loaded loose and loaded up front.

The springs you have will haul all that 9" Ford 5 lug axle wants to tote by time you include truck weight .... but one extra long leafe will stiffen it up plenty (need longer center bolt). Likewise a set of air bags or an overload leaf spring kit.

Look close at rear spring hangers, they have been known to weaken from rust (puddled mud / water) and spring come up against the bed floor. Dorman makes replacement frame brackets and hangers, not too bad priced.

Throw too much on that 9" and it may walk the bearing retainer off the axle shaft or just snap.

They'll haul a big load until then, and then it ain''t pretty.

 

Thanks man Ill check into that.