Nissan 720 4X4 Tired Leaf Springs

[Benannah]

Hey all! For the last year and a half I have been the very proud owner of a 1983 Nissan 720 4X4 Truck. Over the past few months I have noticed that my rear seems to be sagging more and more. This is of course not a huge surprise give the age and the fact I have a fiberglass topper and a wooden bed drawer, but it is an inconvenience none the less.

 

Today I went to look at the arc of my rear leafs only to find that they are now bent almost completely straight. I have been looking at ways to fix this issue, but have not come up with a ton.

 

Please offer any and all advice you may have for dealing with this issue!

 

Some things to consider:

   - I am on a tight budget of $250 as I am a college student

   - This fix must be something a friend and I could pull off in a weekend or maybe two

   - I would still like my truck to have near stock suspension travel as I enjoy light off-roading

   - Quality of ride isn't too awful (but I am not seeking perfection here)

 

*Note - I am open to some wild ideas here as long as they will work! Some ideas I have tossed around so far include replacing the stock springs with those for a trailer (problem I ran into is none of them are long enough), buying shock/coil spring combos to replace my current shocks (unsure if this idea would even work, but I love the idea of it), or even sticking a cheap air suspension bag in parallel with each spring (unsure if it would give me enough suspension travel)

[banzai510(hainz)]

 I am not a 720expert. see if the make that spring shock units. i seen them listed for 510wagons. otherwise get kyb gas a just or the monomax. This be a simple bolt in. Call it good. You dont want to down a vehical on a simple issue and lack of real workspace in case something goes bad. And lack of cash. U live in wisconsin so i dont know the salt usage there if it just rotted out.

Edited December 4, 2025 by banzai510(hainz)

[datzenmike]

Leaf springs can sag over time but they carry the same weight, just lower. If the 4x4 spring was off the vehicle and you held a string across the top ends  through the center of the eyelets and measured down to the spring it's only 3.685". This is known as the free camber. With the unladen weight of the back of the truck on the springs that would be a lot less that that. Go to a spring shop and ask them to re-camper the springs in a press. You would have to remove them and take them in. How long? depends. Pick them up and put back on the next weekend. I doubt it would be $250 if all they do is the bending. After re-arching the springs, nothing will change but the ride height. If you run and an extra spring around the shock absorber it will increase the height but it will also increase the overall stiffness. Off road this will reduce the 'articulation' or suspension travel, which you said you did not want to alter.

 

This just give you an idea of how they do it, or what's involved. The guy who did mine had an electric hydraulic ram and was both easier and way faster. 

 

 

 

What ever you do, do NOT use heat to make the bending easier. The metal is heat treated.

  

[Benannah]

Thank you both for your ideas! I'm really liking the sound of Mike's idea and thought it might be something I could try myself? Here at school I should have access to a hydraulic press and it sounds like that's all I would need? If that is really all there is to it, I am really liking it being free other than time.

 

Does anyone know of a spec I can check for the amount of arch my leaf springs should have when the truck is on the ground? That way I can measure the amount I would need to raise it.

 

Thank again for the help and ideas!

12 hours ago, datzenmike said:

Leaf springs can sag over time but they carry the same weight, just lower. If the 4x4 spring was off the vehicle and you held a string across the top ends  through the center of the eyelets and measured down to the spring it's only 3.685". This is known as the free camber. With the unladen weight of the back of the truck on the springs that would be a lot less that that. Go to a spring shop and ask them to re-camper the springs in a press. You would have to remove them and take them in. How long? depends. Pick them up and put back on the next weekend. I doubt it would be $250 if all they do is the bending. After re-arching the springs, nothing will change but the ride height. If you run and an extra spring around the shock absorber it will increase the height but it will also increase the overall stiffness. Off road this will reduce the 'articulation' or suspension travel, which you said you did not want to alter.

 

This just give you an idea of how they do it, or what's involved. The guy who did mine had an electric hydraulic ram and was both easier and way faster. 

 

 

 

What ever you do, do NOT use heat to make the bending easier. The metal is heat treated.

  

 

[toshts]

While not the best option if you're looking dirt cheap, quick and easy you can throw some helper springs on the bottom in half an hour for like 40$ and regain some height and spring rate. Don't even need to take the leafs out to put em on. Getting the springs redone or getting new ones will be better for sure though. 

[banzai510(hainz)]

7 minutes ago, toshts said:

dirt cheap, quick and easy

Airshocks.

 

its going to bend again

 

dropping that axle is no 5 min job then the holes dont line up

 

 

[Benannah]

Yeah, I totally see your point. I’ve been looking at airbag install kits but I don’t like how they limit travel, but then I discovered air bag cradles. I think the air bag and cradle setup could work well for me, but am not certain the best way to pull it off on a budget.

 

Has anyone ever put air bags and cradles on their Nissan 720? Any tips on how to pull this off?

[Benannah]

I think I would like to pursue adding air bags between the frame and axle. Does anyone have any tips on doing this in a way that preserves ride quality and off-road articulation on a budget?

[datzenmike]

Air bags, helper spring or coil spring over the shock absorber are all going to add stiffness. Which is not all bad if not taken to extremes. It's a 4x4 and those springs are stiffer by far over the 2wd to begin with.  

 

 

 

Summit or OReilly's $50-$100.

 

You want cheap and easy get the helper coils that go over the shock absorber. Disconnect the bottom of the shocks and slip the coils on and bolt shock bottoms back on. Jack up the rear so the differential hangs and slide coils springs up the extended shocks and tighten in place. Let the truck down and see what you have and adjust accordingly. 200-300 pound springs should do, you don't want them too stiff just enough to reduce the load on the leafs and allow the rear to rise up an inch or two. 

[wayno]

I put airbags on my 521 work truck, but I only used them when hauling heavy loads, I let the air out when driving around town, it was just too bouncy when air was in the bags.