620 leafs with drop blocks vs 720 leafs

[Negative Ghostrider]

Hi. New guy here. I am likely picking up a 74 this week and the owner has put a 3" drop on it with blocks. I'm not planning on doing any frequent heavy hauling, but from my forum lurking I have seen folks mention that the 620 leafs are "soft" and prone to bottoming out under serious load, and have recommended putting in leafs from a 720 because they are stiffer and offer a (~2"?) drop on their own. I'm seeking a comparison/consolidated overview of pros and cons of the 2 configurations for loaded and unloaded driving regarding ride quality and load handling. I don't plan on slamming it but I like the lowered stance and profile. If I have a couple vespas, large appliances, furniture, etc. in the back I don't want to be bottomed out or hitting the tires or something (if I go wider). Can you fine folks please advise? 

[datzenmike]

A 620 does not bottom out when properly loaded. They are rated to carry 1,100 pounds and they do. Soft is a relative term so if you put 1,500 pounds in and overload it you might call it soft.

 

If lowered 3" I wouldn't be using for hauling maximum loads. If this is a work truck you could raise it and put stiffer springs on but then you loose some comfort when not loaded.

 

 

I don't think carrying heavy loads AND lowering are compatible. Bottoming out is more likely when lowered and serious when carrying a load.

 

If lowered or lowering it is prudent to stiffen the springs to reduce suspension travel on bumps and just live with it rather than tearing your exhaust off. Again even with stiffer springs I wouldn't be carrying heavy loads.

[Negative Ghostrider]

Thanks Mike. I wouldn't be doing "heavy" hauling or using this as a dedicated work truck. It's going to be more vintage cruiser/mini truck. At the same time, it's still a truck and will haul more than my hatchback so it will definitely be called upon to move furniture, do home depot runs, etc. I probably won't load it much over half the rated 1100. 2 vespas weigh about 700lbs and I can't imagine ever putting much more than that in the back. I will likely reduce the drop to 2" as well. 

[thisismatt]

Drop spindles are for front spindles, not rear. 720 4x4 leafs are what we use on 521's, not sure about 620's. 

[Negative Ghostrider]

Sorry. I must have been using the wrong terminology. Drop blocks for the rear leafs, then? 

4 minutes ago, thisismatt said:

Drop spindles are for front spindles, not rear. 720 4x4 leafs are what we use on 521's, not sure about 620's. 

 

[wayno]

OK, if the truck has 3 inch drop blocks and you were to remove them and put 720 4X4 leafs in it that would likely raise the back around 1.5", this is just a guess as different trucks have different leafs that are stiffer or what you call softer to start with, the 521 tends to have fairly beefy rear leaf packs, maybe the early 620 is the same so going to 4X4 leafs could be as much as a 2" drop, I do know that 2wd Datsun 720 leafs are softer so when I installed the 4X4 leafs it was only a 1.5" drop and had a firmer ride.

The Datsun 720 4X4 leafs are firmer than the Datsun 720 2wd leafs, so they hold weight better, meaning if I put a thousand pounds on my 2wd truck and it bottoms out, with 4X4 leafs it might not bottom out driven on the same route.

 

As for drop spindles, they are made to fit ball joint front ends of vented rotor front disc brake trucks, they will not fit your 1974 datsun 620 without major modifications, basically you have to re-invent the wheel to fit them to your truck, it is not something I would suggest you do at this time, you should drive your Datsun truck and enjoy it for a while instead, just keep the brakes adjusted properly and don't drive it like you stole it.

[datzenmike]

1 hour ago, Negative Ghostrider said:

Thanks Mike. I wouldn't be doing "heavy" hauling or using this as a dedicated work truck. It's going to be more vintage cruiser/mini truck. At the same time, it's still a truck and will haul more than my hatchback so it will definitely be called upon to move furniture, do home depot runs, etc. I probably won't load it much over half the rated 1100. 2 vespas weigh about 700lbs and I can't imagine ever putting much more than that in the back. I will likely reduce the drop to 2" as well. 

 

Two or three inches of drop is fine carrying 700 pounds. That's well within it's capability on stock springs and the ride will be fine when empty. Drive only on paved roads. An empty truck is already quite stiff but if you can handle more firmness then an extra leaf or replace with 720 springs.

 

The stock '74 620 had a spring rate of 117-280 pounds per inch, obviously the rate varies as weight is added. The 720 4x4 spring is 138-442 pounds per inch so unloaded will be fairly close to the same as the 620 but stiffens quickly on bumps or added loads. The 720 4x4 spring arch is 3.6", the '78 620 is 4.5" so obviously putting 720 leafs on will lower the ride height.

[Negative Ghostrider]

Thanks everyone. This is what I was looking for and y'all came through. Sorry for muddying the waters by saying drop spindles instead of blocks. This is (obviously) my first truck project, much less an older one. 

[klam07]

You might've had a gander at a thread I made about lowering using 720 leaf springs - my main topic was regarding air shocks in the rear,

but I more or less had the exact same question/requirements as you.

 

I've collected all the parts except for the lowering block so I haven't had a chance to try the set up myself, but speaking directly with 2 members on here who have run this set up (720 4x4 rear leafs, 2-3" lowering blocks, and air shocks) I'm willing to wager that this is the best setup for both stance and function.

 

You get the low and decent ride with the air shocks filled to 20~30psi, and when you need the clearance and stiffness in the rear you can air the rear up to whatever works for what you're carrying. For how infrequent it sounds like you'll be loading the truck, the minor inconvenience of airing up the rear sounds like a good trade off.

 

I can find the thread if you are interested. It contains the model of air shock required, as well as the input of the members who have used the set up first hand.

[Negative Ghostrider]

5 minutes ago, klam07 said:

You might've had a gander at a thread I made about lowering using 720 leaf springs - my main topic was regarding air shocks in the rear,

but I more or less had the exact same question/requirements as you.

 

I've collected all the parts except for the lowering block so I haven't had a chance to try the set up myself, but speaking directly with 2 members on here who have run this set up (720 4x4 rear leafs, 2-3" lowering blocks, and air shocks) I'm willing to wager that this is the best setup for both stance and function.

 

You get the low and decent ride with the air shocks filled to 20~30psi, and when you need the clearance and stiffness in the rear you can air the rear up to whatever works for what you're carrying. For how infrequent it sounds like you'll be loading the truck, the minor inconvenience of airing up the rear sounds like a good trade off.

 

I can find the thread if you are interested. It contains the model of air shock required, as well as the input of the members who have used the set up first hand.

Yes please. Air shocks are a pretty foreign concept for me. I think your thread would be very educational. Thanks!

[klam07]

This was my thread (and specifically the post) that answered the question. I am also new to air shocks, so this really helped me out.

https://ratsun.net/topic/76525-air-shocks-question/?do=findComment&comment=1634638

 

This is a follow-up post to one of the members I talked to regarding his set up - and what I based mine off of.

https://ratsun.net/topic/35045-air-shocks/?do=findComment&comment=1657009

 

Give them a full read if you like, but in short, it looks like Monroe MA709 and MA805 max-air shocks will both work, with the MA805 being something like an inch longer uncompressed and compressed (specs can still be found on Monroe's website, just google part number). I ended up ordering MA709, but have yet to put them on. Both have attested that swapping to air shocks and 4x4 leafs made the truck handle much like a car, with the ability to raise the rear when needed.
 

[Negative Ghostrider]

1 hour ago, klam07 said:

This was my thread (and specifically the post) that answered the question. I am also new to air shocks, so this really helped me out.

https://ratsun.net/topic/76525-air-shocks-question/?do=findComment&comment=1634638

 

This is a follow-up post to one of the members I talked to regarding his set up - and what I based mine off of.

https://ratsun.net/topic/35045-air-shocks/?do=findComment&comment=1657009

 

Give them a full read if you like, but in short, it looks like Monroe MA709 and MA805 max-air shocks will both work, with the MA805 being something like an inch longer uncompressed and compressed (specs can still be found on Monroe's website, just google part number). I ended up ordering MA709, but have yet to put them on. Both have attested that swapping to air shocks and 4x4 leafs made the truck handle much like a car, with the ability to raise the rear when needed.
 

This is awesome. Anything I can do to improve ride will be a huge bonus when the wife is in the truck. She's got neck issues and is very sensitive to a choppy ride. Thanks! 

 

Did you do anything to the front suspension as well? Or just running regular shocks, etc? 

[klam07]

For sure, hope it helps.

Other than replacing all of my destroyed ball joints, I plan to change the front shock absorbers for shorter ones - either Pinto or Xterra? I can't recall exactly which works/worked better. Ill cross that road when I get there. Then I'll just lower via torsion bars. I have a 79, so drop spindles are an option but I dont think it'll be necessary. And replace all bump stops with mini/low profile