Lowering the rear on my 521

[wayno]

I think you need to install the stock 4X4 leafs and then measure how much room you have left before the axle starts to hit the frame, you will then not have to bother with removing leafs which all the photo above really is, putting the leaf above the main leaf is removing a leaf as it does nothing that way.

I suspect that with the 4X4 leafs installed with 4 inch drop blocks you will have very little room left between the frame and the axle, these trucks need to have the rear arch notched to get really low, I have done it all over the years, if you really want low, you have to start modifying the frame, "C" notch, flat cross members that don't hang down, 15/16 inch rims with low profile tires just to start, it's a lot of work.

[FunkyFresh520]

Im planning to put 720 4x4 leaf springs on my 520 with 3 in. Blocks. When i do this can i just use the normal struts for the truck? I know when lowering the front u have to raise the strut tower. But for the rear do u have to do that? What struts should i go for when the truck is lowered 3-4 inches all around? I seen somewhere that xterra struts or smthn like that work good? And also do i gotta space out my driveshaft when lowering the truck or anything like that ?

[datzenmike]

Flipped is wrong. The upper leaf does nothing to support the load on it. Last thing you want is a softer spring on a lowered vehicle.

 

Wrong is more correct. Leaf spring  retains it's spring rate but the mounting points are lower. 

[wayno]

You do not want to go any other route except stock, flipped is just removing a leaf as the leaf that was flipped does nothing anymore, it might as well not be there at all, but when one removes a leaf, then it bottoms out way easier which is not what you want, especially when your axle is so close to the frame.

The "wrong" illustration is just stupid, once you sit the rear of the truck back on the ground the frame will be resting on the axle, unlike the illustrations above, all 720 leafs have an arch to them that from the side will look like a smile, if you flip the main leaf over like that you will have a frown, and the ride will be a mega frown, as there will be no suspension in the rear.

Put the 4X4 leafs on the truck with the lowering blocks, if you want to be lower than that, you will have to "C" notch the rear frame, do not remove or relocate any leafs, leave them as they are(stock configuration).

Yes, i removed the bump stops I have some 4x4 720 springs but haven't install them yet. Btw has any one tried this method yet?

[hobospyder]

Make sure the angles on either end of the drives haft at u-joints are the same. If you go down over 3 inches (I think) you have to start angling the rear axle to correct pinion angle. Or block the carrier bearing up. One of the two

[RAT SUN]

Will I need to use the stock shackles when using 4x4 720 leaf springs ?

This are the stock 521 shackles

[datzenmike]

All 521/620/720 leaf springs are the same length 1,200mm, so yes.

[RAT SUN]

Should I replaced my stock bushings or should I just the ones from the 4x4 720?

[FunkyFresh520]

What struts yall recommendend wen lowering 3-4 inches

[Elkie]

Shock mounts stay in the same position with blocks.

[datzenmike]

What struts yall recommendend wen lowering 3-4 inches

 

For a 521 say shocks to be more accurate and less confusing to others. A strut is a supporting member that may also have a shock inside.

 

Probably the stock shock will be fine. The body will hit the bump stops before the shock will bottom out. If notching the frame that a different story.

[FunkyFresh520]

For a 521 say shocks to be more accurate and less confusing to others. A strut is a supporting member that may also have a shock inside.

 

Probably the stock shock will be fine. The body will hit the bump stops before the shock will bottom out. If notching the frame that a different story.

Ok thanx my bad

[spdcrazy]

as for shocks, you can use factory replacement shocks to go as low as the stock frame will let you, no need to source them from any other vehicle.

 

I have my second leaf flipped (and 4in blocks), and like the others have said, its not best, it is a super soft ride however I rarely hit frame.  and the only way I can use the truck as a truck is with the aid of air shocks. Ya might look into them anyway if you plan to use the bed for anything more than a tool box. ya air them up when you towing or hauling a load, and drop the pressure to loose some height if you don't need it, or are at a show. air shocks can be found for about 70 bucks with a quick google search, mine are Monroe brand and made to fit the 521

 

If you want to be my kind of low I would look at c notching or 4 linking like others have said.

[spdcrazy]

also, tire size like has been said. if you go to small, it is a rough ride and your RPM's will be high on the hwy with factory gearing/4spd/and L16-20b. (been there)

 

your 195/55/15 or so will be good tho. I am running the same wheel. with a 195-60 to keep diameter close to factory. however the 55 is a more popular fit I believe.

 

 

 

[flatcat19]

I use 195/65r15 with 3 inch blocks and a couple of leafs removed.

 

The truck above this post...looks lower than mine with fenders pulled.

My tires fit right in the wells without rubbing.

[datzenmike]

Another reason to not remove leaves is that the leaf spring pack also provides the only lateral support for the axle. For example a single leaf will tend to roll over on it's side on a hard corner and/or the axle will shove sideways. The more leaves the more laterally stable.

[spdcrazy]

even more so with blocks I suppose

[datzenmike]

No. The spring is unchanged and therefor unaffected. If the block was a couple of feet tall it would have some leverage.

[wayno]

Another reason to not remove leaves is that the leaf spring pack also provides the only lateral support for the axle. For example a single leaf will tend to roll over on it's side on a hard corner and/or the axle will shove sideways. The more leaves the more laterally stable.

 

I have thought about this, but never heard of an issue from anyone, if there was an issue I suspect there would be a failure or it would be so short of an issue one would hardly notice it, like it would feel funny on a hard corner, fact is I have never heard of a failure from going around a corner or the like.

But I have heard of axle wrap from leafs being removed, and the failure that can occur from it, like what I believe happened to Kevin when he was shifting very hard(slamming gears), the axle can twist so far that it can pull the yoke out of the transmission far enough for it to wobble, it can bust the tail shaft of the transmission resulting in a dramatic and possibly very dangerous failure, I would suspect that those using a one piece (520?) drive line in a 521 are most susceptible to this failure. 

Axle wrap is what it is, it can cause the axle to hop/jump accelerating or decelerating, it can even happen on vehicles with stock leafs(wimpy), that is what traction bars were used for, to stop wheel hop(axle wrap).

[datzenmike]

The 520 was rated at one tonn. I suspect that the later 521 kept the same rear suspension and they simply changed the rating numbers to 1,100 pounds. (could be wrong)

 

The 521 has lots of leaves and is very heavy duty and one or two probably won't be missed. I loaded 1,800 pounds on my '71 and the tires were flattened but the springs only straightened out. Worst case would be a single leaf but any leaves removed moves you closer to sideways shifting.

[wayno]

The thing is that when lowering a 520/521 we tell folks to use 4X4 leafs, and that is what should be done, but they remove leafs out of the 521 suspension which has 5 leafs, one can likely get away with removing one, maybe two of them depending on which ones are being removed, but in the end it doesn't really lower the 520/521 much unless they load the truck up, now they can take the lower flat leaf and put it on top of the pack, but the ride is very stiff, it's like clamping the arched leafs to the flat ones, the ride sucks, I did it as a test, very stiff, like having a 100PSI in a set of overload bags.

Now the 4X4 leafs only have 2 arched leafs, the other two are flat, they are over load leafs, one should not remove any arched leafs from a 4X4 leaf pack, as that only leaves one long leaf, and it likely won't actually lower an unloaded 520/521, but it will likely cut the spring rate almost in half.

Blocks work to a point(4 inch max(3 inch for me), and one will have issues with the lower rear shock mounts with 4 inch blocks), and 4X4 leafs get one another inch and a half lower, five and one half inches basically puts the frame on the axle, if anyone wants to be lower than that, they are going to have to start making major modifications to the frame, which is not easy nor cheap.

When we see someone get their 520/521 low, I mean really low, have you ever noticed that it doesn't happen overnight, it takes time to even do it wrong, and wrong don't last long, it takes even longer to do it right, and the right way is a gray area, as some would not call certain things safe when the owner would call it safe, my opinion of safe is that when one gets a flat while driving on the hiway, nothing hits the ground, I could care less about a vehicle dragging over any speed bump, as the vehicle isn't going 60/70mph over a speed bump.

[FunkyFresh520]

also, tire size like has been said. if you go to small, it is a rough ride and your RPM's will be high on the hwy with factory gearing/4spd/and L16-20b. (been there)

 

your 195/55/15 or so will be good tho. I am running the same wheel. with a 195-60 to keep diameter close to factory. however the 55 is a more popular fit I believe.

 

 

 

I want mine to sit like this! Im planning to roll on some 175/75/15 im going white wall tires .. i have a 520 will the 4x4 720 springs with 3" block get me this low or do i gotta go 4"? Did u have to raise ur shock tower up front?

[spdcrazy]

i did not raise my front shock mounts, although I should, I blew out the top shock mount on the frame. after fixing that I ripped the same front shock in two after that.

 

I couldn't tell you on the 520 but those seem like very small overall diameter tires, I would be worried about rpm's at highway speeds, as well as an incredibly rough ride, but if you are ok with all of this, as well as low ground clearance, I don't see any physical reason your setup wouldn't work, and it'll get ya low.

 

keep in mind my tire tuck is due to my taller tire, if I put your tire size on with my suspension, I probably wouldn't tuck.

[flatcat19]

175/75 is a really tall tire. Even on an 8" wide wheel.

 

Side wall height is 75% of sidewall.

 

 

What wheels do you plan on using?

[spdcrazy]

whoops, you are right flatcat, I think I was thinking 175/55.

 

a 175/75/15 is 25.3in tall

ver my 195/60/15 at 24.2 (which is close to factory)

 

so disregard my comments about it being a short tire.