School me on 63" Chevy springs (1 Viewer)

[ntsqd]

Note that I mis-spoke myself. I've corrected my original post as I used the longest 4 leaves, not the longest 3 leaves under the Mini.

With their shallow arch the GM's are designed to be SOA. That is the way that they are set-up on the donor trucks. I suspect that it might be possible to run them SUA on a 60, but you're gonna have some hangy-down parts. They are SOA normally on the Mini's, which is why they work so well on those trucks.
I'd make a ton of measurements before committing.

 

[Spook50]

Note that I mis-spoke myself. I've corrected my original post as I used the longest 4 leaves, not the longest 3 leaves under the Mini.

With their shallow arch the GM's are designed to be SOA. That is the way that they are set-up on the donor trucks. I suspect that it might be possible to run them SUA on a 60, but you're gonna have some hangy-down parts. They are SOA normally on the Mini's, which is why they work so well on those trucks.
I'd make a ton of measurements before committing.

Hmmm, didn't realize they're normally SOA. Maybe that'll be a good option to go with a fairly low SOA, which I could always lift later on. I don't want to go with a fairly high SOA at this point because I don't want to spend the money on larger wheels and tires yet.

 

[Cruiserdrew]

Spook-Some info I learned that you may find useful:

Chevy 63s are really nice springs. Despite what the Pirate article says, any Chevy rears after 1988 will work. The post 1998 springs have a bit more spring rate to them and are in my book, desirable.

You will want springs off a 3/4 ton truck. The 1/2 ton springs are too light for the heavy ass end of a 60. Remember the FAQ on Pirate is for Minitrucks.

Personally, I would look for new take offs from a Chevy 2500 HD. It will have 4 thick leaves and a very stout overload for 5 total. The newer the better for less rust. Also the leaves in the later springs look a bit thicker. Go by the truck rating from the donor and you'll be OK. The Pirate article says to pay no more than $100 for a pair, but I found a new set off a 2009 2500 HD for $175 and thought it was worth it.

You will need new spring hangers and shackle hangers. Keep your axle in the same spot or back 1/2 inch or so.

You will need new shackles-I used 5 inchers to minimize lift, most use 6 inch shackles.

RuffStuff makes a swap kit that is a good deal for the $$. You get the hangers and the shackles.

63" Chevy Spring Swap [63swp] - $120.00

Use the Chevy busings already in the springs if they are in good shape. They are very high quality rubber and will last longer and flex with more comfort than any poly replacement.

With the 3/4 ton post 98 springs, the front bushing eye is 5/8 inch and the rear 9/16. All 88-98 are 9/16 at both ends as are 98+ half ton springs. Anyway the later springs have a marginally stronger attachment.

They are really 64 inch springs-measured along the spring. Chevy calls them 64 inch springs. Minitruck guys call them 63 inch springs which is the eye to eye measurement.

Chevy springs are 2.5 inches wide(Cruiser FJ60 are 2.75 wide), but wider at the bushing sleeve. You will likely need a different spring plate/perch to keep the u-bolts close to the springs.

I have been super happy with this swap. Better flex, better load carrying, and better comfort . Good luck with your swap.


edit: While mine is SOA, I have seen them used SUA and it works really well. You need to flip the spring pin and figure out a retaining plate. Works fine.

 

[OPUS1]

So a coupe of questions re this idea (which seems like a good one):

if the springs are 16 inches longer and the front mount is moved forward to accommodate the extra length does that then mean that the axle will sit back 8 inches from the original center of the spring pack to be properly positioned relative to the body?
if so, i assume that a new hole in the spring will be required to mate to the pin in the base plate for alignment and fastening of axle to spring pack

 

[Cruisified]

how much longer are the rears than fronts? is it a straight swap? I've got long ext shackles up front and icky angles, could this solve my problem without moving the mount?

 

[Spook50]

Spook-Some info I learned that you may find useful:

<snip for space>

Awesome, that is a TON of info that'll help me out. I'd like to stay SUA if possible for now, so hopefully the RuffStuff kit will help me retain my current ride height. The real challenge it looks like (as far as swapping my rear springs) will be figuring out where to aquisition spring perches and plates that'll match up to that width. I wonder if I could just make some stainless steel spacers to keep the springs centered. With only 1/4" difference, a piece of 1/8" plate on each side, tacked to the axle housing would probably work.....

Cruisified, OEM rears are considerably longer than OEM fronts. If they're beefed up right so they can handle the weight of the front end, they'd be a great swap, but definitely one that would take a bit of work. I'm hoping to go ahead and do a SR when I get around to putting my OEM rears on the front. I know I'd have to cut & turn the axle again when I eventually go SOA, but I'll get a junked axle housing at that put and just C&T that so it's ready to bolt in when I DO get around to an SOA.

 

[ntsqd]

Perhaps I should take corner weights for both my Mini and my 60? I'm thinking that the Mini will be lighter on the rear axle, but with a tall shell that has glass windows that it won't be hugely lighter than the 60.

With the relative weights and some measurements for where the 3 points of interest on the springs are I'd think that you could approximate how they'll fit SUA on a 60.

Opus, the spring center pin is kept in the same location as stock (unless deliberately moving the axle fwds or backwards), it is the front hanger and the rear shackle mount that get moved on the frame.

 

[Spook50]

Perhaps I should take corner weights for both my Mini and my 60? I'm thinking that the Mini will be lighter on the rear axle, but with a tall shell that has glass windows that it won't be hugely lighter than the 60.

With the relative weights and some measurements for where the 3 points of interest on the springs are I'd think that you could approximate how they'll fit SUA on a 60.

Opus, the spring center pin is kept in the same location as stock (unless deliberately moving the axle fwds or backwards), it is the front hanger and the rear shackle mount that get moved on the frame.

That'd be a huge help too. I would bet that with your canopy the minitruck's rear corners wouldn't be too much lighter than a 60's. Throwing some extra weight in the back to figure the exact geometry of the springs would help in figuring out where exactly on the frame I'd need to place the hangers. Your springs are from a post '98 truck right? If yours sits with the shackle at a 45 degree angle when your rear weight is the same as a 60's, that'll tell me the distance apart to attach the spring and shackle hangers. Hopefully being SOA on your minitruck Vs. my 62's SUA won't make a difference in the geometry of the springs themselves.

I'm thinking now that if I can get away with out without any serious cutting, it'd be great if I could move my rear axle back an inch or two. I really don't want to butcher the sheet metal though.

Edit: Just did some searching around and one of the local wreckers (who pulls the parts for you, yay) has a 5-leaf pair from a '99 2500 Silverado HD for $94. NIIIICE

 

[Wile E Coyote]

I personally would not increase the wheelbase any further unless it was necessary for some other need. The turning radius isn't great as it sits.

I also would not transfer measurements from one truck and use them on yours without extensive verification.
Find and mark the axle center line as it sits right now. Make the mark on the frame AND record an exact distance from some unmoving part for both sided of the frame and axle. This is where the center pin of the new springs will go. If you were to decide to go ahead and mod your wheelbase you'd work off these marks, of course.
Measure the length along the arch from each spring eye to the center pin. These measurements would be where the hangers would be placed relative to the previously marked axle center line.

 

[Spook50]

I personally would not increase the wheelbase any further unless it was necessary for some other need. The turning radius isn't great as it sits.

I also would not transfer measurements from one truck and use them on yours without extensive verification.
Find and mark the axle center line as it sits right now. Make the mark on the frame AND record an exact distance from some unmoving part for both sided of the frame and axle. This is where your center pin will go.
Measure the length along the arch from each spring eye to the center pin. These measurements would be where the hangers would be placed relative to the previously marked axle center line.

Good point on the wheelbase. Okay that's something I won't worry about then.
When you say to find and mark the axle centerline, do you mean the spot on the frame 90 degrees straight up from the axle's center, as it sits with the suspension loaded?

 

[Wile E Coyote]

Yep. I used homemade plumb bobs. It may not be helpful, but see my recent thread where I used JY S-10/Blazer springs up front, and Ford f-150 springs out back. Some of the pics should illustrate my point better.

 

[ntsqd]

With wheel weights we would know how the two trucks compare in that regard. Height above flat ground for the perch and the center of each spring eye bolt will give an idea of what the loaded arc of the spring is. If I repeated the measurements after adding some known mass to the bed of the truck placed directly over the rear axle we would have two points from which to get a rough idea of the spring rate. From there you can make an educated estimate of where the mounts will need to be under a 60.

I have no idea what vintage these springs are. They are take-offs that a friend had at his 4x4 shop business. If the thickness of the leaves is the primary difference in the vintages then it should be simple to figure out if pre or post just from my measuring a leaf or two. I would assume that they are post '98 parts as it was 2005 or 2006 that I did that mod.

 

[ntsqd]

Attached is a picture of the tool that I used to get the wheel weights. It works by reading the torque wrench when pushing down on it while something under the tire (in this case the black cardboard on the left) is pulled out. When the cardboard moves you note the reading on the wrench and multiply it by the lever's ratio. In this setting the lever has a ratio of 44.5"/3.75" = 11.866667:1

I took corner weights on both the Mini (laden and unladen) and the FJ60. For the added weight in the Mini I used a rectangular plastic bin that was labeled to hold 14 gallons. This was centered over the rear axle and rotated with the bin's long side across the width of the truck bed. At 8 lbs. per gallon that is 112 lbs., but it is not graduated so I filled it within ~1/2" of it's top. My bathroom scale says it weighs ~130 lbs. when filled like that, but the weight isn't quite centered on the scale so it is probably reading low.

Some numbers:
Front spring eye bolt center; Top of spring @ front of perch; Rear lower shackle bolt center; Wheel Weight
Unladen Mini: 16.5"; 16.25"; 21.5"; 1186 lbs
Laden Mini: 16.313"; 16.188"; 21.125"; 1276 lbs

FJ60 rear wheel weight (no engine): 1424 lbs

Given the single operator performing both tasks I would expect a wrenching reading error of +/- about 2.5 lbs. which works out to a weight error of about +/- 30 lbs.

 

[Wile E Coyote]

Sweetly simple setup. I'd had that described to me years ago, but couldn't appreciate how it all looked. Thanks for taking the time to throw that together.

 

[Spook50]

Wow, I never would've thought to go with a setup like that to check wheel weight. It's so easy to over analyze how to do it that the simple method slips right by. Hopefully with Chad's and Brittain's help I can get my 62 all set up and have an "ideal" SUA suspension for 60 series Cruisers.

 

[ntsqd]

If we were road racing these things that tool will only get us into the ball-park. We'd really need a set of scales to do an accurate job of adjusting corner weights. But for what we need here it's more than good enough.

 

[Spook50]

If we were road racing these things that tool will only get us into the ball-park. We'd really need a set of scales to do an accurate job of adjusting corner weights. But for what we need here it's more than good enough.

LOL, the closest I get to road racing my 62 is telling a s***-talking ricer that I'd be happy to drag him...............with my logging chain.

 

[Spook50]

Just as a thought, would it b0rk up my suspension geometry if I SOA'd the rear springs and left the fronts SUA for now to accomodate for the spring height difference?

 

[ntsqd]

MISF' Scout is set up that way. Custom Nationals SUA up front and a hybrid Scout + gawd knows what pack that is SOA in the rear.

 

[IrollwithTojo]

LOL, the closest I get to road racing my 62 is telling a ****-talking ricer that I'd be happy to drag him...............with my logging chain.