Has anyone installed superduty springs on their highboy?

[mlheppl]

I'm considering doing this swap and would like some input/info on this swap. From what I understand, aside from the springs, I will need longer shackles for the rear mount. I believe that I read that 5 3/8" center of bolt hole to center of bolt hole is the length required. Looking at General spring's information on the springs, I get the measurement for center of axle mount to spring mount lengths, but not the height o the arch. They have 4 sets of springs listed for the 99-04 superduty. 1800#, 2230#, 2630# and 3950# rated springs. It's just an assumption, but I would assume that each spring has a different arch height, to accomodate the different engine configurations on the superduty trucks.

What I don't know is how much lift if any would the various springs would provide in a bump highboy. My stock springs have 5 3/4" of arch with the front end sitting under the bare frame (no motor or tranny).

Aside from the longer rear shackles and likely new u-bolts, what other modifications are required to do this swap? Any info would be much appreciated. Also if you've done this swap are you happy with it?
Thanks, Mike.

[fordman]

leaf spring width is going to be your enemy too.

[mlheppl]

Spring width should be OK as they're both 3" wide springs.
IIRC I think someone mentioned that using these springs would shorten the wheelbase a little. Will the yoke take up the slack or will the driveshaft have to be shortened?
The stock springs have an A dimension of 26" and B dimension of 27.5". Superduty springs have an A dimension of 27.5" and B dimension of 28.5".

[averagef250]

The individuals I have met who've used the 99-04 springs have used 8"+ lift springs, not the stock height springs. The given superduty lift height is a couple inches shy of reality for a highboy i.e. 8" superduty springs equate to more like 5-6" of lift on a highboy. So that considered my bet is on stock height superduty springs sitting 2" lower than stock height highboy springs.

If I were going to take a blind chance on it I'd buy the heaviest GVW springs knowing I could remove a leaf to lighten them up.

[mlheppl]

Thanks Dustin. I'll call general spring and see if they can give me the arch dimensions on the various springs and that plus your info should give me the info I need. Any thoughts on the shorter wheelbase vs driveshaft length issue. I'm not looking to add a lot of lift to the truck. Maybe a couple of inches if that. I'll likely go with 33" but possibly 35" tires when I get that far.

[mlheppl]

OK, I called General spring and got some information from them.

2430# spring has 5 1/8" arch (btw this spring is not listed on their website)
2630# spring has 4 7/8" arch
3950# spring also has 4 7/8" arch

I asked about where the springs are made and the guy says that the superduty springs are made in the US.

[mlheppl]

To go with the SD springs, do I need to modify my front spring hanger or fabricate new ones? Or will mounting them in the stock location work?

Also as a side note, the length of the rear shackle mount should be 5 3/4" not 5 3/8" as I previously posted.

If I were going to take a blind chance on it I'd buy the heaviest GVW springs knowing I could remove a leaf to lighten them up.

This seems like a pretty good option for me as I've got a 99 SD with the 7.3 in it. If the height doesn't look good, then I'll put the new springs in the 99 at some point.

[frankensteined_67]

instead of modifying your truck you could order new spring with the different spring rate. i did this to my project. got 8" lift and different spring rate so the ride was smother. i ordered mine from http://www.alcanspring.com/ there nice ppl and i love my sprinsg. all i did was tell them the year make model and what i was going to put in the bed and tow, also i told them to make them ride smother than stock. no modifying just bolted them on. they even came with new bushings.

[mlheppl]

instead of modifying your truck you could order new spring with the different spring rate. i did this to my project. got 8" lift and different spring rate so the ride was smother. i ordered mine from http://www.alcanspring.com/ there nice ppl and i love my sprinsg. all i did was tell them the year make model and what i was going to put in the bed and tow, also i told them to make them ride smother than stock. no modifying just bolted them on. they even came with new bushings.

I'm no expert on this, only going on what I've read. There are 2 real advantages to doing this swap. 1st is spring geometry. The superduty springs are longer and the shackle angle is better. This aides is suspension travel. The 2nd advantage is improvements in springs in general over the last 40 years or so. Modern springs will outperform the older springs. Getting new springs like you have done is definitely an improvement. You get the benefit of modern spring technology and metalurgy, however this still doesn't address issue number 1.

As I see it, there are 3or 4 options.
1. re-arch the springs.
2. as you mentioned buy new springs with stock dimensions. I can get a set of replacement spring from General spring for like $420 delivered.
3.Get a set of skyjacker springs in 2-4" lift. These cost $550 or so.
4. Go the SD spring route. I can get a set of SD springs delivered for $375

To me the SD setup seems to make the most sense both functionally and financially.

[averagef250]

I don't think the spring technology has changed much since highboys were new. The science behind leaf springs was set in stone in the 1950's. The biggest advances in leaf spring technology have been in antifriction materials used between leafs for a better ride with higher rate springs.

IMO a tight highboy rides much better than a 99-04 super duty. The 4" skyjacker springs work well and are proven.