Coil spring swap... updated with results

I'm lowering my '84 D350 Crew- not ground-scraping low, just enough that it doesn't look stock. I already modified the rear spring hanger to lower the rear about 2 to 2-1/2 inches, and I plan on relocating the front hanger for an additional inch.

On the front springs I've been doing some investigating.
The Moog stock HD D350 spring shows these specs:
.90 bar diameter / 13.13 installed height / 1725 lbs / 1144lbs-inch.
The Moog #7170 stock D250 spring shows these specs:
.810 bar diameter / 10.5 installed height / 1815 lbs / 845 lbs-inch.

From these measurements I''m assuming I'll get a more comfortable ride, and I should end up with just over 2-1/2 inch drop just from the difference in installed height (my D350 has pocketed lower control arms), and approximately one more inch additional drop due to the difference in spring rate, for a total of about 3-1/2 inches.

I don't have much experience with this sort of thing, and just thought I would get opinions from folks who may have done something similar. Weird that the total capacity of each D250 spring is rated 90 lbs. higher than each D350 spring...

I moved the hangers up on the frame in the rear & cut a coil and a half in the front
Rode fine no problems
I used a 31" tire in the rear & a 29" tire in the front to level it plus the 31" tire killed some of the 4.10's My OD did the rest

Thanks Bob!

I also went for a little stagger on the tires, 245s front and 265s rear.

I already ordered those D250 springs, Jegs had them for $72 a pair with free shipping. I'll keep the old ones in case I ever want to take it back to stock. I should be able to use a stock replacement D250 shock and maintain ride quality just as good as an OEM set up... hopefully.

I'll let you know how it turns out!

Which D250 did you order them for? There are two different heights

The shorter one. It should basically have the same effect as installing a pocketed lower control arm on a half ton, or on a 3/4 ton without the 4000 lb front end.

Cool stuff....thanks for sharing. Hey......please post pictures....

Okay, for better or worse - this is what happened.

Here are the new and old coil side-by-side....



The result was a little more drop than I anticipated. When I finished it was resting on the bump stops. I trimmed them an inch and it was no longer resting on them. I like the look, but for all practical purposes it is a little too low.



I have two options now - First I'm gonna try a spring rubber to raise it 1 to 1-1/2" and I'll see if the ride is decent. If that doesn't work I'll cut the stock springs and reinstall them.



Could be that my truck squatted more than a single-cab D350 would have. I'm sure the bigger frame and extra weight of the cab adds quite a few pounds.

I guess life is a learning experience - sometimes we learn what NOT to do! LOL! Just thought I'd let everyone know how it turned out.

just so you know..if you put that d350 spring in a 1/2 ton NON-pocket LCA you get lift and rest on the rubber bumpers with control arms at full droop. opposite your drop..LOL!

I drove the stepside off road like that about a yr, then noticed it ripping the LCA mount off the rivits/frame.

you could get a non-pocket LCA arm with that new 1/2 ton spring to gain a inch or so back maybe. the weight is going to help level it out with this idea.

Pretty sure I'm just going to cut a coil out of the old springs, and reinstall them along with D350 shocks.

If anyone needs a brand new set of D250 non-pocket LCA coil springs and shocks, PM me and I'll make you a good deal! LOL!

Ya might want to start at 1/2 coil and check ride height.. my bro got carried away and found out u cant add spring back!

My 02cents
V10

FWIW it sits like our old D100 which ended up with less than an inch of clearance once we cut the bump stops down and it rode and drove awesome once aligned properly

Rickster

I only trimmed about an inch from the bump stops - you removed yours completely?

When you cut a coil does it make the spring rate stiffer or is it the same as before. The reason I ask is I have a D50 with a V8 that I want to lower some in the front and it also needs to be a little stiffer. I have not seen any springs except stock.

Cutting active coils on a coil spring increases the spring rate. Think of a coil spring as a torsion bar that's been wrapped around a cylinder.

R.

Does that mean that if I cut maybe a half a coil off it will lower it and be a little stiffer in the front also ?

Yes

Well, I took the light-duty D250 stuff out and cut my D350 springs 1-1/4 coils. It was STILL too low! So I got another used set of D350 coils, cut them 3/4 of a coil, and ended up right where I wanted it to be.

The bottom pic was last summer, top pic was tonight. With the relocated rear leaf shackle mount I ended up about 3" lower, front and rear. I also swapped on the brackets and new later-model bumper today.

Ride doesn't seem much different, it ain't no New Yorker! LOL!

I like it!

That is a good lookin truck. I like the ride height.

Awesome

A little bit better pics...

Hey are you running a front sway bar on this? Couldn't talk in to some pictures of it can I? Thanks. Also if you don't mind what size tires are those?

Yeah, the front sway bar is still on it.

Those are 245/75/R16 fronts and 265/75/R16 rears, E-rated.

You want pics of the sway bar?

Thanks

Sorry I would like some pics of the front end...if ya don't mind.