Did you previously discuss why you were going from a 3" wide spring to a 2.5" wide spring?
I've always heard that longer, flatter AND wider were better for leaf spring load capacity and ride quality.
Got some other reasons for going this route? Maybe just simple availability and price? Or is the narrow pack easier to package on your truck?

Thanks

paul

 

Hey Paul,
I originally went from the stock 2.25" width leaves to $50 1500 'chevy 63' that is 2.5 wide, 3" including bushing. The cheby 63 is longer, hence more flex. Then I put in junkyard 2500 springs, but they are flat and shackle is in compression (for more lift).

I have recently done some research on leaf springs, and the few experts I have spoken all said more arch, tension shackle. Flat springs want to return to flat and may oscillate.. Arch wants to go back to arch.
Tension shackle make load capacity go up as spring compresses. Comp shackle decreases effective spring rate with compression, which is not what I want.

 

Great explanation on the springs Justin.

 

Yes, thanks. There’s surely been a lot more learned since I was paying closer attention.

 

And part of my problem was that even with’72 in the title, I was still thinking’73 and later most of which had 3” springs already.
Silly wabbit…🙄

 

So your saying I should get a 73 also?

 

Sure why not add to the collection

Those spring hangers look amazing! The factory "pro" made hangers I bought from DJM didn't look any better. Nice job!

 

Some day I'll have a dent of some type. Maybe another bronco.

Thanks. This was 1st big project with plasma table. I have not taken the time to understand the nuances and dial in the machine yet, so it cuts with a bevel and all the pieces need cleanup and a fair amount of fit-up. That and my welding isn't the best. On top of that my welder was sputtering and it took awhile to figure out that the drive tension was way low, got bumped swapping out the spool gun for aluminum. Overall I am happy with result and the pieces are super strong while being made of thinner material (3/16).

 

Ah, so really its only affecting how quickly the motor revs.

This is a MAD PORTER spec motor? What do you think the output is? Would you do anything different to the motor?

 

Yes the motor is a copy of map porter's 87 octane lower RPM truck application, 425 hp / 525 tq plus some nitrous.

I wouldn't change anything, it is a great fit. If I had unlimited funds I would have done an AFR headed 545.

 

Ended up not traveling this weekend and got some extra shop time. So on to the rear spring swap!

Starting point, rev 2.3. Old worn out 2500 4 leaf packs, tuned 12" Fox 2.0, large bump stop.
The problem: worn out flat springs, compression shackle. rear bottoms out on bump stops too easily.

The fix: +7 arch spring, 10 leaf, Mil wrap. new rear hanger and shackles for tension setup. Quite a different in free arch


Cut off the old hangers. No fun working right next to fuel tank with sparks and arcs.
Cut perches off axle tubes as they needed to be at a different angle. The traction bar maintained the pinion angle of 11*.

But how to mount the new shackle hanger? Rear of 72 2WD frame tapers down to 4" of height, and hangers are taller, maybe for '73+ F100. Started to fiddle with some type of extension/support. Was digging through my stash of flat stock and realized I have a plasma table so no constraints, hand cuts or holes to drill.
Created a 360 sketch and NC file in under 5 min, with provisions for 4 mounting locations 1" apart. This way I don't have to cut/weld to move shackle position next time. Extends frame down another 2.5, but will have to completely rework bumper mount, which has it's own problems.


Welded the extensions onto the radius of the frame. Plenty of adhesion although not pretty.


On to the other side.


Added some gussets on back side.


Mock-up and test fit. New springs have considerable more droop and now use all the down travel the 12" shock has. Probably got 2-3" more down travel. The pack separates some and shackle is resting on mount, may limit with a strap. See how things work first.


Set truck on the ground to see what ride height would be. Not enough but very close to estimation. I planned on needing a 1" block so I could adjust down if needed.


Went through my stash of blocks and found a 2". Popped it in, a bit high but springs will settle, so plan to test drive and tune from there. Bump stops will have to be revisited.

 

Continued to prep for test drive on new springs. Torqued the u bolts, it holds the pack together tighter and reduced the shackle angle. Pack still separates a bit but not too bad.





Access to hanger bolt constrained the frame extension, but ended up in same size as bumper bracket.





Started on bumper modifications so I can test drive. Shortened mounts to fit with shackle hangers, and removed the horizontal attachment points all together. Having bolts in 2 planes is not ideal for install/remove. Hard to line up, and have to be tightened in a certain order to get subsequent holes to line up. Now there will be 4 bolts per side in one plane, using one existing hole. I drilled most of the holes in the frame and then test fit bumper to center punch the hole locations to bumper. Like most things I have some more improvements for the bumper, but I just slapped it on with half the bolts to get it on the road.

 

Drove the 72 Ford to work and back to let the new springs settle in. Dropped about an inch, so right on target, for now, truck is level.

I also added another 3/8 of preload to front coils for a total of 1". Overall ride height went up 1", as up-travel for better ride at higher speeds. This put me back to the middle of the front shock shaft. The rear bump position is still good as the spring/block stack height ends up the same.

Front; Up 4.25, Down 5.75

Rear; Up 4, Down 7+

Previously up travel was 2.5 front/3 rear so a decent improvement. It no longer bottoms out on the stops and axle can move under control of suspension. That was the goal. Need more miles of different terrain to really see how it performs. It still rides like it has a lot of un-sprung weight. Looks about the same.





I started with no spring pin offset. Flexed out the tire now rubs the rear of the fender a bit. Looks like about a 1/2" forward would correct and allow max tire stuffage.





Next steps are

-Adjust traction bar instant center

-longer limit straps to get another inch of down travel, to 11" total vertical travel (F and R). The high steer arm allowed for this.

-Front sway bar. Need to figure out how to package/mount while clearing everything.



And that should be it for suspension. Can always spend more but to significantly improve would need to start over with better everything. Better to do that on the next one....

 

Back to finishing rear bumper. So much easier to remove and install now.

Some minor trimming for new spring hangers.


Beyond just finishing drilling all the holes I wanted to reinforce the area around the notch for the end of the bed. Really should have been a radius bottom to minimize stress points. Cut out some overlay plates on plasma with no corners, cause why not? Curves are now the same effort as a strait cut.





Spray bomb and done. Eight 1/2" cap screws to secure.

 

Tested out new rear axle position, centered well enough for full stuff, success.
Right side has exhaust interference and need to finish tailpipes.


Shackle angle is decent at full bump. Ride is 12 o'clock full droop is 10 o'clock position



Moved the upper mount of limit straps. I mocked up an adjustable clevis but there is already lots of stuff in that area so kept it simple. New position has one inch of margin before driveshaft/shock limit. Current setup yields about 4.5 up and 5.5 down for a total of 10" of travel. Reset coil over sliders at 1"


Welded a 1/2-13 nut to some DOM tube and ground round to make a threaded weld on mount.



But now the right side strap end will hit the axle side track bar mount. Addition if the 5th hole made bracket too tall, but that position was needed, so I let as-is at the time. To fix properly, needed to add another hole to frame side and cut one off axle.
Designed and cut an extension and an overlay. Then realized the frame bracket was 0.25 not 0.187, so just pushed go button again on 1/4 plate.


mock up to align holes


Back to a three holer again, but put lower hole at 1" space instead of 1.375


But reason I cut frame bracket down is it can hit tie rod at full suspension limit, before body was on to test. Given the restriction of the tire/fenders the bump stops are set to prevent this, so it can be extended to offset shortening the other end.
trimmed bottom as much as possible. paint and done.



And then cut down axle bracket from 5 to 4 and radiused the top and outer edge for max clearance


Now both brackets have similar and ample clearance. Bar at same angle, same handling. Reset bar length to center axle.