Rear Suspension Mod's For Big Blue?

[Gary Lewis]

I did have a considerable amount of my stuff scanned and online, but alas, when the server, your desktop and all three laptops burn you really wish you had of opted not to host things yourself.

The 84+ F250 extended cab 4x4 is essentially identically speced as an 80-85 F350 with a shorter rear block, extended cab of course automatically made it a HD.

I can tell you without a doubt my crew cab F350 does for the most part ride better than my extended cab F250, and the ex cab really doesn't ride much different than my regular cabs did, but the solid axle doesn't handle short sharp bumps and washboard nearly as well as the TTB due to the front shackle setup being designed for the TTB's inverted leafs.

A set of super duty front leafs and a shackle reversal alleviates that problem.

Another option for the rear is to go to 08+ Super Duty springs. They are 8" longer than our stock ones and a longer leaf is going to ride and handle sharp bumps much better.

We won't even talk about how I have my Dodge sprung so soft I had to put the sway bar back on, but it will still bounce you out of the seat on washboard because the 48" long front springs just can't handle it.

I'm happy hosting this forum and the website elsewhere. I do back up my machines routinely, but it would be devastating to lose the website or forum.

I've wondered about doing the shackle reversal on Big Blue, but want to get the rear sorted before I worry about the front. Maybe I'll get to try the rear mod's in a few weeks.

[Nothing Special]

.... I've wondered about doing the shackle reversal on Big Blue, but want to get the rear sorted before I worry about the front. Maybe I'll get to try the rear mod's in a few weeks.

I haven't really heard of anyone doing a shackle reversal on a leaf spring TTB. As I understand it was designed for the solid axle F-350 (which, as 82F100SWB noted, had shackles that were designed for the TTB anyway). And originally the kit manufacturers said that their kits shouldn't be used on TTBs. Later on they started saying that the kits could go with TTB, but no one seems to know what changed that made it now a good idea (speculation I've heard is that what changed is the kit manufacturers desire to increase sales began to outweigh their desire to sell a good product, but that's just internet speculation).

And on a solid axle at least a shackle reversal lifts it about 2". So keep that in mind before swapping if ride height matters to you.

[Gary Lewis]

.... I've wondered about doing the shackle reversal on Big Blue, but want to get the rear sorted before I worry about the front. Maybe I'll get to try the rear mod's in a few weeks.

I haven't really heard of anyone doing a shackle reversal on a leaf spring TTB. As I understand it was designed for the solid axle F-350 (which, as 82F100SWB noted, had shackles that were designed for the TTB anyway). And originally the kit manufacturers said that their kits shouldn't be used on TTBs. Later on they started saying that the kits could go with TTB, but no one seems to know what changed that made it now a good idea (speculation I've heard is that what changed is the kit manufacturers desire to increase sales began to outweigh their desire to sell a good product, but that's just internet speculation).

And on a solid axle at least a shackle reversal lifts it about 2". So keep that in mind before swapping if ride height matters to you.

Interesting. Hadn't heard/seen that they didn't recommend it early on. Maybe I don't want to do it.

But, I wouldn't mind another 2" of height in front - unless my leaf-removal exercise drops the rear quite a bit it is much higher in the rear than the front. But, as noted, I can remove the 2" spacer block in the rear to drop it some if needed for air bags.

[Ford F834]

Interesting. Hadn't heard/seen that they didn't recommend it early on. Maybe I don't want to do it.

But, I wouldn't mind another 2" of height in front - unless my leaf-removal exercise drops the rear quite a bit it is much higher in the rear than the front. But, as noted, I can remove the 2" spacer block in the rear to drop it some if needed for air bags.

My understanding of the RSK is that the monobeam F350 have positive arch leaves. When they flex, they extend in length. With the hinging shackle in front, it has to pivot against the direction of travel (=direction of impact) and results in a harsher ride. Moving the hinged shackle to the rear makes the flex smoother as it pivots with the direction of impact). TTB on the other hand have negative arch springs. When they flex, they shorten in length. This pulls the hinged shackle toward the rear, which is already the correct direction when traveling forward to achieve the best ride. There may be more to it than my simplistic understanding, but I would not do RSK on a TTB. Even if it ~did improve the ride, the lift would need to be compensated by a drop of the beam ends, and the springs are not symmetrical. I wonder how moving the shackle could affect the geometry and alignment of the axles? If I really hated the leaf spring TTB ride, I would probably do a SAS with reverse shackle. Independent suspension with leaf springs is rather self defeating in my opinion, and you would probably get a better ride out of a RSK’d monobeam. That said, I never had any complaints about the ride of my stock F350, and I don’t have any immediate plans to RSK it.

[Gary Lewis]

My understanding of the RSK is that the monobeam F350 have positive arch leaves. When they flex, they extend in length. With the hinging shackle in front, it has to pivot against the direction of travel (=direction of impact) and results in a harsher ride. Moving the hinged shackle to the rear makes the flex smoother as it pivots with the direction of impact). TTB on the other hand have negative arch springs. When they flex, they shorten in length. This pulls the hinged shackle toward the rear, which is already the correct direction when traveling forward to achieve the best ride. There may be more to it than my simplistic understanding, but I would not do RSK on a TTB. Even if it ~did improve the ride, the lift would need to be compensated by a drop of the beam ends, and the springs are not symmetrical. I wonder how moving the shackle could affect the geometry and alignment of the axles? If I really hated the leaf spring TTB ride, I would probably do a SAS with reverse shackle. Independent suspension with leaf springs is rather self defeating in my opinion, and you would probably get a better ride out of a RSK’d monobeam. That said, I never had any complaints about the ride of my stock F350, and I don’t have any immediate plans to RSK it.

Good explanation, Jonathan. Thanks. I'll leave well-enough alone.

[82F100SWB]

Good explanation, Jonathan. Thanks. I'll leave well-enough alone.

Another reason not to change the shackle design on a TTB truck is the stock A frame shackle; which on a solid axle truck defeats the side to side axle locating inherent to a normal leaf spring design and requires a panhard bar, is designed to allow the spring to twist and follow the arc of the axle beam during suspension travel.

I'm not sure how a standard shackle setup would ride with a TTB.

[Gary Lewis]

Another reason not to change the shackle design on a TTB truck is the stock A frame shackle; which on a solid axle truck defeats the side to side axle locating inherent to a normal leaf spring design and requires a panhard bar, is designed to allow the spring to twist and follow the arc of the axle beam during suspension travel.

I'm not sure how a standard shackle setup would ride with a TTB.

I'm sold. It is what it is in the front, and while it is stiff, with the sway bar end link off it doesn't hurt your teeth. Prior to that you saw bumps coming and got prepared.

But the rear, even with that link disconnected, hurts your neck. And a trip to Colorado from here to Ouray, which will be 1700 miles w/o the side trips, doesn't sound like as much fun as it would be with a bit less spring. Plus, the stiffness can't help traction when traversing the mountain backroads.