Drop axle pivots & radius arm bracket for RWD, unicorn or duh?

[ArdWrknTrk]

Jim as the front of the truck rises, the radius arms will swing down to maintain tire contact with the road surface, this has the effect of reducing the caster angle (positive caster is the backwards tilt of the steering axis that helps center the wheels) Camber is the in or out tilt of the steering axis, most vehicles have a slight positive camber which helps in maintaining a good contact patch on the outside front wheel when cornering.

Extreme (somewhat) example. When Shelby set up the front ends on the 1965 GT350s, the upper control arms were lowered 1", and the alignment specs were 2° + caster, 0° camber, the caster + the 3.5 turns lock to lock meant the wheel would return to center with a vengeance if you let go of it. The 0 camber put the front tires straight up and the relocated upper control arms made the outside front tire tilt in under load so it remained vertical with respect to the track surface. This was done for the bias ply race tires of the 60s, put radials on these cars and they were squirrely as all get out.

Sorry.

I admit I've gotten confused between trail and caster.

On a bike raising the headstock angle (increasing rake, or even lengthening the fork) will get you more self centering.

But on a car this geometry is tucked under (caster) placing the wheel centerline behind the steering axis.

 

[85lebaront2]

Sorry.

I admit I've gotten confused between trail and caster.

On a bike raising the headstock angle (increasing rake, or even lengthening the fork) will get you more self centering.

But on a car this geometry is tucked under (caster) placing the wheel centerline behind the steering axis.

Jim, no problem there, I have to go and sometimes sketch something to be sure I am right on the terminology and effects.

A couple more notes, twin traction beam suspension, on an F150, it pretty well behaves like a twin I-beam, but on the F250 and F350 trucks with the twisting leaf springs the caster pretty much stays where it is set, but the camber still reacts like a twin I-beam. Live axles be they a simple beam or a live axle for a 4WD, once they are set up, as long as shims or eccentric bushings are kept in the same location and orientation they generally do not need adjusting.

A few years ago our boy scout camp had a 1987 F250 4WD truck. it was horrible on front tires and a bear to drive on the highway (take your hands off the wheel and it would dive toward the left immediately). I asked a friend who owned an alignment shop for suggestions (the left front wheel was visibly tilted out at the top). He told me how to use a couple of matched 2X4 blocks and a level on a level floor to set the camber. It was way off, took the bushings out to get the numbers and decided to flip the camber (outer) bushing around. Torqued everything and had the ranger back out and pull back in. Recheck, camber was 0° as near as we could measure (level showed wheel vertical). Then it was time for the old string toe-in gauge, truck was toed out about 1/4". I think he had me set it to 1/8" in max, slightly less depending on where I could get the string to. Truck drove like a new one after that.

I had a 1958 F100 that I put a 312 Y-block and Borg-Warner T85/OD 3 speed into in place of the 223 and 3 speed. That lowered the front a bit and I would occasionally get the "death wobble" due to little or no or possibly even a negative caster angle. I was in Pep Boys and saw some 1/2 length helper springs for leaf springs, bought a set, installed them on the back (shackle end) of the front springs, raising the front of the truck and tilting the axle with it's king pins back enough to give me enough positive caster to solve the "death wobble" issue.

[ArdWrknTrk]

Jim, no problem there, I have to go and sometimes sketch something to be sure I am right on the terminology and effects.

A couple more notes, twin traction beam suspension, on an F150, it pretty well behaves like a twin I-beam, but on the F250 and F350 trucks with the twisting leaf springs the caster pretty much stays where it is set, but the camber still reacts like a twin I-beam. Live axles be they a simple beam or a live axle for a 4WD, once they are set up, as long as shims or eccentric bushings are kept in the same location and orientation they generally do not need adjusting.

A few years ago our boy scout camp had a 1987 F250 4WD truck. it was horrible on front tires and a bear to drive on the highway (take your hands off the wheel and it would dive toward the left immediately). I asked a friend who owned an alignment shop for suggestions (the left front wheel was visibly tilted out at the top). He told me how to use a couple of matched 2X4 blocks and a level on a level floor to set the camber. It was way off, took the bushings out to get the numbers and decided to flip the camber (outer) bushing around. Torqued everything and had the ranger back out and pull back in. Recheck, camber was 0° as near as we could measure (level showed wheel vertical). Then it was time for the old string toe-in gauge, truck was toed out about 1/4". I think he had me set it to 1/8" in max, slightly less depending on where I could get the string to. Truck drove like a new one after that.

I had a 1958 F100 that I put a 312 Y-block and Borg-Warner T85/OD 3 speed into in place of the 223 and 3 speed. That lowered the front a bit and I would occasionally get the "death wobble" due to little or no or possibly even a negative caster angle. I was in Pep Boys and saw some 1/2 length helper springs for leaf springs, bought a set, installed them on the back (shackle end) of the front springs, raising the front of the truck and tilting the axle with it's king pins back enough to give me enough positive caster to solve the "death wobble" issue.

Camber changes pretty dramatically on my truck when reversed into a space.

I was trying to say ^^^above^^^ that a solid axle once set up won't change as long as it keeps the same orientation.

If you change the truck rake just shim it back to normal with pinion wedges.

[Rusty_S85]

If you put springs up front to raise the heigth such as a leveling kit you will have to have an alignment done regardless as has been stated above.

How ever on the spring aspect I would get with someone to make you some springs vs buying off the shelf springs. If you buy off the shelf they wont be made specifically for your truck but a generic spring that will fit and work. Secondly they wouldnt be a lift spring to raise the height some, most leveling kits use just a spring booster that sits between the spring and the mount to create the raise in height and I would not recommend doing this as it will make your truck ride a bit rougher than if you had left it stock height. I would go with a longer spring as it will actually help the truck to ride a bit softer. I noticed this first hand at work doing lift kits and noticed the spring booster lifts always rode rougher than stock and the ones with longer springs always rode softer than stock.

It is what I will be doing on my truck, I will take it in to get a print out first of what the alignment specs are currently then rip it apart for ball joints and custom built springs from Eaton Detroit Spring for my specific truck with a 1 1/2"+ height over stock for the leveling kit effect. Mainly doing it cause my rear leaf springs are worn and the truck sits level now and I will be replacing them and I like the level look for a flare side over a raked look. It also will help stop my passengerside 31x10.50-15 KO2 tires scrubbing my inner fender when I hit a bump with a passenger with me.

[3WVNflip]

If you put springs up front to raise the heigth such as a leveling kit you will have to have an alignment done regardless as has been stated above.

How ever on the spring aspect I would get with someone to make you some springs vs buying off the shelf springs. If you buy off the shelf they wont be made specifically for your truck but a generic spring that will fit and work. Secondly they wouldnt be a lift spring to raise the height some, most leveling kits use just a spring booster that sits between the spring and the mount to create the raise in height and I would not recommend doing this as it will make your truck ride a bit rougher than if you had left it stock height. I would go with a longer spring as it will actually help the truck to ride a bit softer. I noticed this first hand at work doing lift kits and noticed the spring booster lifts always rode rougher than stock and the ones with longer springs always rode softer than stock.

It is what I will be doing on my truck, I will take it in to get a print out first of what the alignment specs are currently then rip it apart for ball joints and custom built springs from Eaton Detroit Spring for my specific truck with a 1 1/2"+ height over stock for the leveling kit effect. Mainly doing it cause my rear leaf springs are worn and the truck sits level now and I will be replacing them and I like the level look for a flare side over a raked look. It also will help stop my passengerside 31x10.50-15 KO2 tires scrubbing my inner fender when I hit a bump with a passenger with me.

RustyS85, thanks for posting. I am interested in your custom spring idea; the kit I am looking at comes with rear parts that I do not intend to use. But I have yet to confirm that axle pivots offered for 4WD will bolt onto my 2WD, the manufacturers say NO!. Are you planning to drop the axle & radius arm mounts on your project? if you have picked out the drop brackets to go with your 1.5" longer springs please let me know where to source them. thanks.

[Rusty_S85]

RustyS85, thanks for posting. I am interested in your custom spring idea; the kit I am looking at comes with rear parts that I do not intend to use. But I have yet to confirm that axle pivots offered for 4WD will bolt onto my 2WD, the manufacturers say NO!. Are you planning to drop the axle & radius arm mounts on your project? if you have picked out the drop brackets to go with your 1.5" longer springs please let me know where to source them. thanks.

The 4wb twin traction Ibeams are a bolt in if you are making the swap, I played around with the idea of a 4wd conversion but it will be more money than I am willing to spend to convert it properly for how little Id use it.

The spring change I am doing will be just the springs reusing everything else that is OE on my truck.

Front springs I am unsure which one to go with as Eaton offers the MC3404 or MC508. The MC3404 is standard duty w/o AC which my truck was a non AC truck but it did have the larger HD cooling radiator which was standard with AC trucks. The MC508 is a HD spring w/o AC or standard duty w/ AC. Im kind of leaning towards the MC508 as my truck did have the HD radiator so I think it might be safe to assume my truck had HD springs in the front as well. The springs will also be +1.5" above stock to create the leveling that I want.

Rear springs are going to be the ML2749 leaf springs at OE ride height, these are 3/1 leaves just like my truck came with and is a 1,250lb capacity with a 125/226 spring rate. I thought of upgrading to the ML2539 4/1 leaves spring that is 1,660lb capacity with a 159/293 spring rate but im concerned it might not fit right, change the OE ride heigth or possibly result in a harsher ride in the back.

I also plan on replacing the axle bumpers with the Timbren SAS that has a 6,000lb capacity that acts like a over load spring when you start to load the truck down with weight. Eaton carries them under the TMFR150SDE for the rear. They offer it for the front as well but I see no need for having it for the front.

For me I planned on rebuilding my front end as well as I have a pop in one of the ball joints every now and then and I have a set of new Moog balljoints. When I do the springs to raise the front up as well as brand new leaf springs out back I will do the ball joints and then take it in to be aligned. Going up 1 1/2" higher in the front to level the truck out should be with in adjustability with a camber/caster bushing that is if the alignment shop is willing to take the time to figure out which one I need. Considering its all will have been apart before taking in it shouldnt be hard for them to do the job as it should come apart easily.

[3WVNflip]

Thanks for all the details, I will bookmark this for future reference, good info. I found a 2.5" lift kit for RWD and my year from Rough Country, so I ordered it based on my measurements of 3-1/2" top of tire to wheel arch front and 7-1/2" in the rear, trying to end up around 6" in the front. I might have overlooked measuring my coils up front for length compared to stock, it's possible they were shorter from fatigue because this kit increased the tire to arch measurement to 7". the body lines are level with the horizon now and I think the setup has come down 1/2" from where they were when I took it down off the jackstands. the manufacturer says the springs should settle in between 14-15" and I measured them just under 15 today:

they offer another set of coils that are supposed to settle around 13" and I am considering trying them. the other alternative is to install the rest of the the kit (2" blocks & longer U-bolts in the back) but I was not trying to raise the loading height at the tailgate any. the kit seems like a bargain regardless since it includes drop brackets for the radius arms & axles and (4) longer shocks as well. I read the shocks are good from stock length : 0" to 5" of lift so I can use them even if I go back to stock. the shocks on this 50k mile truck looked like Motorcraft originals so those were on my list of things to replace anyway.

without finishing the whole project the 'try to get the front end off the ground' test ride went just fine; it is tracking good, slows straight under hard braking, steering wheel returns to center normally, the steering feels smooth (or even smoother than it was) and it handles bumps without bouncing, pogo'ing or diving. I will leave it as is for a few more test drives before changing anything.

[3WVNflip]

UPDATE: not done yet!

My original title and some of the original post mentioned RWD vs. 4WD lift/levelling parts and I'm not sure we came to a consensus on whether a 4WD lift fits the RWD trucks. I found arkonoffroad.com lists the Superlift K554 4" AND K555 6" lift kits as 4WD but under fitment lists all the 80-96 RWD F150s as compatible. Other manufacturers either didn't list or list their kits as 4WD only. Just a little more data supporting the idea that attachment points on the 4WD and RWD are the same.

NOW on to the UPDATE: the idea has been tossed around that my springs were worn out and 'shorter than stock' so that when I put the 2.5" lift on the front it brought the wheel arch up 3-1/2" instead of 2-1/2". I am now searching for any data that would confirm this idea; my tires measure 27-1/2" from the concrete floor and I measured just under 3-1/2" from the top of the tire to the center of the wheel arch before the lift was done. Does anyone know if there is a compressed spring measurement for these trucks that I could compare to my original spring length? or a wheel arch height measurement that is used to establish the 'stock height'? I am thinking about tossing the original (Motorcraft part tag/labels still on them) springs back on to confirm my measurements.

It's a lot of work but I think 2-1/2" increase up front was the number I want/wanted.

thanks.

[3WVNflip]

IT GETS WEIRD: so I threw the original coils back on and they measured right around 12" compressed length. So if from the factory those were more like 13" then getting 3-1/2" of lift from a 2.5" lift kit on this truck seems reasonable to me. Rough Country sells 1.5" levelling coils for this truck and I ordered a set of those. Wouldn't ya know, they measure 13" compressed (the 2.5" lift kit coils compressed to just a bit under 15") but on top of that the driver's side is 1" less lift at the wheel arch than the passenger's side! so I now have 5" to the wheel arch from the top of the tire on one side and 4" on the other. By my measurements their 1.5" levelling coils produce 1 1/2" less lift than their 2.5" lift coils. Of course the drop brackets could possibly make a difference on where the chassis ends up, ya think if I put the levelling coils on without the drop brackets I would get more lift? If you're not as confused as I am about all this feel free to comment or offer advice! thanks btw, I iirc the passenger's side was 1/2" 'higher' than the driver's side before I started.

[Gary Lewis]

IT GETS WEIRD: so I threw the original coils back on and they measured right around 12" compressed length. So if from the factory those were more like 13" then getting 3-1/2" of lift from a 2.5" lift kit on this truck seems reasonable to me. Rough Country sells 1.5" levelling coils for this truck and I ordered a set of those. Wouldn't ya know, they measure 13" compressed (the 2.5" lift kit coils compressed to just a bit under 15") but on top of that the driver's side is 1" less lift at the wheel arch than the passenger's side! so I now have 5" to the wheel arch from the top of the tire on one side and 4" on the other. By my measurements their 1.5" levelling coils produce 1 1/2" less lift than their 2.5" lift coils. Of course the drop brackets could possibly make a difference on where the chassis ends up, ya think if I put the levelling coils on without the drop brackets I would get more lift? If you're not as confused as I am about all this feel free to comment or offer advice! thanks btw, I iirc the passenger's side was 1/2" 'higher' than the driver's side before I started.

I'm thoroughly confused! Why would one spring be longer than the other? Why....

Have you asked Rough Country? It seems to me like they made a mistake.