I am thinking about putting a rear leaf spring pack together for my work in progress, dana 60/dana 70 equipped 78 bronco and was wondering if the leafs on a 78 are the same as an '85 F250 that had a D70 rear? I want to get rid of the factory lift blocks and add more leaves to the pack. My springs on my 78 have only 10K miles on them and the leaf pack from my F250 parts truck is in nice condition so I was wondering if it would be o.k. to add the half ton leaves to the F250 pack? I don't care about the ride stiffness since I'm making hybrid van captains chair seats mixed with a gas-charged semi truck base. Anyway, both packs are the same length but I just wanted to see if there was any issue with mixing half ton and one ton springs?

 

mind if I ask why you want the stiffer springs? a dana 60(or 70) isn't gonna have to be supported by the springs.

 

you will still need to run some sort of shim to achieve the correct pinion angle. the factory block does this. I would keep your half ton springs and install Dual AAL's in both packs.

Or buy a new leaf pack, but i wouldnt just add a bunch leafs and expect it to peform well. if your wanting more stability look at installing a rear sway bar.

 

So is anyone going to answer my question?

 

Pardon me but duh, I know the springs don't support the axle. What do you think I am? Since the truck is now leaf spring equipped in the front(numerous reasons why) it is at a taller ride height than when it had coil springs thus requiring me to put a lift on the rear end. The truck will not see more than 5,000 miles of road use per year and I am trying to do everything as cheap and heavy duty as possible. I don't care about ride quality I just want this truck to be able to survive WW3 if it ever happens and if I break a leaf, finding a replacement part will be a lot easier with leaves all around.

 

sorry if I offended ya buddy, but I still don't see how it would be any benefit. leafs springs are pretty tough regardless. and just sticking leaves in (if they do fit) will not necessarily lift it enough to make up for the lift blocks. not to mention that you didn't say how much taller it is with leaves in the front.

I am going to assume that you do not have the 250 leaves yet (since you are asking if they will fit but make no reference to actually measuring them), and if you are worried about ww3, i think that a broken spring isn't going to near the problem to find as other parts, not to mention fuel.

and i don't think it was very polite or appreciative to kemicalburns, who made a honest to god suggestion for you to respond with "so is anyone going to answer my question" and then tell me that my statement was rude. this is a discussion forum, not a paid tech line. asking for advice or opinions is one thing, demanding an answer is another. please keep that in mind.

 

I'm pretty sure the heavier trucks just add more springs, the individual leafs (except the added ones) are the same thickness, length, etc last time I looked. You get a few more overload-type springs added, it adds to the ride height MAINLY because of the physical thickness of the spring.

If you're adding lots of leafs, you're basically just doing the same thing as adding a block. At rest even in the large trucks only a few of the leafs are really supporting the weight of the vehicle. I put 3 of the longest leafs (the ones under the ones with the eye) on top of stock f150 leafs and it rose my vehicle less than an inch. If you want to raise ride height, look at the thickness of the spring, or find a very high rate high arched spring (that don't really exist out of add-a-leafs because they tend to be weak)

Anyways, if you can fit the leaf to the pack, there's no reason why it shouldn't be ok. Just try to keep the more curved leafs towards the top, lay them out and make sure they are added in an order that makes sense.. in other words, don't try to put a nearly flat overload on top of a well arched upper spring, you'll break straps and lose all springyness.

Also, for durability id' take a coil over a leaf any day.. leafs break, coils rarely do. I've replaced more broken leafs in my time than coils.. coils start to sag, but leafs always break with age.
Leafs also can annoyingly totally screw driveline angles so badly that you have to finetune it until you get the right pinion angle, or adjust trany/tcase angle. Sometimes that angle has to be adjusted so severely, that it causes oiling issues to your rear diff and other miscelaneous problems. Sure, you can drive with a screwed angle, but you're going to be replacing ujoints every few hundred miles.

Keep in mind, the military needed a good, reliable light truck built, they chose a truck with coil springs. They resort to leafs only in their heavy duty personnel or cargo carriers and I'm sure if they could reliably find a way for manage weight in coils, they would..


edit:

Keep in mind, ride stiffness isn't only about your comfort. These are LIGHT half ton trucks. Even the F150 has beefier parts in sections than the Broncos. F250/350s and bigger recieve extra frame reinforcement at the very least. Those hard hits you don't care about because you have suspension in your seats are going to totally destroy your Bronco over time.

Just because it will fit doesn't mean it it should. If suspension softness didn't add to reliablity, we would all be going for vehicles with super stiff suspension (which usually equals more control, even unloaded) and more money put into dampening at the seat. That isn't the case, soft suspension means less stress on your vehicle parts, everything from the dash to windshield to wheels to frame to drivetrain, etc. Consider dampening of motor, tranny, body (which we all know as Bronco owners, is a HUGE deal) , windshield, dash, etcetera instead of just your butt.

 

pinion angle is no joke, please don't ignore it. I broke my stock blocks, had to have some made because I was tearing up either CV joints and Ujoints every 500 miles. In my 1990, the stock blocks were a good 10degrees, that's significiant! and seriously lessens the life of your drivetrain parts.

 

Why would you assume I don't have the F250 springs yet when I said I was going to use the springs from MY donor truck? The WW3 comment was a hypothetical scenario not a serious comment. I happen to have plenty of spare parts and fuel so don't worry about details of something that is way off topic. Also, who is demanding answers? In case you never passed elementary english, saying "So is anyone going to answer my question?" is a QUESTION and not a demand. Note the question mark. Thats a dead give away of a question, please keep that in mind. Lets not be so sensitive here guy. I'm sorry if I offended you. I wasn't aware that you were such a frail princess. If I could take it back I never would have asked such a naughty question in the first place.

 

I agreed with a lot that you said but this is not true. Lift blocks have a small surface area that contacts the springs themselves and under heavy throttle blocks act as a lever and cause spring wrap. The taller the lift block, the more the axle wrap. A stiff leaf pack and just the stock wedge block for pinion angle will greatly reduce the flex of the leaves under throttle. That is why I'm getting rid of the 3.5" blocks in the first place and adding a few of the thicker leaves from my F250 pack. I plan on leaving the bronco pack the same as it is now with 6 leaves and I'm going to put a few of the thicker, shorter leaves from the F250 under the pack and getting rid of the big lift blocks but retaining the wedge for pinion angle(I am aware that pinion angle is important). This way the truck will still flex some but will be lifted cheaply. Like you said yourself, only the top springs like the main spring with the eye are the supporting ones that mainly deal with the ride quality.
As I said before, if worse ever comes to worse and I need a quick fix in a matter of life or death, I would much rather have to only worry about swapping leaves than coils. I agree that coils are tough(I've only broken a few) but there are more parts to go wrong on a coil sprung suspension than a leaf sprung one. There is more routine maintenance as well with a coil setup.
Anyway, you had a lot of good points about rigidity but keep in mind that I don't plan on using springs from a medium duty truck or anything. I will still have flex since I'm not beefing up the pack to look like something on an F600. Thanks for your input. You are one of the very few guys I have ever got a reply from on this site that has reading comprehension skills. No joke. The rest of them seem as if they are recovering from a lobotomy.

 

yeah, good point about them being blocks but with added safety. I still think you're gonna have to worry about wrap and stuff if you stack too many of the overloads. Even those of us running high springs with no blocks have to deal with axle wrap. The further the center of force on the spring is away from the spring eye, the more wrap you'll have.

though honestly, this is only if you're raising it like 4 inches or more, you're not gonna have any kind of trouble with a short pack of leafs. At first I was picturing you with a big 15 leaf pack like you would see on the really big trucks, but with only a couple of flexy f150 leafs to support them all.

and to be honest, I didn't know how to do an oil change when I first started reading this site. If it wasn't for the guys here, I'd probably still be trying to figure it out :P
I dunno how many times good advice here from them have gotten me out of a jam

 

sigh; I hate getting into debates on here. without being able to listen or see somebody leaves too much to interpretation. i'm not trying to argue, just defend what I had interpretated. please let me explain farther:

this can be taken two ways, anger or sarcasm

this irked me because kemicalburns had just given you an answer, and told you to use a couple add-a-leafs. If somebody asked me a question, got an answer, and then asked if i was going to answer their question. I would probably tell them to ask somebody else if they were going to ignore me. maybe his answer wasn't specific enough, but we wouldn't know unless you said so. if that was the case a better response (in my mind) would have been "thanks Kemical, but that didn't quite answer my question. I was wanting to use some ofthe 250 leaves that I had rather than forking out money for AAL's. I measured them and they are the same size. do you think they will work?" it looked like you didn't acknowledge his post at all and just went straight to bashing on me.

the only thing that I have to say to this is that resorting to name calling is immature just about anyway that you look at it, and I think its possible for us to solve our differences in a better way. if not, it won't hurt my feelings, I will unsubscribe from this thread and leave you alone if you wish.

I really wish that you would have had this in the first post, it better explained what you are trying to accomplish. I had the same picture as ErrorS, a bunch of leaves stacked on each other for "strength"

 

Well I'm glad they were able to help you but in my case it's like talking to a wall with these guys. I have decades of vehicle experience under my belt and whenever I simply ask one question and one alone, I get tons of know-it-alls speaking up about related topics that I am either already aware of or not concerned with for my application. I get it that some want to help but others just want to flex their knowledge without even knowing the whole scenario that I am in. It's just kind of annoying when I am looking for one answer and one alone and end up hearing dozens of posts for dozens of weeks and not getting the ONE answer I was looking for.

 

give us the whole scenerio in the first post then.

the rear leave springs from 78-97 are all 3"s wide to my knowledge so you can use springs from any ford 1/2 to 1 ton. Now i am not sure if there is any lenght difference between the springs in question.

 

SIGH..See guy, the problem here is that this is NOT a debate. In order for a debate you must ask a question that can be interpreted through different views and lines of reasoning. I simply asked "Anyway, both packs are the same length but I just wanted to see if there was any issue with mixing half ton and one ton springs?" I wanted to know about mixing spring ratings and that alone. Kemicalburns then went on to give his opinion of what he THINKS I should do to lift my truck when that was not the question. That is why I asked if anyone was going to answer my question because nobody at that point had. For you to side with him when he clearly did not answer my question brings into question your ability to comprehend what you are reading. Also, calling you a princess has nothing to do with maturity it was a joke because you take things so seriously. Things that are not even an issue open to debate. That is what IRKS me!
You then go on to say, "I really wish that you would have had this in the first post, it better explained what you are trying to accomplish" when I went on with detail regarding my plan. Once again, this has nothing to do with my original question of "I just wanted to see if there was any issue with mixing half ton and one ton springs?" What I plan on doing with those springs was not the question and I really wish people would stick to the question and not give their 2 cents unless asked for it. I don't voice my opinion unless someone wants it and I wish others would do the same. Thats what irks me.
First you think me asking the question, "So is anyone going to answer my question?" is a demand, then you go on saying that my question had been answered when it clearly wasn't. I'm quite curious to see how bad you misinterpret what I just now wrote or better yet, just do what you suggested you do; "I will unsubscribe from this thread and leave you alone if you wish." That sounds good to me since you have not done one thing to help and continue to argue over something that is not what the thread topic is about anyway.