Believe me, I've searched for this answer, and haven't found it. The question - why can't factory forged Ford twin I beam axles be dropped in the time honored heat/stretch technique used for dropping other axles? I'm aware that one could cut coils, then have the beams cold bent back to alignment to get a couple inches. And there are thousands of the fabricated DJM dream beams out there as well, so while they look a bit funky, they apparently are satisfactory. Thanks in advance!
Since you brought up "dream beams", as someone who has installed more sets of dropped I-beams than most, I can safely inform you that "dream beams" are garbage, and nothing else. They are just tubes butt welded together, not even slid into one another. Always thought they looked scary, and once you have one break you will understand just how much garbage they are. I have a pic of one laying on my table in two pieces.
Just move the i beam pivot point up 2.5". And cut coils accordingly. Should yield about a 5" drop. The center crossmember will have to be clearanced. I have a 66 f100 im about to do this to. Ill post photos and do a write up.
Although they are easy to do, i think they are too wide.,really limits the wheel choices.,industrial chassis dakota crossmember would be the way to go
Depends on the year that it is going into, and the donor. But yeah, Industrial Chassis is where to go.
Thanks for all the replies - but I'm still curious about the original question, why can't (or why doesn't anyone) drop the factory forged I beams?
Probably just lack of demand. Each side of the twin I beam is much heavier than an early Ford axle. It's possible that the left and right sides are built differently. Have to bend a lot of them to cover the cost of the tooling. There are some heavy truck shops that can repair beam axles. I would make some calls in your area. Sent from my iPhone using The H.A.M.B. mobile app
Its the geometry. The pivot point of the axle would have to be changed, if you raise the spindle then you have to raise the pivot point by the same amount, if not it'll bumpsteer.
The best thing to do with the twin I beam suspension is remove it from the vehicle. It was a bad idea from the start.
A drop of 2-1/2" per side would result in a min 5" narrower track - looks aside, wheels that much closer to the frame would hamper turning radius, etc.
There are a number of off-road setups for raising these, and increasing travel. While this does not directly apply in result to what we are talking about here, it does clearly illustrate the extensive changes changes necessary to both the suspension and the steering on these setups in order to alter the geometry. In short, it is not worth it. Given all of the other aftermarket, and adapted OEM options to swap in, why would anyone bother? A properly designed and executed, safe lowering system for these would cost more than any of the aforementioned, and be harder to install. Suspension and steering are not guessing games.
I certainly wouldn't be bothered trying to modify them because, as Gimpyshotrods said, too many cheaper and more common alternatives are available. However...I owned a customized 73 Econoline years ago that drove and handled great. No excessive tire wear either. My Uncle has a 76 Customized Econoline since 1977 and it also works and drives great. I've never experienced any displeasure from TwinIbeam at all. Maybe it was because both our vans were basicly always carrying the same load, while others, who experienced problems, were empty or fullyloaded at any given time? I dunno...just strikes me as strange.
Move the pivot points some, trim the coils some, raise the coil towers some to equal a 4" drop. These things bumpsteer from the factory so bad you won't notice a difference in handling. Twin I beams like a lot of caster so you are usually good there too. To get camber in order you'll need to bend the beams, find an old school alignment shop or make your own one of these. I've bought drop beams before and it wasn't worth the near $600 I dropped on them so on my current ot '70 Truck I did what I described and just moved shit around. It works fine and my wallet is happier. Sent from my SM-G930V using The H.A.M.B. mobile app
If you have dropped beams then the spindle will be farther up this will cause the main tie rod to be angled upwards to the passenger side and also cause the secondary tie rod to be out of line with the pivot point of the driver side axle. This will cause excessive wear the the driver side tire as it will cause constant toe change due to bump steer. The way to get around this is to lower the steering arms to match the drop so that the tie rods line up with the pivot points of the axles. Another option is to as someone else said to lower it by moving the pivot points up on the frame and cutting the coils or extending the coil towers up to match. After doing this the pitman arm will also need to be raised by bending to line the tie rod end up with the pivot point of the passenger side axle. In my opinion twin I-beam is not the best suspension but can be made to work. I have found that it can be quite bouncy but lends itself to dual shocks quite well. You need a lot of control on the rebound side so it doesn't get into the off camber of the over travel. I have not thoroughly looked at moving the pivot points but it looks like it could be a good option. It will definitely lower the center of gravity and raise the roll center and both of those are a plus when it comes to handling. I have owned many of these trucks but never lowered one, mainly because I didn't want to make the steering geometry worse than it was from the factory. I have a 65 short wide box that I am working on and would like to lower it a bit but not too drastic. I looked at the Crown Vic swap but determined that it is too wide in stock form and probably not worth narrowing the subframe and all that is involved with that. I want a decent handling truck that looks and drives well.
I may be biased because I have 5 Fords at my house with twin I-beams but I find them to ride just fine, no bump steer issues to speak of and as long as you keep an eye on the radius arm bushings and pivot bushings they track straight and wear tires fine also. All of ours are OT but a 67, 73, 78, and two 92's, half ton all the way up to 1 ton dually. I think someone hit the nail on the head saying there just wasn't a lot of demand. I'm sure someone would do them for you but I don't foresee anyone starting a business just heating and dropping beams this late in the game. Shipping them for an exchange type service would be a pain and expensive also because of the length and weight.
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